GEO 10 FINALType "Alley RB" into the author space on the Web of Science. You will find lots of pages of refereed scientific literature that Dr. Alley has worked on. What was he publishing on in 1989? (Hint: the older ones are near the back, so use the "pa

Hawaiian volcanoes, where they emerge above sea level, are:

Broad, gentle shield volcanoes, much flatter than stratovolcanoes such as Mt. St. Helens. The low-silica lava from the Hawaiian hot spot flows easily, so the lava spreads out to make broad, gentle volcanoes that look like shields of medieval warriors. Some Hawaiian lava is clinkery aa (pronounced "ah-ah"), but some is ropy pahoehoe (pronounced "pa hoe ee hoe ee"), controlled by subtle differences in temperature, composition, etc. Mt. St. Helens is steeper, higher in silica, and generally has neither aa nor pahoehoe.

The Petrified Forest of Arizona includes a great diversity of fossils. In the picture above, paleontologist Randall Irmis excavates a plate from a specimen of Buettneria. Based on the discussions of evolution in the class materials, it is likely that:

Buettneria is related to, but recognizably different from, species still alive today. Evolutionary theory indicates that living things change from generation to generation, but that all living things are related. Consistent with this, Buettneria is recognizably similar to, yet different from, amphibians still alive today.

You walk down the beach on Cape Cod, where waves have been bouncing shells around, including pieces of moon-snail shells, as shown here. You find 10 identical shell pieces. All 10 look either like A or like B, but not with 5 of each. Instead, 9 of the 10 shell pieces look like one of the pictures (either A or B), while only the 10th shell piece looks like the other picture. It is very likely that this 10th shell piece looks like:

Image B *check image The shell has a hollow side, shown turned upward toward you in B, while in A the hollow side is down. Waves tend to flip shells hollow-side-down, so moon-snail pieces on beaches usually look like A and only occasionally like B.

The gas from the Marcellus shale:

Is produced by "fracking", which uses high-pressure water and chemicals to make new "fractures" in the shale that allow the gas to escape to wells. Water containing special chemicals is pressurized in holes bored through the Marcellus Shale, breaking the rocks to make pathways that allow the gas in the rock to escape through the holes to the surface, where it can be sold.

What is accurate about the scientific theory of evolution today?

It is being applied successfully in the real world in many ways, including helping fight new disease organisms, and even guiding the thinking of computer scientists. As antibiotic resistance appears in disease organisms, evolutionary biologists are helping doctors find better strategies to keep us healthy. The processes behind evolution—try new things, keep the ones that work, repeat—has been used intentionally for guidance in many human endeavors, including "evolutionary computing" in computer science. Ecologists trying to rescue ecosystems are informed by understanding of the evolutionary processes that made, and are changing, those ecosystems. Even regulations for sport fishing are guided by our understanding of evolution. In the same way as other successful ideas in science, evolution is useful in many practical ways in the real world.

Look at the picture, which shows a small section of a "fossil" sand dune (a sand dune in which the grains have been "glued" together by hard-water deposits). When the dune was first deposited, which was down (which letter is closest to the arrow that is pointing in the direction you would have looked to see the ground when the dune was deposited)?

*CHECK PICTURE A Just above the letter "C" there is a small unconformity. The layers above are cut along that surface. Layers must exist to be cut, so the layers above that surface are older, the lower layers are younger, and "up" was toward the bottom.

Pictures 1 and 2 show two very different looking rivers. What can you say about them?

1 is a meandering stream with clay-rich banks, and 2 is a braided stream with sandy or gravelly banks.

Evidence that glaciers were much bigger about 20,000 years ago than they are now includes:

20,000-year-old deceased shallow-water corals occur in growth position far below the surface on the sides of oceanic islands. The land with the unique glacier marks was pushed down by the ice and now is bobbing back up, water returned to the oceans from the melting ice causes sea level to rise rather than to fall, and taking light water out of the oceans to grow ice sheets causes the remaining waters, and the shells, to be isotopically heavy. But, the dead corals in growth position down the sides of islands are evidence for the ice age.

If all the water that falls on central Pennsylvania's Happy Valley in a year as snow or rain stayed here as water without being used or evaporated, if spread uniformly over the land, it would make a layer about how thick? (Pennsylvania gets about the same amount of precipitation as the average for the world.)

3 feet. A typical rainfall supplies about an inch of water, or just under 0.1 foot. 30 feet of rain would be a big storm every day, about equal to the wettest place on Earth, and while sometimes it may seem the rain in Pennsylvania will never end, there really are clear days. 0.3 feet is a mere 3 or 4 rainfalls per year, and is a dry desert. 0.03 feet would be the driest place on Earth, and 0.003 doesn't occur on Earth. 3 feet is a nice number, and is correct.

You start with 400 parent atoms of a particular radioactive type, which decays to give stable offspring. You wait just long enough for three half lives to pass. You should expect to have how many parent atoms remaining (on average):

50. After one half-life, you've gone from 400 parents to 200; after a second half-life you go from 200 parents to 100, and after a third half-life you go from 100 parents to 50. (Typical studies of radioactive decay use many more atoms, to avoid statistical fluctuations, but the question says "on average", so we asked you about 400 rather than 400,000,000,000,000 to make the math easier.)

The great diversification of shelly fossils that marks the beginning of the Paleozoic Era occurred about:

570,000,000 years ago. Humans were trotting around 57,000 years ago. 570,000 years is barely enough time for evolution to have changed large animals a bit, and although 5,700,000 years is enough time for noticeable change of large animals—increase in maximum size of members of the horse family, for example—the huge changes since the dinosaurs needed a bit more than 57,000,000 years (dinosaur extinction was about 65,000,000 years ago). The Paleozoic came before that, and 570,000,000 years is about right. 5,700,000,000 years is more than the age of the Earth, and so doesn't work very well.

In the first picture, Dr. Alley is pointing to a brownish zone exposed in the low bluff along Coast Guard Beach, Cape Cod National Seashore. The brown zone is rounded on the bottom, flat on the top, rests on sand and gravel, and has sand dunes on top. In the lower picture, Dr. Alley is showing that the brown zone contains twigs and other organic material. What is the brown zone doing here?

A block of ice from the glacier fell into an outwash plain deposited by the glacier's meltwater streams, and the ice later melted to leave a lake, the lake filled with peat and other organic materials, and was later buried by sand dunes, with erosion of coastal bluffs now exposing the deposit. Cape Cod is a creature of the glaciers, and most of the Cape's lakes started by melting of buried ice blocks. Twigs are not brown algae. Arms of the sea are usually a bit bigger than this, although there was a big lake trapped in what is now Cape Cod Bay by the ice. And we have to wonder, is there a rock band named "Whale poop"?

Near Aaronsburg, PA, a company wanted to start a limestone quarry, and planned to pump lots of water out of the ground to make things fairly dry near the quarry so it wouldn't fill with water. Concern was raised—would this affect the nearby trout streams? So, a little harmless dye was placed in a sinkhole next to the proposed quarry, and a fire-engine pumper added a lot of water to the sinkhole. How long did it take, or will take, for the dye to reach the trout stream?

A few hours to days. The dye showed up in a few hours, and the quarry was not excavated. Sinkholes often connect directly and quickly to underground caves or big cracks, and thus to streams, allowing rapid drainage. There are rock units that would hold their water for centuries or millennia, but such units have small spaces, not caves and sinkholes. Local sinkholes do drain to trout streams, and Michigan has to make their own water pollution because water pollution from Pennsylvania does not reach them. (Fun thing to do if you're bored: fit this question into the Michigan fight song.)

The above picture shows:

A glacier, which is generally flowing toward you, carrying rocks picked up from the ridges; the yellow arrow points up one of the stripes of rock, and you can follow the stripe to the ridge where the rocks started. The glacier picks up rocks from ridges, and carries those rocks along to eventually dump those rocks in moraines. The ice is flowing down its surface slope toward you.

Which is accurate about the Grand Canyon, in Arizona:

A great thickness of sedimentary rocks exists in Death-Valley-type faulted basins, which can be seen deep in the canyon in many places. Well over two miles of Precambrian sedimentary rocks can be seen in the deep part of the canyon, all slanted from horizontal and preserved where they were dropped by faulting. The sedimentary rocks above are right-side up, and the Coconino Sandstone is well below the Kaibab Limestone of the rim, which slants down to the north beneath the rocks of Zion, which are older than the rocks of Bryce, among others. Many unconformities exist in the walls of the Canyon, including the one below the Precambrian sediments and the one above those sediments. The idea of the river narrowing over time was the hypothesis that an interested tourist presented to one of the professors and a ranger at the Canyon a few years ago. When the professor asked whether the tourist would want to go out on a narrow point with a jackhammer, the tourist said no, because the rocks might fall off and slide down into the Canyon. When the professor pointed out the many places that rocks had fallen off and slid down, the quick-witted tourist figured out that the Canyon has been widened by such rockfalls as the river has cut downward.

Look at the picture above. What happened here?

A great volcanic explosion occurred, spreading material across the landscape and leaving a hole. Nature has many ways to make holes, and many other ways to make mountains. Part of this class is learning to read the clues, just as geologists do. We saw at Death Valley that the faults tend to make straight lines. Streams on glaciers are not nearly this big, nor are river bends. And while George is cute, he could never dig such a hole. This is the aftermath of the eruption of Mt. St. Helens.

What can you learn about past environments from sediments and sedimentary rocks?

A huge amount, including whether the environment was land or water, whether it was warm enough for crocodiles or cold enough for ice, and much more. From the size, shape and arrangement of grains, the type or rock, the fossils, and more, a great amount can be learned about the environment that existed when the sediment was deposited.

When scientists agree that a particular scientific theory is a good one, and the scientists use that theory to help make new things, cure diseases, etc., that "agreement" came about because:

A number of different experiments by different people all had outcomes that were well-predicted by the theory. Agreement on scientific theories is a contentious, drawn-out, and sometimes acrimonious business. Scientists are no better (and no worse!) than everybody else: we think we are right and those who disagree with us are dunderheads! I put forward my idea, and the experiments that I did that show the idea is a good one... then everybody else piles on and pooh-poohs my idea. BUT, they go out and do experiments that try and show my ideas are wrong... and they can't do it! So eventually all those experiments accumulate, and finally people agree that my idea is a good one. (Sometimes accompanied by a sneer: "...but of course I knew that all along. I just didn't bother to publicize it..." I told you, scientists are no better and no worse than the rest of the world.)

You see a hot-spot volcano on the surface of the Earth. What is under this volcano?

A rising tower of hot rock from deeper in the mantle, and perhaps all the way from the bottom of the mantle. Earthquakes make sound waves that go through the whole Earth, and go slower through hotter, less-dense rocks. By setting out listening devices called seismometers around the Earth, and listening to the waves from many earthquakes in many places, scientists can map the hotter regions, and find that towers of hot rock come up from way deep in the Earth in some places. But, some other hot spots, while clearly coming up from below, don't seem to start quite as deep.

The pink arrows point to a barrier beach, formed when waves fromthe ocean (on the left) washed away mud and piled up sand, after themud and sand were delivered by the stream flowing in from the upperright. The yellow arrows point to interesting features. How did they form?

A storm broke through the barrier beach and pushed sand farther inland. Barrier beaches are piled up by waves, but especially strong storms often break through the beaches. Some of the sand at such new inlets is moved toward the land, often forming new beach-like deposits such as those indicated by the yellow arrows. Some sand is also often moved offshore into deeper water. The river would have buried or reworked the yellow-arrowed features if the river flowed over them, there is no sign of a sinkhole, and bars in the river can be seen to be lower and elongated, not on top and transverse as the yellow-arrowed features are.

The peer review process, in which scientists submit write-ups of their ideas and experiments to a set of colleagues who judge how good the ideas are before the ideas can be published, is:

A useful and important, even if imperfect, mechanism of quality-control for the scientific literature. The peer review process applies to scientific publications and works like this: I get an idea and do some experiments to test it and write down the results of the tests. I send the paper to a scientific journal (Nature, Journal of Geophysical Research, etc.) and the editor of the journal sends it to a number of other scientists who can best judge whether my methods are good, whether my results are new and interesting, and whether my paper ought to be published. They don't base their judgements on whether they like me or not or whether I'm a nice guy/gal or not (or at least they ought not base their judgments on that, though it does happen: we're human!). They don't base their judgements on whether my ideas are popular or unpopular. They are only supposed to ask: is this really new (i.e., did somebody else think of this and publish it already somewhere else?) and are the methods used accurate and repeatable?

Look at the picture above which shows a region just less than a foot across, of a stream deposit from the base of the same pile of rocks that show up in Bryce Canyon. This picture was taken in the face of a cliff in Red Canyon, just west of Bryce Canyon National Park. A indicates a piece of limestone that has been rounded off in a stream; B indicates a mass of sand glued together by hard-water deposits, and C indicates another such mass of sand glued together by hard-water deposits . In order of time of formation, they are:

A was formed first, then B was glued together by hard-water deposits, then C was glued together by hard-water deposits. The clast A existed before it was included in a conglomerate glued together by the sand and hard-water deposits of B, so A is older than B; the whole reddish clast containing A and B is glued into another conglomerate by the sand and hard-water deposits of C, so C is youngest of these three.

Carbon dioxide, CO2, is an important greenhouse gas. Greenhouse gases warm the Earth primarily by:

Absorbing some of the infrared radiation emitted from the Earth. CO2 has very little interaction with the ozone, which is not big on cooling the planet anyway, and CO2 does little to the sunlight reflected from the Earth. But CO2 does absorb some of the infrared radiation emitted from the planet. Absorbing an infrared photon puts a CO2 molecule into an excited state, and fairly quickly the molecule returns to its unexcited state by emitting a photon of the same energy. Some of those photons emitted by excited CO2 molecules head back toward Earth (the emission direction is random). So, the CO2 serves to trap energy in the Earth system, warming the planet so that it glows more brightly to shove infrared radiation past the CO2, achieving a new balance.

Which of the following was probably important in contributing to extinction of most species at the same time the dinosaurs became extinct?

Acid rain, from sulfuric acid from the meteorite hitting sulfur-bearing rocks, and from nitric acid from the heat of the meteorite burning the air. The acid rain very likely did occur, at levels far above those from human-produced air pollution. The meteorite impact was not nearly large enough to move the planet notably or to roll the planet over. Silicosis is a lung disease caused by breathing too much silica-laden dust; other dust materials are typically more damaging, but too much of any dust can be bad. Dissolution in water does not cause lung disease. (Just for your information, some dictionaries list the long version of one form of the disease, pneumonoultramicroscopicsilicovolcanoconiosis, as the longest word in the English language.)

Air moves in from the Pacific, over the Sierra Nevada (a mountain range), and down towards Death Valley. What happens?

Air moving down the east slope toward Death Valley is compressed, and warms by about 5 degrees F per thousand feet downward. As the air moves down, it is compressed and warms, by about 5 degrees F per thousand feet downward.

Humans (and our crops and pets and farm animals) now use:

Almost half of the things the planet makes available and that we like to use. We have removed perhaps 90% of the large fish in the ocean, and we raise crops or cut trees on much of the land surface. In very round numbers, we are approaching use of half of everything available on the planet, with the likelihood that we will greatly increase our population in the future.

What is accurate about the planet's climate system?

Almost the same amount of energy is received from the sun as is sent back to space, but shortwave radiation is received and longwave radiation is sent back to space. Energy in equals energy out, to very close approximation. We actually send back the tiniest bit more, because the Earth makes a little energy radioactively and because we are mining stored energy (fossil fuels) and burning it, and some of that goes to heat the atmosphere but some is lost to space. But, these differences are tiny tiny tiny. (Lie in the sun on the grass on a hot day, and see if you can tell whether the sun or the Earth is supplying the most heat to your skin...). We receive shortwave—visible light—and send back longwave—infrared.

Death Valley National Park preserves the lowest-elevation, hottest piece of the U.S. The park is fascinating for many reasons. What is accurate about volcanoes and Death Valley National Park?

Although no volcanoes are actively erupting at the moment this is being typed, eruptions have occurred in the geologically recent past (the most recent centuries or millennia), demonstrating the presence of hot rock at shallow depth beneath the valley. Death Valley, and many of the surrounding parts of Nevada and California, have experienced geologically recent volcanic activity. This is one of the problems facing the plan to put nuclear waste in an underground repository in Nevada and leave that waste—are we sure that a volcano won't erupt through the repository? There has not been enough lava erupted to fill the valley, however, nor do volcanoes erupt Diet Pepsi (although you can make a nice volcano model by quickly popping the top of a hot, shaken can of pop).

The picture above shows: *CHECK PICTURE

An upside-down dinosaur track. This is a dinosaur track, from Dinosaur Ridge, and the dinosaur stomped down into the mud, so the track is upside-down; the instructional team used the power of modern computers to invert the picture.

In the photo above, the letters A and B are in bowl-shaped features in east Greenland. If you were to walk along the ridge just below the yellow line, you would be balanced on a knife-edged ridge between the two bowls. That ridge is called:

An arête, left between the bowls formed by two glaciers that gnawed into the mountain from either side. This is indeed an arête, between two cirques. The strong layering of the rock material is suggestive of bedrock, not loose pieces as seen in moraines and blockfields. (This is basaltic bedrock from the breakup that formed the Atlantic.) And whoooo, what would the alien use for TP???

Chemists recognize many different elements, such as gold, or oxygen, or carbon, or iron. Suppose you got some iron, and started splitting it into smaller pieces. The smallest piece that would still be called "iron" would be:

An atom We can break matter down into atoms (Greek for "not cuttable" because the Greeks didn't have atom smashers or other exotic tools that would allow cutting atoms into smaller pieces). All of the wrong answers here are smaller pieces of atoms, but they wouldn't be gold any more; you can make any of the elements out of these pieces.

In 2005, Hurricane Katrina brought a storm surge that overtopped the levees and flooded New Orleans, causing over 1400 deaths and perhaps $100 billion in damages. This flooding of New Orleans from a big storm was:

An event that scientists had warned about for decades, based on the known size of hurricanes, and the sinking of the city and the Delta. Scientists and planners did not know exactly when a big hurricane would hit New Orleans and threaten the city, but serious assessments had consistently highlighted the possibility for decades. The failures at New Orleans happened despite the fact that Katrina was NOT the "Big One"—on a scale of 1-5, Katrina was a 3 when it made landfall.

A widely accepted scientific idea usually is based on:

An interlocking web of important experimental results or observations that support the correctness of the idea. At last observation, Pepsi commercials were not highly scientific, even if science is involved in figuring out what sells. It is a romantic notion that you could overturn great knowledge with a single observation; however, observing nature is not easy, and nature occasionally fools us (you can, rarely, flip an honest coin twenty times and get twenty heads), so if a single observation disagrees with a lot of other information, that single observation will be checked in various ways to see if the new result "stands up" before the older body of knowledge is discarded. Before an idea gains wide currency, that idea is tried in various ways, in many labs, in many places in nature, while models are run and theory is developed. The interlocking of all of these provides the confidence that scientists can use in doing things successfully. Although received wisdom from sacred books can be used for inspiration, scientific ideas must be tested against nature. Social scientists have quite rightly learned that scientists are affected by their prejudices, their funding sources, their mating habits, and other things, and that the path of science is not nearly the straight-ahead road to understanding presented in some textbooks. Unfortunately, some of those social scientists have then gone off the deep end and claimed that science is no more useful than any other human story—claiming that astrology and astronomy are equally valid, for example, or palm-reading and modern medicine. These same social scientists seem to know where to find a real doctor when they get in trouble, however. Science is appealed to nature, and builds on the learning of people from around the world. Airplanes that fly, computers that calculate, small devices that make big explosions, etc. are not socially conditioned ideas but instead are demonstrations of the success of science coupled to engineering.

Heating of some materials produces coal. The most-heated is the most valuable. In order, from the MOST-VALUABLE/MOST-HEATED (FIRST) to the least-valuable/least-heated (LAST), the coals (and material that gives coal) are:

Anthracite, bituminous, lignite, peat. This is mostly memorization. But the names hide a lot of history, the peat-bog cutters of Ireland, the brown lignites now being mined in Wyoming, the deep-mines and strip-mines of the bituminous coals of western Pennsylvania, West Virginia and elsewhere, and the hard-coal anthracite of the Scranton and Wilkes-Barre region. If you don't know any of this history, you might consider reading up on it a bit; it is fascinating.

Tsunamis:

Are caused by earthquakes, undersea volcanic eruptions, or anything else that displaces a lot of water in a hurry. Throw a rock in the water, kick your foot in the water, swim in the pool, or even emit flatulence in the water, and you'll see one thing all have in common: they make waves. Earthquakes, volcanic eruptions, landslides, or meteorite impacts in the ocean can make waves big enough that we call them "tsunamis".

Tsunamis:

Are like tornadoes; they can be predicted with some accuracy seconds to hours before they strike in most cases, allowing quick warnings to save many lives. Because tsunamis are triggered by earthquakes, among other things, and we cannot predict earthquakes accurately, we cannot make months-in-advance predictions of tsunamis. The p-waves from the earthquakes that cause the most common tsunamis move much more rapidly than the tsunamis do, allowing timely warnings; however, because the tsunamis get where they are going in hours or less typically, not much time is available. Water does go out before rushing in along some coasts, but comes in before going out along other coasts, waves have "up" and "down" parts, and some coasts get an "up" first while other coasts get a "down" first. Little earthquakes make little tsunamis; big earthquakes make big tsunamis.

The deepest earthquakes are rare, and differ in some ways from the more-common type of quakes. These deepest earthquakes probably:

Are the shaking of the ground caused by "implosion" as minerals rearrange to denser forms as the pressure on them rises in downgoing slabs. "Implosion" is the currently favored idea. As subduction zones take rocks deeper where pressure is higher, the building blocks tend to reorganize to take up less space, shifting from, say, a one-on-top-of-another pattern to a fit-in-the-space-between-those-below pattern. Sometimes, this seems to be delayed and then to happen all at once (I can't move until my neighbor does...), giving an implosion. The biggest, deepest earthquakes happen where temperatures and pressures are so high that we don't think rocks can break. Humans have never made a hole anywhere nearly as deep as the deeper earthquakes. We have mostly quit testing atomic bombs. And, a big earthquake is way bigger than a big atomic bomb. And, no one has ever put a soda machine deep enough to account for the deepest earthquakes.

Regions with mountain glaciers that experience much surface melting in the summer typically are eroded:

At a faster rate than regions with streams but no glaciers. Yosemite Valley, Glacier National Park and other glaciated regions still bear the unmistakable marks of glaciers despite more than 10,000 years of modification by streams. Glaciers experiencing melting change the landscape faster than streams do.

In a glacier, the ice moves fastest:

At the upper surface, where ice meets air. The ice at the surface rides along on that beneath but deforms a bit on its own, and so goes fastest. The fast-food ketchup-packet model in which the mid-depth ice goes fastest would require that the upper and lower pieces be especially strong and rigid (which they aren't; and, it might require someone huge stomping on the glacier). The bed is held back by friction with the rock. And ice lacks the sentience needed to attempt to avoid commercials.

Which of the following is not expected very often near a "textbook" subduction zone (that is, near a subduction zone that is so perfect and free of confusing complications that you would use it in a textbook to teach students)?

Basaltic hot-spot volcanoes such as Hawaii.

The recent changes in the amount of ice on Earth over time occurred:

Because changes in the Earth's orbit have caused changes in the amount of sunshine received during certain seasons at different places on Earth. Milankovitch studied the effect of orbital features on received sunshine, and hypothesized that this may have caused ice ages, but he surely didn't cause the ice ages, which happened long before he was born. The orbital changes have little effect on the total sunshine, but do move that sunshine around, with important consequences. The giant-dust-cloud hypothesis was entertained seriously by scientists for a while but doesn't work; however, like essentially all serious hypotheses that fail, this one is alive and well in the fringe-science web sites of the internet. I'd love to have seen flocks of ptarmigan and herds of marmots, but no one has found their bones, so it is highly likely that they did not exist.

The above picture shows ocean in the upper right, a beach, andland (lower left). The red dashes trace the crest of a wave. Wavesmove perpendicular to their crests. What principle is illustrated by the picture?

Because waves go slower in shallower water, waves turn and move almost directly towards the beach, but the little bit of along-beach motion remaining drives longshore transport. The rotation of the Earth has only miniscule effect at scales this small. Waves do go slower in shallower water, so as one end nears the coast, that end "waits" for the other end to catch up, causing waves to be going almost straight toward the shore when they run up the beach, but with just a little along-beach motion driving longshore drift.

Extinction removes biodiversity, and evolution generates biodiversity. The balance between extinction and evolution controls the Earth's biodiversity. Based on the scientific evidence summarized in the text and in class:

Biodiversity fluctuates about a balance, with short-lived mass extinctions lowering biodiversity and subsequently evolution exceeding extinction over tens of millions of years to increase biodiversity until a new balance is reached. Numerous extinctions have occurred over the history of the planet, but extinctions have been especially rapid during the short "mass extinctions" including the one that killed the dinosaurs. After mass extinctions, evolution fills the empty niches, increasing biodiversity back to a more-or-less stable level.

Some natural resources are renewable—nature produces them fast enough that humans can obtain valuable and useful supplies of a resource without depleting it. Other natural resources are nonrenewable—if we use the resource at a rate fast enough to matter to our economy, the resource will run out because use is much faster than natural production. What do we know about oil and coal?

Both oil and coal are nonrenewable resources, and at current usage rates and prices similar to today, oil will run out in about a century and coal will run out in a few centuries. There is lots more coal than oil; oil has this habit of floating on water, thus rising through rocks and escaping to the sea floor where the oil is "burned" for energy by bacteria or other creatures. The size of the resource, in coal, oil, or anything else, depends on the price, and how long the resource lasts depends on rate of use, which is increasing rapidly for fossil fuels. The idea that immense pools of oil are out there, undiscovered but easy to get, is pretty silly—oil companies are really smart, drilled the easy stuff early on, and are now running out of oil that can be drilled and produced at prices close to modern.

The above diagram is from one of the Geomations in the unit. It shows three possible fault styles. A and B are cross-sections, with a collapsed building on top to show you which way is up—the yellow band is a distinctive layer of rock that was broken by the earthquake that also knocked down the building. C is viewed from a helicopter, looking down on a road with a dashed yellow line down the middle; the road was broken by an earthquake along the green fault, and the earthquake knocked down a building to make the funky-looking brown pile in the upper right.What is accurate about the different earthquake styles?

C is slide-past, B is pull-apart, and A is push-together. Imagine putting the image on paper, cutting out the blocks (one block on each side of the fault), and then sliding them back together to make the original, unbroken features. A and B stand up from the table, C lies down on the table. Now, slide them to make the picture as seen here. In A, you'll be moving the right-hand block up and toward the other block, so it is push-together. In B, you'll be moving the right-hand block down and away from the other block, so it is pull-apart. And in C, you'll slide one past the other (geologists distinguish right-lateral and left-lateral motion for C, but you don't have to worry about that much detail).

Which formula describes the chemical changes that occur and release energy when you start with plant material and then burn it in a fire or "burn" it in a stomach?

CH2O + O2 → CO2 + H2O CaCO3 is shell or cave-rock; the equation with CaCO3 on the left is dissolution of rock to make caves, and the equation with CaCO3 on the right is formation of shells. CH2O is a pretty good estimate of average plant composition; the equation with CH2O on the left is burning of plant material for energy, and with CH2O on the right is how plant material is made. Diet Coke plus Mentos does produce an interesting effect, but this is not the way plants grow.

You watched online as Dr. Alley carved a sand canyon with his finger. Based on what you saw, and on what you know about slopes, stability, mass movement, etc., if a landslide happened someplace last week, you would tell the neighbors:

Care is required; landslides are removing instabilities and moving things towards stability, but a second landslide, or a flood, or other problems are real possibilities. When Dr. Alley made a "landslide", others often followed, but not always. Similar behavior is often observed in nature. The Gros Ventre slide near the Tetons dammed a river, with dam failure later releasing a flood, but a flood was avoided at Hebgen Lake outside of Yellowstone. And so far, we don't think that America's Funniest Classroom Videos is handing out megabucks. But let us know if they start.

One way that sediment is changed to sedimentary rock is by:

Cementation, a process that occurs in nature, and that is similar to processes that can occur in plumbing and other things humans make. Cementation, a process that occurs in nature, and that is similar to processes that can occur in plumbing and other things humans make. Plumbers have big wrenches for a good reason. Water carries minerals, and where temperature or acidity or other things change, those dissolved minerals may be deposited, cementing things together.

The geologic time scale is, starting with the youngest and ending with the oldest:

Cenozoic, Mesozoic, Paleozoic, Precambrian. You could probably reason this out if you remember some Greek roots, or else just memorize it—Cenozoic is youngest, then Mesozoic, Paleozoic, and Precambrian.

Chemical weathering of a continental rock such as granite in a climate such as that of Pennsylvania or other places where a good bit of rain falls, produces:

Clays and rust, that do not wash away easily, and soluble ions, that do wash away easily Weathering of granite in Pennsylvania makes some things (clay, rust, and quartz sand) that stay behind to contribute to soil, and other things (soluble ions) that dissolve and wash away very quickly. In dry climates, not very much rainwater percolates downward and through rocks to streams; most rain soaks in a little bit, but is evaporated back to the atmosphere before soaking way down in soil. Very soluble things (sodium ions, for example) may wash away in the little water that reaches streams, but slightly less soluble things (which would wash away in Pennsylvania) such as calcium will be released from rocks but then accumulate in spaces in the soil as water evaporates. These give rise to pedocals, calcium-laden soils. But these are not expected in rainy places such as Pennsylvania, and this isn't a subject introduced in the course, so you really shouldn't worry about it.

Regarding global warming, most scientists (including those who have advised the United Nations through the Intergovernmental Panel on Climate Change) agree that if we continue to burn fossil fuels at an accelerating rate:

Climate changes will primarily hurt poor people in warm places, but the climate changes are primarily being caused by wealthier people in colder places. Blizzards play havoc with airline travel, which hurts the economy in the mid- and high-latitude wealthier countries. If you have winter (so that warming reduces blizzards), air conditioners (so you can keep the economy humming when the weather is otherwise too hot for office work), and bulldozers (so you can build sea walls or haul things out of the way as the ocean rises), a little warming might even help your economy, although too much warming will be bad. If you are missing any of winter, air conditioning, or bulldozers, all warming is likely to be bad. Most of the world's people are missing all three, and will be hurt by warming, but the warming is being caused primarily by people who have all three.

Which of the following is not a hazard often associated with a single large, explosive volcanic eruption?

Climatic warming. This is one of those interesting cases where "slow" and "fast" are different. Volcanoes release carbon dioxide, and carbon dioxide warms. But carbon dioxide stays up a long time, and no single volcanic eruption puts up enough carbon dioxide to make a detectable difference to the concentration in the air and the temperature of the Earth. However, a single big eruption can put enough material into the stratosphere to block enough sunlight to cool the Earth by a degree or two for a year or two. So the climatic hazard from a single big volcanic eruption is cooling, not warming. Explosive volcanoes are often large and steep, and may have huge glaciers. As heat melts the ice, and as melted rock moving into the volcano bulges the sides, huge landslides and mudflows happen. Tens of thousands of people have been killed in single mudflows. Well over 100,000 people live on the deposit from one old mudflow from Mt. Rainier (and those who know about that Osceola Flow really hope it doesn't happen again!). A tsunami is a big wave, caused by an earthquake, landslide, meteorite impact, or volcanic eruption that displaces sea water. Waves can be 100 feet high or more, and do incredible damage. A big eruption underwater can push a lot of water out of the way, making a tsunami. Pyroclastic flows are major volcanic hazards, and can kill lots of people quickly. Imagine a few-hundred-degree mixture of pulverized rock, glass and poison gas chasing you at a few hundred miles per hour! Volcanoes do put out poison gases, such as hydrogen sulfide or carbon dioxide (a little is good; too much is deadly!). When rocks melt a little, fluid- and gas-making materials preferentially end up in the melt rather than in the remaining rock, so eruptions commonly come with gases, and some of those gases are of types or in concentrations that are not good for nearby humans.

Among fossil fuels:

Coal is made by heating of woody plant material, and oil is made by heating of algae. Slimy algae gives slimy oil; chunky wood gives chunky coal. Works great. Duct tape and WD-40 are the quick-fix tool kit; if something moves but it shouldn't, apply duct tape, and if something doesn't move but it should, apply WD-40. None of you would be so bad as to merit coal in your stocking, but we presume Santa gets it from a mine somewhere.

Heat is moved around by convection, conduction and radiation (and by lemmings carrying space heaters, if lemmings ever carry space heaters). Which statement is more nearly correct?

Convection moves heat efficiently through the soft, hot rocks of the Earth's mantle, but is not efficient at moving heat through the space between the Sun and the Earth. Heat from deep in the Earth is moved up through the soft bulk of the planet primarily by convection, but convection of rocks certainly does not continue beyond the planet, where radiation becomes dominant. In the shallowest, uppermost layers of the Earth, most of the heat transfer is by conduction. And the poor lemmings deserve a rest and a snack.

You find an atom, and you want to learn what element it is (its fundamental type). If you are efficient, you first should:

Count the number of protons contained in the nucleus of the atom. Physicists change the name when the number of charged, massive protons in the nucleus changes. Adding one proton makes a HUGE difference to how an atom behaves, and so deserves a new name. The neutrons hang around in the nucleus to keep the protons from kicking each other out. Exchanging electrons is important, but doesn't change the element type.

Which is the second-oldest sedimentary rock layer?

D The package of sediments C, D, E, and F is upside-down, as shown by the footprints and mud cracks, so C is the oldest one, and D is second-oldest.

Which of the following is part of the modern theory of evolution?

Diversity exists within a species, and "experiments" that tend to promote diversity sometimes occur during reproduction. No matter how hard you and your friends wish that your children will be born with the ability to fly unassisted, the kids will have to use airlines like the rest of us. You can get a tattoo without worry that your children will be born with that same tattoo. A hopeful monster would have no one to mate with. And while sometimes bigger or more-complex kids do better, sometimes smaller or simpler ones do better. But, biological "experimentation" promoting diversity does occur, providing the variability on which natural selection occurs to cause evolution.

In the photo above Dave and Kym are discussing a model of the Waterpocket Fold in Capitol Reef National Park. The Waterpocket probably formed in the same way as the Front Range of the Rockies. This involved:

Especially warm sea floor in the subduction zone off the west coast rubbed along under western North America and squeezed or wrinkled the rocks, folding them (probably with a push-together fault somewhat deeper under the fold). We're still arguing about the West, but it is clear that the west-coast subduction zone, which started with old, cold sea floor going down, slowly warmed as the subduction zone and the spreading ridge came closer together. Warmer sea floor would be more buoyant, and so would sink more slowly, or float better. And that would create more friction, squeezing and rumpling with the overlying continent. As the sea floor warmed, squeezed-up/rumpled-up features developed in the West. So we think this makes sense.

Which is older:

Fault I. Fault I is cut by fault J, so is older than J. Fault J is cut by unconformity K so is older than K. Unconformity K is cut by intrusion G so is older than G, and intrusion G is cut by fault H so is older than H. Hence, fault I is the oldest on this list.

Hot spots:

Feed basaltic volcanoes (composition similar to sea floor), unless the hot spot is altered in composition coming through a continent, in which case the volcano may be more andesitic. The rising hot rock of hot spots feeds volcanoes. Both sea floor and hot-spot volcanoes come from melting a little of the very-low-silica mantle, pulling out the melt, and freezing it, and so are basaltic (low-silica) volcanoes. Note, though, that a few hotspots (such as Yellowstone) are not basaltic, because the basalt has been altered in getting through the continent. The melt probably started out as something that would make basalt, and indeed, the Yellowstone hot-spot track includes basaltic lavas such as those at the glorious Craters of the Moon National Monument. The hot-spot lavas are runny, and spread easily under the air to make volcanoes with gradual slopes, unlike the steep stratovolcanoes, although the slopes of hot-spot volcanoes are steeper under water because the water cools the lava so rapidly that it can't spread far.

The jobs of geologists include:

Finding valuable things in the Earth, warning about hazards, learning how the Earth works, and educating and entertaining people. Most jobs in geology involve finding valuable things: oil, clean water, ores, and more. But, geologists also teach and communicate in other interesting and entertaining ways, warn about hazards, and help understand the Earth system.

As water from rain soaks through the soil, the water typically:

Gains carbon dioxide (CO2) from the air and then gains more carbon dioxide in the soil, becoming more acidic. CO2 is fairly soluble in water. Rain picks up some in the air, becoming slightly acidic. Lots of things living in the soil emit carbon dioxide, and soils contain a lot of carbon dioxide that helps make water more acidic. Humic compounds are picked up from soil by water, and make the water more acidic.

The New Madrid Fault Zone in Missouri has had some surprisingly big earthquakes. A magneto-hydro-astronomer at a small university near the fault zone reports that the gravitational effects of the coming alignment of several planets, together with the weakening of the magnetic field, will cause a giant earthquake on the fault zone on Wednesday morning between 1 and 4 am. Based on materials covered so far in this class, you would be wise to:

Get back to whatever you were doing and ignore the forecast; although there might be a very small effect of planetary gravity or magnetic fields on earthquakes, no one has ever demonstrated the ability to make such detailed forecasts accurately, and many such forecasts have proven to be wrong. By keeping track of where earthquakes happen, combing written and oral histories of past earthquakes, looking at geological deposits to see where shaking has occurred and broken rocks or tree roots or caused sand boils, and measuring where rocks are moving and where they aren't, good estimates can be made of earthquake hazards; but, we can't figure out exactly when the next quake will hit. Planetary-alignment predictions have been made, and have failed miserably. The tiny effect of gravity of the planets on the Earth has not been shown to affect earthquakes at all, although it remains possible that some very small influence exists.

Most U.S. beaches are shrinking or encroaching on the land rather than growing or moving seaward, so the land of the U.S. is getting smaller, not bigger. Causes include:

Global sea level is rising, covering more land. As sea level rises, beaches are pushed landward unless something happens to offset this tendency. Global sea level fell way back in time (from about 110,000 years ago to about 20,000 years ago), but that isn't having much effect on coasts any more. And if the ground were rising from injection wells, then the land would be getting bigger, not smaller.

Which correctly gives the order of the faults, from youngest (first) to oldest (last):

H, J, I I is cut by J, so I is older than J. And with reference to K, both I and J can be shown to be older than H.

The Mississippi River:

Has built a delta, which is several miles thick at its thickest point, from near St. Louis, MO to the Gulf of Mexico over millions of years. Amazing as it may seem, the Mississippi has been taking the debris from the vast area from the Rockies to the Appalachians, and dumping that debris into the Gulf of Mexico, building a pile of sediment that is miles thick in places and extends from St. Louis to the Gulf. The mud has filled an old crack in the continent from when the Atlantic and Gulf of Mexico opened, but the mud doesn't stop the earthquakes that occasionally occur near the tip of the crack. And as for the Yoo Hoo, Yuck!

Which of the following is not part of the evidence that the odd layer marking the extinction of the dinosaurs was caused by a large meteorite impact?

High concentrations of iron found in the layer. We have seen several times that iron is very common, so its presence in a layer would not indicate much of anything. Features really observed in the layer that are associated with meteorites but not common elsewhere in rocks include shocked quartz from the impact, soot from wildfires, iridium from the meteorite, and a giant-wave deposit because the meteorite hit water as well as land at the edge of the Yucatan Peninsula.

Lithospheric plates move on the surface of the planet. Plates meet at long plate boundaries. The types of interactions at these boundaries are very important. Which is NOT an interaction type commonly observed along the length of one of these boundaries?

Hot spot. A hot spot pokes through a plate from below, in some small region. All of the others happen at the long edges of plates.

The pictures labeled I and II show fossils from a sediment core collected from the floor of the Atlantic ocean, east of South Carolina. The sediment has not been disturbed by landslides or mountain building or other processes. The pictures were taken by Brian Huber, of the Smithsonian Institution, using a scanning electron microscope. The two samples in the sediment core were separated by the unique layer marking the extinction that killed the dinosaurs. Which is correct?

II is younger than the unique layer, and thus sat above the unique layer in the sediment on the sea floor. Before the impact, biodiversity was high, as shown in I, which includes fossils from below the unique layer and thus deposited before the meteorite hit. After the impact, most of the living types were killed, giving rise to the limited diversity seen in II from above the unique layer after the impact.

During the most recent ice age:

Ice from Canada advanced across the Great Lakes and into the northern states of the US, but not farther. This is just a fact of geography; the ice came out of the Great Lakes and somewhat farther, but not greatly so.

Icebergs float in water and continents float above the mantle because:

Icebergs/continents are less-dense than the stuff they float in. Flotation and buoyancy are driven by density differences. In general, less-dense objects float higher up than more-dense objects would. Sometimes the density differences are due to temperature, sometimes due to composition. In the case of icebergs, water is denser than ice, so ice floats. Similarly continental crust is less dense than the mantle.

The best description of a scientist's job is that she or he:

Invents new ideas, and shows that some ideas are false. Much of the fun in science is coming up with great new ideas (hypotheses, if you like fancy words). But for your new idea to "win", you have to show that it does better than old ideas, so you have to prove those old ideas false (or incomplete, or not-quite-right, or whatever "nice" word you might prefer). The scientific method is a powerful way for humans to learn to do things, and learn what does and doesn't work, but the results of science are always open to improvement, so are not claimed to be Truth, and probably are not Truth. Some scientists still use pencils and look at things, and there are probably a few non-sexy scientists around somewhere.

The Paleozoic:

Is "old life", the age of shellfish. Paleo goes with Past, and is old life. The Paleozoic started with the "fast" (over a few million years) emergence of many creatures with shells, which greatly increased the richness of the fossil record because shells are preserved so well.

Early geologists did not have radiometric dating techniques, or long layer-counted histories. Instead, they followed William Smith in putting things in order, and then used uniformitarian calculations based on modern rates of processes and observed results of processes in the geologic record. These early geologists, using these techniques, found that the Earth:

Is more than about one-hundred-million years old. Radiometric techniques reveal the Earth to be about 4.6 billion years old, but early geologists did not have the sophisticated instruments to measure the trace radioactive elements and their offspring. Working from the rocks, the geologists knew that the age must be in the neighborhood of 100 million years, plus extra time in unconformities and additional extra time in the oldest, metamorphic rocks.

The above picture is from the Escalante-Grand Staircase National Monument. The pink arrows point along some interesting features. What are they?

Joints, formed when the sedimentary rocks were broken by physical-weathering or other processes. This is the Navajo Sandstone, and it is a sand-dune deposit, but you can't really see that in this picture. Almost all rocks have joints. Joints channel water, and make space for roots, so plants often grow along joints, as you see here. The change from red to white along the upper-left arrow is probably a record of places in the past where fluids carrying oil met fluids carrying water—the water rusted the iron and made red; the oil left the iron reduced and carried it away.

Any region of limestone bedrock containing caves, sinkholes, springs, etc. is called:

Karst. Karst is the region of Slovenia (formerly in Yugoslavia) that has given its name to places with cave-related features. Many, many geological terms have been borrowed from other languages or places, including "geyser" from Icelandic and "tsunami" from Japanese. Permafrost is permanently frozen ground, Pepsoidal is a neologism for "of or pertaining to Pepsi", and scruty is just a word we made up so we wouldn't have to use Pepsi again. Sounds like some bizarre disease, anyway. "Stay back. I have scruty."

These two pictures are from Hawaii Volcanoes National Park, on the flanks of Kilauea Volcano. How are pictures I and II related?

Lava flows chill on top and sides while the unchilled central part continues flowing as shown in II, and if more lava is not supplied to keep the tubes filled, the tubes may drain to leave caves, such as the one shown in I. 2000-degree lava hits 70-degree air on top and sides, and 70-degree rock on the bottom, when the lava first flows out of the volcano, so the lava tends to freeze on all sides. Often, though, the lava will flow downhill away from the volcano fast enough that the leading edge will break as rapidly as it chills, and thus the end won't get plugged, allowing the sort of lava flow seen in II. Stop the supply of melted rock to the volcano end of the tube, the tube drains out, and a cave is left, such as the beautiful one seen in II.

A grand piano in a house in one of the lowest-elevation regions of New Orleans protected by the human-made levees is:

Lower in elevation than a kayaker on the river when the river is carrying its average water flow. In his book on the Mississippi, John McPhee noted that if you could take a supertanker out of the river, keep it at the same elevation but get it past the levees, it would hover over the floor of the Superdome like a blimp. The kayaker is the same; the low parts of the city are below river level even at low-water, and some of the city is below sea level as well.

Silica tends to polymerize in lavas and make them thick and lumpy. Ways to reduce polymerization of silica in lava include:

Making the lava very rich in water and carbon dioxide. The silicon-oxygen tetrahedra link up to make lumps, so anything that gets in the way of this linking will oppose lumping. Iron, water, carbon dioxide, or high heat that shakes the lumps apart can all oppose the lumping of polymerization.

You are told that a region has no glaciers. What does the lack of glaciers tell you about the climate of that region?

Melting removes all of the snowfall. Anyone from Erie, PA or Buffalo, NY, or many other places, can tell you that a snowy winter does not guarantee a glacier, and anyone from the permafrost of Siberia could add that cold does not guarantee a glacier. The way to prevent a glacier is to melt all the snow that falls.

What sort of rock is the dark material very close to the pink granitethat Dr. Alley is pointing to in the picture above?

Metamorphic; The rock separated into layers as it was cooked and squeezed deep in a mountain range. The large crystals, intergrown nature, and separate dark and light layers all point to metamorphism, deep inside a mountain range. Rapid cooling in volcanic eruptions gives tiny crystals, not the big, pretty ones here. You can see the former sand grains or other-sized pieces in sediment and sedimentary rocks. And marmot doo-doo consists of small, dark pellets, akin to big rabbit doots, and usually isn't considered to be rock.

Which is not part of our modern view of geology?

Most mountain building occurs in the centers of lithospheric plates. Most mountain building occurs near the edges of lithospheric plates. All the others are accurate.

A place such as central Pennsylvania, home of Penn State's University Park campus, is fairly typical of the world in terms of rainfall. What happens to the rain that falls on central Pennsylvania each year?

Most of it is evaporated. Water gives life, and life is very good at using water. When their leaves are out, trees use almost all the rain that falls, and tree roots reach down into the ground and pull up some of the water from cold-season rain and snowmelt. An important amount of water does soak into the ground and flow to streams (maybe 1/3 of the total), but plants still get the majority. The amount of water that flows across the surface is increasing as we pave the landscape, but most of the land is not paved, and flow across natural surfaces to streams is small. Streams, lakes and rivers cover only a tiny part of the landscape, so direct rainfall into them is small. "Frackers" are adding other chemicals to water and using it in natural gas recovery, but they are not using nearly as much water as trees. And, while the exact chemical composition of the frack waters is an industrial secret, we're pretty sure that it isn't made of soft drinks!

During chemical weathering, sodium is released as dissolved ions and transported to the ocean, where:

Most of it stays in the water for a while, making the water salty. The "saltiness" of the ocean is primarily sodium chloride, table salt. Most of the sodium goes to make this salt. But, eventually salt beds forming by evaporation of water in marginal basins, or subduction of muds with salty water in the spaces between the grains, does remove sodium from the sea.

Bigger earthquakes occur less frequently, but a bigger quake releases more energy and does more damage. An interesting question to ask about earthquakes (and about almost anything else!) is whether the increase in energy release and damage done is larger or smaller than the decrease in frequency as one looks at bigger earthquakes. Asked a different way, is most of the damage done by the many little earthquakes or by the few big earthquakes?

Most of the damage is done by the few, big earthquakes. An increase of 1 in magnitude increases ground shaking about 10-fold, increases energy release about 30-fold, and decreases frequency about 10-fold; the 30-fold increase in energy more than offsets the 10-fold decrease in frequency of occurrence. We wish earthquakes did no damage, but the millions of people who have been killed in earthquakes over the centuries would, if they could, testify to the damage done by earthquakes. And earthquakes are actually very poor at distinguishing the brands of soda dispensed by or advertised on machines.

Weathering attacks a granite in Pennsylvania or Washington, DC, or a similarly rainy place. The feldspar grains in the granite primarily:

Mostly make clay that stays in the soil for a while, although some chemicals also dissolve and wash away to the ocean. Feldspar gives up some things that dissolve and wash away, but most of the material stays behind, rearranges its structure, and adds a bit of water, making clay that contributes to soil formation.

Geological evidence based on several radiometric techniques has provided a scientifically well-accepted age for the Earth. Represent that age of the Earth as the 100-yard length of a football field, and any time interval can be represented as some distance on the field. (So something that lasted one-tenth of the age of the Earth would be ten yards, and something that lasted one-half of the age of the Earth would be fifty yards.) On this scale, how long have you personally been alive?

Much less than the thickness of a sheet of paper. If the 4.6 billion years of Earth history are 100 yards, then the few thousand years of written history are just one-millionth of that history, just over the thickness of a sheet of paper. And your small piece of written history must be only a small fraction of a sheet of paper, roughly 1/200th or so.

Dr. Alley has helped drill many holes in ice sheets. Special tools can be lowered down the holes on cables, and tracked to learn the shapes of the holes. Initially, the holes are straight up and down. Years later, the holes are bent, because the ice in the ice sheet is flowing. What does it mean to say that the ice is flowing?

Much like rocks in the mantle or iron heated by a blacksmith, the ice is almost hot enough to melt, and deforms as gravity pulls on it, without breaking into loose chunks. Materials warmed almost but not quite to their melting point can deform without breaking or melting. We saw this with the great convection cells in the mantle, back in unit 2, and we meet it again with ice. If you list the temperature of the ice in degrees F, it is a lot colder than the mantle, or iron heated by a blacksmith, or a chocolate bar in your pocket. But, the ice has been warmed from absolute zero almost to the melting temperature, just like the mantle and the iron and the chocolate, so the stress from gravity can cause the ice to deform or flow.

The processes that made Death Valley have been operating for millions of years, and continue to operate today. For this question, ignore the sand and gravel moved by water and wind, and think about the big motions of the rocks beneath. If you had visited Death Valley 1 million years ago, you would have found the valley then to have been (choose the best answer):

Narrower and shallower than it is today. The pull-apart action that is spreading Death Valley and surroundings also involves uplift of mountains or downdrop of valleys, and Death Valley has dropped as its flanking mountains have moved apart. Thus, in the past the valley was narrower and shallower than it is now, and the motions have deepened and widened the valley.

Soil is produced by weathering of rocks, and moved to streams by mass-movement. Our understanding of nature and humans shows:

Naturally, soil thickness reaches an approximate balance, with soil production and loss about equal if averaged over an appropriate time, but human activities have upset this balance and caused soil to thin. Naturally, there is a balance between production and removal of soil over large areas and long times, although over short times the thickness may change. Humans have greatly increased loss of soil through burning, plowing, etc., which is not good for our long-term ability to grow crops. Human pets (including orange-and-white Coral and gray Prancer Alley, seen here in a group hug with Eeyore), do affect things but are not major sources of soil.

If two drifting continents run into each other:

Neither will be subducted back into the deep mantle; instead, they will form an obduction zone. "The Unsinkable North America" might not make it as a vehicle for show tunes, but continents have floated around for 4 billion years and are unlikely to sink in the near future. Old, cold sea floor can sink into the mantle, but continents are lower in density than sea floor and cannot follow. A continent could sink into a subterranean lake of Pepsi One if such a thing existed, but no such thing exists.

Which of the following is not a scientifically accepted statement about the occurrence of transitional forms in the fossil record?

No one has ever discovered a single fossil of any transitional form.

Rocks in continents are on average much older than sea-floor rocks. The likely explanation is:

Old sea floor is recycled back into the deep mantle at subduction zones at the same rate that new sea floor is produced, but continents are not taken into the mantle and so remain on the surface for a long time. Subduction balances sea-floor production very very closely, so the planet retains the same size and density distribution over time. Continents have grown slowly, but once made, the low-density continental rocks stay on the surface, whereas sea-floor rocks are lost to the deep mantle at subduction zones. Geological evidence indicates that we have had ocean basins since just after the formation of the planet. And undersea mining so far has been very tiny and localized.

Suppose that the sun suddenly became a little brighter, which would warm the world a little. Over the next few hundred years, what would you expect to happen?

Other things would change in the Earth system, and these feedbacks would amplify the warming from the sun a little and cause the Earth to end up somewhat warmer than before the sun changed. Negative feedbacks stabilize the climate over long times of hundreds of thousands or millions of years or more, but feedbacks over years to millennia are mostly positive, amplifying changes. If there is a change in the sun, or CO2, or something else sufficient by itself to raise the temperature by one degree, this will be amplified to a few degrees by feedbacks.

What is accurate about seismic waves moving through the Earth?

P-waves (also called push-waves or sound waves) move through liquids, but s-waves (also called shear waves) don't. P-waves go through liquids and solids, because you can squeeze and release a liquid or a solid—push hear and it squeezes a bit, which squeezes what is next to you... and on in a wave. S-waves are a bit like waves on a rope—grab an end and move it sideways, which moves the neighboring part sideways... This works with solids, but not liquids, which cannot "grab" and move the neighboring part.

The pictures show famous volcanoes, that are discussed in the class materials. Which statement is most accurate about these?

Picture II shows a hot-spot-type shield volcano, and picture I shows a subduction-zone-type stratovolcano. Picture I is the glorious stratovolcano Lassen Peak, in the Cascades of northern California, and picture II is the shield volcano of Mauna Loa, on the island of Hawaii.

The picture above shows the stem of devil's club, a plant of the northwestern coast of North America. The native people use devil's club for medicinal purposes. We now know that:

Plants protect themselves in many ways, including thorns but also through chemicals that are poisonous to many things that would eat the plants; those chemicals are sometimes harmful to humans (poison ivy, for example) but sometimes beneficial to humans, and have given us many of our medicines. Most plants have physical protections of some sort (hairs, thorns, hardened parts, bark, etc.), but almost all plants have chemical defenses. Those chemical defenses may kill us if we eat too much, but they also may kill microbes that would kill us before the chemicals kill us. A whole lot of our medicines have come from plants, and there undoubtedly are more to be discovered. There is a race on to find those new medicines before we exterminate the plants containing the medicines. Devil's club has been around longer than Pepsi has.

The above photograph was taken in the Grand Canyon, and shows a cliff that is approximately 30 feet high. What are the rocks in the cliff?

Precambrian metamorphic rocks with some igneous rocks intruded; the folding was caused by mountain-building processes when the rocks were very hot deep in a mountain range. This is the Vishnu Schist and Zoroaster Granite, rocks from the heart of a mountain range. The river is just barely out of the picture to the bottom.

Extinctions have occurred throughout Earth's history. What is accurate about the history of extinctions?

Prehistoric humans cause extinctions faster than is typical naturally, and modern humans are also causing extinctions. Extinction has happened naturally, but humans have greatly accelerated the rate. Early humans caused extinctions, and so have modern humans, with real worries that the rate of extinction will accelerate a lot more in the near future.

The picture above shows a view in the Earthquake Lake region just northwest of Yellowstone.The ramp or slope (often called a scarp) formed in an earthquake.What likely happened?

Pull-apart forces pulled the rocks apart, making the break, and allowing one side to drop relative to the other. The pull-apart forces west of Yellowstone are similar to those of Death Valley, and may be responding to the same broad spreading of the west that widens Death Valley. The two sides moved apart, and then one side dropped relative to the other.

What tectonic setting is primarily responsible for producing the Appalachian Mountains and Great Smoky Mountains National Park?

Push-together Obduction A proto-Atlantic Ocean once separated Africa and Europe from the Americas, and subduction occurred as the ocean slowly closed. Then, a great collision—obduction—raised the Appalachians, bending and breaking the rocks. Later, the mountain range fell apart in Death-Valley-type faulting to start the present Atlantic.

What tectonic setting is primarily responsible for producing Mt. St Helens?

Push-together Subduction Mt. St. Helens sits above a subduction zone, where one tectonic plate goes below another as they come together.

The arrows point to an interesting feature, high in a road cut in the folded Appalachians of western Maryland.What happened here?

Push-together forces broke a layer during folding and shoved one side over the other side. It is always shorter around the inside of a curve than around the outside, a fact well-known to NASCAR drivers and wannabees. The rocks above were folded in the great collision that made the Appalachians, which tends to stretch the rocks on the outside of the curve (near and below the bottom of the picture) and squeeze the rocks on the inside. If the rocks are brittle and don't "want" to flow, they may break, giving patterns such as that shown by the arrows. You can see similar things in many places; if you happen to visit Penn State's University Park campus, such features are exposed in the road cut along the Rt. 322 expressway just southeast of East College Avenue.

What tectonic setting is primarily responsible for producing Olympic National Park as well as the hills on which San Francisco is built?

Push-together subduction. The rocks of Olympic and San Francisco were scraped off the downgoing slab of the subduction zone.

In age dating, geologists use:

Radiometric techniques and layer-counting for absolute dating of events that happened in the last 100,000 years, and other radiometric techniques for absolute dating of much older events. If you want an absolute date (number of years) rather than older/younger, you can count layers for young things, or use radiometric techniques for young things or for old ones.

A dam is built on a river, forming a reservoir. Over time, this likely will cause:

Rapid erosion of sand downstream of the dam, because the clean water coming out of the reservoir will be able to pick up the small sand grains. Moving water can carry sediment. Sediment-free water is released from a dam but often later observed to have sediment, so erosion must be occurring. Loss of sand bars below the Glen Canyon Dam shows that sand is carried away downstream of dams. Dams stops floods that are needed to move the big pieces (boulders, cobbles), and dams cause sedimentation upstream, but not downstream. Our friends from Columbus are probably too cultured to be relieving themselves outside the Mall; besides, the last time I looked during a visit from the Buckeyes, the inebriated people were not straying that far away from the downtown bars.

National Parks are:

Regions containing key biological, geological or cultural resources that have been set aside for the enjoyment of the present generation and future generations. Old Faithful, the giant sequoias, and Mesa Verde's cliff dwellings are waiting for you, and your grandchildren.

Sometimes, people with scientific backgrounds say bad things about religion, and sometimes people with religious backgrounds say bad things about science. This is because:

Religion and science do not need to disagree, but sometimes science-background and religion-background people choose to disagree.

Fossil fuels are usually formed from:

Remains of formerly living things buried by sediments in regions with little oxygen. Where oxygen is present in sediments, bacteria use the oxygen to "burn" organic materials, so oxygen and fossil fuels don't go together. And, Diet Pepsi is rather resistant to decay, and would not make fossil fuel.

Geologically speaking, the water table:

Rises during or soon after rainstorms as spaces fill up, and sinks during droughts as water drains away. As trees suck up water during droughts, air enters spaces where water once was, so the water table (which is the bottom of the region with some air in spaces) must sink in elevation. Creeks do change in elevation between rain and drought (floods happen...), and while there are random elements in the world, this is surely not one of them. (Whenever someone claims something is random, at least suspect that the person is really saying "I don't know what I'm talking about, and I'm too lazy to find out.") And while there might be bottled water in the Capitol, geologically speaking, that is not the right answer.

Globally averaged, the level of the oceans is:

Rising, as warming causes the ocean to warm and expand, and as glaciers melt. Indeed, sea level is rising, by almost an inch per decade. The biggest reasons are melting of ice on land that releases water that flows into the ocean, and expansion of ocean water as it warms up.

Geophysical evidence indicates that convection is occurring in the Earth's mantle. What is the most likely physical explanation for why convection can occur in the mantle?

Rocks deep in the Earth expand and so become lower in density and tend to rise as they are heated, and the deep rocks are warm enough to flow slowly even though they are mostly solid. Convection seems so easy, but describing it in words is not. For "ordinary" convection, one needs something capable of flowing (gas, liquid, or soft solid), heat below and cold above with expansion reducing density on heating and contraction increasing density on cooling, and then a bit of time and a perturbation of some sort to get the motion started. If you had something that expanded on cooling and contracted on heating, and you had cooling below and warming above, you could also make convection work. The mantle is mostly solid, the outer core can't directly stir the mantle or cause convection, and the magnetic field doesn't do much to move rocks.

When discussing earthquakes that happen in the upper part of the Earth's crust, geologists believe that most are caused by elastic rebound. This means:

Rocks on opposite sides of a break, or fault, move in opposite directions, get stuck against each other for a while, bend, then "snap back" when something breaks or gives along the fault. Try sliding a boulder over the ground, and you'll find the boulder gets stuck for a while. Lean harder, the boulder jerks forward suddenly, and you just had a tiny earthquake. Implosion earthquakes probably exist, but the rocks don't bounce back to their original size, and such quakes only can happen deep. We have no information on Graham Spanier's choice in socks, but his choice is unlikely to shake much beyond the immediate vicinity of University Park.

The two pictures above, I and II, show fossils inrocks from the Grand Canyon. Each is "typical"; the rocks near sample Icontain fossils similar to those shown in sample I, and the rocks nearsample II contain fossils similar to those shown in sample II. It is likely that:

Sample I is from high in the cliffs of the Grand Canyon, and sample II is from much lower, near the river. Sample I is a wonderful shell hash, or coquina, from the Supai Rocks well up the side of the Canyon, and contains shells from a great diversity of different creatures. Sample II includes algal-mat deposits (stromatolites) from the Precambrian Chuar Group of the Grand Canyon Supergroup, deep in the Canyon near the river, from a time when biology was not a whole lot more diverse than algal mats. Lake Winna-Bango featured in the gripping Dr. Suess tale of Thidwick, the Big-Hearted Moose, but is not pictured here.

The picture above is of the coast at Acadia National Park. Look at the shape of the rocky island marked with the big "I" in the middle of the picture. The most likely interpretation is that this was caused primarily by:

Sculpting of the rocks by a glacier, which flowed from the left to the right. The side of the rock that a glacier reaches first is sandpapered and rounded blocks are removed. The ice thus flowed from left to right, streamlining and smoothing the island. Wind and waves do not make such distinctive forms, and while Rockefeller stonemasons might have done so, they probably would have carved a huge likeness of a fabled ancestor instead.

In the picture above, the big W is in ocean water, while the little w is in water in a bay cut off from the ocean by the bar indicated by the pink dashed arrow. A stream flows toward the bay along the blue arrow, and coastal bluffs are indicated by the dashed yellow arrow. What probably happened here?

Sediment has been eroded from the land by waves crashing against the bluffs, and the sediment has been transported along the shore by longshore drift to build the bar. Longshore drift is important, and moves much sediment. The greater width of the beach across the mouth of the stream than nearby shows how far waves can go; adjacent to the stream, the waves must cross the beach during storms and batter the bluffs, making sediment that feeds the longshore drift. Submarines are not a big worry in such shallow, near-shore settings, and sinkholes tend to be round, not elongated as seen here.

How is sediment related to sedimentary rock?

Sediment is gradually hardened to sedimentary rock by various processes, and the point where the name changes from sediment to sedimentary rock is somewhat arbitrary. Loose sediments are known to be hardened in just a few years in exceptional cases, but usually thousands of years or longer are required (archaeologists usually excavate old sites using trowels and whisk brooms, not dynamite!). The change is usually gradual, and there is no sudden point at which the name changes.

Humans often try to change coastal processes to benefit us. One of the many things we do is to build walls, or groins, or jetties, to interrupt waves and currents and sediment transport. This example is from the coast of Washington. What has happened here?

Sediment transport is typically from the right, causing deposition to the right of the jetty but erosion to the left A jetty works like a dam, trapping sediment on the "upstream" side and letting clean water pass to the other side, where the clean water erodes. So, the transport is typically from the right. A large beach has been formed there, but erosion "downstream" is cutting around the end of the jetty.

Which of these is an important idea that geologists use in learning which clastic sedimentary rocks are older, which younger, and what has happened to those rocks?

Sedimentary layers start our nearly horizontal. Gravity pulls on loose sediments, so sedimentary layers start out nearly horizontal, not at steep angles or perfectly vertical.

What was going on geologically that caused the earthquake that knocked down much of San Francisco in 1906?

Slide-past motion along a great fault. Not much mountain-building is happening along the central coast of California; the rocks slide past horizontally. The sliver of California to the west of a line connecting San Francisco to Los Angeles is sliding to the northwest, and as the sliver slides, it sticks and slips, making earthquakes.

There are many large mammals on Earth today. This is because:

Small mammals were not able to outcompete the dinosaurs for big-animal jobs, but after the dinosaurs were killed, some large mammals evolved from small mammals to fill the large-animal jobs. There are "big-animal" jobs—eating tall trees, eating smaller animals, etc. But the total number of big-animal jobs is limited. The dinosaurs filled the big-animal jobs before mammals really got going, and mammals were not able to displace the dinosaurs. Some small mammals survived the meteorite that killed the dinosaurs, and then evolved to give big mammals over millions of years and longer. There were almost no big mammals before the dinosaurs were killed off, volition has nothing to do with evolution, and running away doesn't avoid acid rain.

What is accurate about the scientific results learned by counting tree rings?

Study of tree rings and associated geology shows that the Earth is more than 12,429 years old. The longest continuous tree-ring record is 12,429 years, but that was published a few years ago, the trees grew in soil that was already there, and there is lots of older wood around. So, the tree rings show that the Earth is more than 12,429 years. But, we don't have overlapping trees back to the formation of the Earth about 4.6 billion years ago, so tree rings do not show that the Earth is 4.6 billion years old.

Beaches change as seasons progress. A typical change is (note: a breaking wave curls over and the top falls down, making spectacular movie footage if a surfer is in the way; a surging wave hangs together and the top doesn't fall over):

Surging waves bring sand in during summer, and breaking waves take sand out during winter, so summer beaches are large and sandy while winter beaches are small and rocky. Winter beaches are eroded, as breaking waves bring their energy far inland through the air, and the outgoing rush of water removes sand; surging summer waves replace that sand. And if you have ever been in a Nor'easter on the Cape, even hardy nudists would be in danger of losing certain important peripherals.

Suppose that CO2 in the atmosphere was held at a constant, natural level for a few thousand years. Then, CO2 was added to double the atmospheric level rapidly, and this new, doubled level was maintained for a few thousand years. What was the most likely change in the typical average temperature of the planet?

Temperature before the increase in CO2 was a few degrees lower than temperature after the increase.

What is accurate about the "Law" of Faunal Succession:

The "Law" was developed from the observation that using geologic reasoning to put rocks in order from oldest to youngest also put the fossils in those rocks in order. In the late 1600s in England, William Smith discovered that putting the rocks in time order put the fossils in time order, allowing him to use the fossils as a shortcut in understanding the rocks. We will see soon that faunal succession is consistent with evolution but does not require it, does not require but might allow catastrophism, and informed but was not developed by theoretical biologists. Faunal succession was known before Congress was founded, and before Darwin was born.

Geologists get to play with chemistry, physics, biology... and history! And what a history you will meet as you work your way through the course. Starting at the beginning, the textbook provides the scientifically accepted start of the story... and promises that you'll get to explore some of the evidence for that scientific view, later in the semester. Meanwhile, which is more nearly correct of the scientifically accepted view?

The Earth formed from the falling together of older materials, about 4.6 billion years ago. The Big Bang is estimated as having occurred about 14 billion years ago. Stars that eventually formed in the wake of the Big Bang led to production of elements such as iron and silicon that are common in the Earth—we are formed from second-generation stardust, which "got it together" to make the planet about 4.6 billion years ago.

There is a deep trench in the sea floor off the Marianas volcanic arc of explosive, andesitic, Ring of Fire volcanoes in the South Pacific, but the water is not deep off the coast of Oregon and Washington near Mt. St. Helens and the Olympic, because:

The Marianas, Oregon and Washington have had the sea floor bent downward by subduction to make trenches, the trench off Oregon and Washington is filled by sediment eroded from the nearby continent, but the Marianas don't have a nearby continent and so the trench there is not filled with sediment. The more rocks there are nearby, the easier it is for erosion to move some of those rocks. The trench off Oregon and Washington has Oregon and Washington nearby, with lots of rocks. Add in that Oregon and Washington have great rivers such as the Columbia, and huge glaciers that grind up the rocks such as the beautiful glaciers on Mt. Rainier, and there is lots of sediment to fill the trench and be scraped off the subduction zone to make Olympic National Park. The Marianas involve subduction of older, colder sea floor under younger, warmer sea floor, have less rock above sea level nearby to be eroded, are in a warm place without glaciers, and so haven't filled the nearby trench with sediment. There probably are a few discarded floppy disks, as well as a lot of other human-produced material, in the trench off Oregon and Washington, but nature has been a lot more important than humans in filling the trenches. Humans did once talk about disposing of radioactive waste in the trenches, but then we found out that whatever goes down the trench comes back up, and may be squeezed and broken and squirted back up quickly, so we gave up on that idea. And the volcanoes of Oregon and Washington are subduction-zone volcanoes, not hot-spot volcanoes.

Beaches change size with every storm, but if you average over a few decades, the size of a typical sandy beach is usually controlled by:

The balance between sand loss to deep water, and sand supply from rivers or from coastal erosion.

Your boss has assigned you to get the low-down on the latest wonder-drug and to be darn sure to get it right. You would be wise to consult:

The article in the Journal of the American Medical Society, a peer-reviewed scientific journal, reporting on the discovery and testing of the drug. No source of information is perfect, but the refereed articles in learned journals put immense effort into "getting it right". The web has some reliable information, but probably most of the information on the web is not especially reliable. The web is very inexpensive, and lots of people put junk on it. The Wikipedia gets a lot of things right, but it is a distilled synopsis of the real stuff. Most newspapers are around for the long haul, and try to make the news fairly accurate, although some newspapers do have agendas, and the editorial pages are not especially accurate. But, if the report is on the views of a public figure, the newspaper may accurately report what the public figure said, but what the public figure said may be less than completely accurate. And while you are welcome to believe that an unsolicited email promising to grow your ***** will do so... don't count on it.

Which is accurate about the Earth?

The asthenosphere is the soft part of the mantle below the lithosphere. The lithosphere is a layer containing both the uppermost part of the mantle and the crust, where breaking is more common than flowing. The uppermost mantle is cold enough that it doesn't flow easily, so it rides along with the crust in lithospheric plates rafting on deeper, softer asthenospheric mantle. The deepest crust is a bit soft, because at a given temperature the high-silica crust is softer than the low silica mantle, but let's not get too complex here.

People sometimes take machines out into deep water to "mine" sand, and bring it back to beaches. Dumping a lot of new sand on a beach usually causes:

The beach to lose the new sand over the next year or years, as waves and currents move the sand back to deeper water. Waves and currents move lots of sand. If we want to offset this, we need to move a lot of sand, too. Building beaches from mined sand can work, but the sand heads back to deep water quickly, so in most cases the activity must be repeated every year or every few years to keep the beaches large and sandy.

What is the "Ring of Fire"?

The complex of volcanic arcs fed by subduction zones encircling the Pacific Ocean. The "Ring of Fire" is the circle of volcanic arcs fed by subduction zones with scraped-off muds and deep earthquakes around the Pacific Ocean.

If you hike down into Bryce Canyon, and you look up the correct stream bed, you'll see this. The trees lying across the stream bed in the photo above (between the pink arrows) are a small dam. What has happened here?

The dam has trapped sediment upstream, and the clean water coming over the dam has picked up sediment downstream of the dam and lowered the stream bed there. Fast-flowing floods have lost their debris when slowed by the dam, filling the space above the dam with rocks. This basic pattern—dams collect debris and release clean(er) water that can erode more, is seen over and over in geology. And, marmots don't dig that much at Bryce!

The map above shows the Birdfoot Delta of the Mississippi River, where it empties into the Gulf of Mexico. The river is shown in blue, as is the Gulf of Mexico. The river "wants" to leave this delta, and flow somewhere else, far to the west of the area covered by this map. Why?

The delta has built up as well as out, and that makes some other path to the Gulf steeper and shorter than the one now being taken, and during a flood the river tends to take that shorter path and cut a new channel. The river very nearly broke through the Old River control structure in a big flood, to take the shortcut down the Atchafalaya. The long path out to the end of the delta is not very favorable for the river, which has switched naturally in the past and would switch if humans allowed it to.

The picture above illustrates what scientific principle?

The equator is hotter than the pole because the sun hits the equator directly but the sun hits the pole a glancing blow Geometry is the main control on equatorial heating. Although the equator is closer to the sun than the pole, the difference is tiny and matters little to the temperature difference between equator and pole. The rotation of the Earth causes winds to turn as they blow over the surface, but does not heat the air. There is no clustering of volcanoes at the equator, and the heat from volcanoes is tiny compared to the heat from the sun. And we are quite confident that several celebrities and politicians believe that they are the worlds sexiest human being, so Dr. Alleys standing cannot be undoubtedly claimed.

The picture above shows a glacier in eastern Greenland, in the world's largest national park, flowing from mountains at the top of Jameson Land (at the top of the picture) toward the lowlands of Kong Oskar Fjord (just out of the picture at the bottom). Based on what the picture shows, what has happened over the last century or so?

The glacier has become shorter, because of a decrease in snowfall to the accumulation zone (A) or an increase in melting of the ablation zone (B). Accumulation is a building up, ablation a wearing away or loss. The glacier builds at high elevation (A) and wears away at low elevation (B). And, the halo of moraine around this glacier at low elevation shows that the ice has retreated, so a decrease in snowfall to the accumulation zone or an increase in melting of the ablation zone is indicated.

In the photo above, Sam Ascah is standing on sand and gravel in a pothole, where a stream swirls during the short but intense thunderstorms of Zion National Park. And next to that stream, the other picture shows the sandstone and the hang-on-so-you-don't-fall-over-the-cliff chain along the trail. A likely interpretation of these features is:

The grooves behind the chain have been cut over decades by motion of the chain as hikers grabbed it, and the potholes were cut by water swirling rocks around during the rare floods over much longer times. The chain really has hung there for decades, and has been scraped against the cliff dozens of times per day each summer, slowly wearing into the easily broken sandstone. The stream does swirl rocks around and slowly wear down the potholes. The potholes were there beside the cliff when the trail was established, and havent changed too much over decades.

On the Richter scale of earthquake intensity:

The ground is shaken 10 times more by a magnitude-8 quake than by a magnitude-7 quake. One problem in describing earthquakes is that the ground shaking in the smallest one you can feel is 1,000,000,000 times smaller than the ground shaking in the largest quakes. We usually dislike having a scale that requires us to talk about an event of, say, size 100,000,000; instead, if a magnitude-1 quake moves the ground 10 units (say, 10 nanometers at some specified distance from the quake), than we say that a magnitude-2 quake moves the ground 100 units, and a magnitude-3 quake moves the ground 1000 units, and so on. You'll notice that the magnitude is just the number of zeros after the 1; this is a logarithmic scale.

Great Rock really is a great rock on Cape Cod, as shown by Dr. Alley's relatives for scale. The picture doesn't even show all of the rock above ground, and there is as much rock below ground as above. Great Rock sits well north along the Cape, just inland of Coast Guard Beach. Most of the Cape there is sand and gravel. So why is the rock there?

The ice carried the rock here—glaciers carry big as well as little rocks, and can leave big ones even if most of the material carried by the glacier is then sorted in outwash. Glaciers carry rocks of all sizes easily. Cape Cod is the product of glaciers, and almost everything natural on the Cape was delivered by glaciers originally. There rarely are big tsunamis in the Atlantic, but not this big. Nor is there any evidence of a big meteorite impact that is as young as Cape Cod. The east coast is rather free of large earthquakes, although Charleston, South Carolina gets a few occasionally. And the early settlers would not have put such a huge thing in the bottom of their ship (imagine having that bouncing around in a storm!), nor could they have taken such a rock out easily upon arrival.

Dave Janesko holds two rocks next to each other.The black one (to the upper left in the picture) is from a lava flow, and is much younger than the red one (to the lower right in the picture), which is a lake sediment. In nature, these rocks are found the way Dave is showing, with the younger black one next to the older red one rather than being on top of the older red one. This actually is related to Death Valley, although these rocks are a good bit east of Death Valley. As described by Dave Janesko in the online video, what happened here?

The lake sediments were deposited, then the lava flowed on top, and then a pull-apart Death-Valley-type fault formed, breaking the rocks and dropping the lava flow to be next to the lake sediments. The spreading that opened Death Valley affected a lot of the west, all the way over to Bryce Canyon in Utah. The Sevier Fault, just west of Bryce, formed as pull-apart action broke the rocks, allowing younger rocks including the black lava flow to drop down next to older rocks including the red lake sediments. There really are cases where lava hardens in cracks, or where lava flows fill valleys, but a careful examination of the rocks here shows that the lake sediments have not been heated by nearby lava, so these lake sediments and the lava must have been placed together after the lava cooled. Folding does occur, but not here.

In Pennsylvania today (or at most other places on the world's land surface):

The land surface is accumulating sediment in a few small places, building up records of geologic history, but most places are eroding. Today in Pennsylvania (and across most of the land surface of the planet), sediments are accumulating in a few human-made lakes, a few natural wetlands or natural lakes, along some streams and in some caves, but almost everywhere else is eroding. This is the typical state of affairs, so you need to correlate events across large regions to get a good geologic record.

Often, landowners along eroding beaches will build groins, which are walls or dams sticking out into the ocean or lake from the beach. Why are these built, and what happens?

The landowners are trying to catch sediment from the longshore drift to add to the beach; this can work, but often erosion on the "downstream" side of the groin makes the neighbors mad. The "river of sand" that is the longshore drift along the beach is similar to a river in many ways. "Damming" the flow with a groin will trap sand upstream, on the side from which water and sand are coming, but that will allow water with less sand to attack the downstream side, causing erosion there. Dense groin networks may actually so roughen the coast that they hold sand overall, but the erode-the-downstream-neighbors problem is real and often dominates. If you wanted to trap sand going in and out, you would build walls or dams that are perpendicular to that motion, and thus parallel to the beach. And groins are not the best places on which to stand during storms, nor do many landowners actually plan ahead to get good pictures of their houses falling apart in the waves.

What type of mass movement moves the most material, averaged over the Earth's land and over long times?

The many, small events move the most material. As rocks move to streams in many places, such as Pennsylvania, the slow and steady motions are more important than the few dramatic events. Specific places may be dominated by the few, dramatic events, especially in steep mountains, but across the Earth soil creep probably dominates.

Most of the island of Greenland is covered with a great ice sheet, but rocks and soil stick out in some coastal regions, such as the one in this picture in the great Northeast Greenland National Park. The picture above shows a hillslope that is about ½ mile across. The hill slope towards you, so the lowest part of the hill is at the bottom of the picture, and the highest part is at the top of the picture. What is likely to be true?

The materials on the hillside are moving toward you at an inch or so per year. The hillslope in Greenland bears the unmistakable signs of creep on permafrost, carrying streams of rocks and bits of tundra downhill at an inch or so per year. Such processes used to occur in Pennsylvania and elsewhere during the ice age, but are still active in Greenland.

Large rivers have many interesting features, including:

The natural levees, formed when flood waters leaving the channel slow down and drop much of their load near the channel; beyond the natural levees is the flood plain, where much of the rest of the mud in a flood is deposited in a thin layer. Many processes contribute to the formation of flood plains, but deposition of mud to smooth the surface is the most important one. Flood plains often occur beyond natural levees. The initial slowdown as floodwater spreads from a river channel into the trees deposits sediment to form natural levees.

The United Nations-sponsored Intergovernmental Panel on Climate Change shared the 2007 Nobel Peace Prize. The information that the Panel has supplied to policymakers includes:

The observed rise in atmospheric CO2 levels has been caused primarily by human fossil-fuel burning, and very likely is causing warming of the climate that is likely to become much larger if we continue our current behavior.

The above Landsat image from NASA shows Cape Cod, Massachusetts. This is a pile of sand and gravel out in the north Atlantic. The Cape has no large rivers, and is not especially close to any large rivers (the Connecticut and the Hudson are far out of the picture to the left). Looking along the far right-hand side of the Cape, the long white line is sand of the great outer beach (pink arrow), and sand deposits are prominent to the north and south (yellow arrows). What is going on?

The ocean is eroding the outer beach, and the yellow-arrow ends are growing more slowly, so the Cape as a whole is shrinking. You can actually see sand underwater off the yellow arrows, and that sand came from the outer beach—the Cape is losing ground. Furthermore, the Cape is losing ground much faster than nudists are losing peripherals.

Dr. Alley once helped a Grand Canyon ranger answer a tourist's question: "Why is the Canyon wider at the top than at the bottom?" The tourist had their own favorite theory. Based on the materials that have been presented to you've in this class, what geologically accepted answer would Dr. Alley and the ranger have given the tourist?

The river cuts down, and that steepens the walls of the canyon, which fall, topple, slump, creep or flow into the river to be washed away, thus widening the canyon above the river. The tourist suggested that the river has gotten narrower over time. Dr. Alley asked the tourist whether he would ever consider going out on a particular narrow pillar of rock (already teetering dangerously and separated from the walls of the canyon by a huge crack) with a few hundred of his closest friends, and jumping up-and-down vigorously. Predictably, the tourist said "of course not, it might fall over." Dr. Alley then pointed out the many places where rocks clearly had fallen off the cliffs and moved downhill, at which point the tourist quickly switched his opinion to the "down-cutting" river explanation, with the ranger thoroughly enjoying the show.

Stephanie and Topher are standing next to the Colorado River in the Grand Canyon.What can be said of the water here?

The river was naturally muddy, but has been made clear because most of the sediment is settling out in the reservoir behind the dam upstream. Native species that lived in the muddy waters are now in danger of becoming extinct, because the clear water released from the dam makes those fish too easy for predators to see.

The picture above shows a very hard piece of rock about six inches across, in the Grand Canyon. The surface of the rock looks rather different from the surfaces of many other rocks.What made this odd-looking surface?

The river, which blasted the rock with sand- and silt-laden water during floods; this shows that even hard rocks can be eroded by rivers. The Canyon was carved by the Colorado River. Glaciers have not been there, and while wind and faults can change the appearance of rocks, none makes something like this river-polished rock, as you saw in one of the Grand Canyon V-Trips.

The picture above shows an outcrop along Interstate 70 in Utah. The green arrow points to a person, for scale. The pink arrows pointto the ends of an interesting surface. Some rocks are below this surface, and other rocks above it. What happened to make this outcrop?

The rocks below were deposited, hardened, turned on end, eroded to make an unconformity with a soil developing on top, and then other rocks were deposited on top of the soil. A is a pretty good description. The rocks below are ocean sediments, and the rocks above the soil are from a lake.

Pieces of bedrock from Canada are spread across large areas of northwestern Pennsylvania, even though the Great Lakes are between Pennsylvania and Canada. How do geologists explain this?

The rocks were carried into Pennsylvania by a glacier flowing from Canada; the base of the ice was able to flow uphill from Lake Ontario into Pennsylvania because the top of the ice sloped down toward Pennsylvania. Ice, or pancake batter, or any pile, tends to spread from where its upper surface is high to where its upper surface is low. The Great Lakes are old features, but the base of the ice really did flow up out of the Great Lakes into Pennsylvania because the top of the ice sloped down from Canada into Pennsylvania.

In the image above, a stream from the land on the right enters the ocean on the left in the lower part of the picture, and another does the same near the top of the picture. What happened where the streams met the ocean?

The sediment carried by the streams settled out in the slower-moving ocean water, forming deltas that built up as they built out so that they still slope slightly downhill toward the sea. These deltas in a fjord in Greenland are like any other deltas; the deposits cannot be purely flat-topped, or the rivers would not flow across to get to the sea water in the fjord.

Dust and shells and fish poop and all sorts of things fall to the sea bed to make sediment. Across broad central regions of the ocean, the sediment accumulates at a uniform rate—piling up about as rapidly here as it does over there. And, in most places, the currents don't move the sediment around much, so that it stays where it falls. Thus, the thickness of the sediment is related to the age of the rocks beneath the sediment. If you go around an ocean and measure the thickness of the sediment in lots of places, you are likely to find:

The sediment is thin near spreading ridges, and thicker away from the ridges. Sea floor is made at the spreading ridges, and moves away on both sides. Sediment piles up over time, and while there are variations in sedimentation rate, the huge difference in age of the sea-floor rocks (140 million years near the edges of some ocean basins, to essentially zero at the ridges) is the main controlling factor on sediment thickness. Fish actually poop wherever they travel, and tend to go all over the oceans.

Chemical reactions involve:

The sharing or trading of electrons. The clouds of electrons around the nuclei of atoms serve as the Velcro of the universe. Atoms gain or lose electrons and then stick together by static electricity, or else share electrons and stick together inside the shared cloud. The nuclei with their protons and neutrons (which are themselves composed of quarks, which also were called partons at one time) are the things held together by the electronic Velcro of chemistry.

If you could jump in a time machine and zoom back to when the Earth was only half its current age, you would probably find:

The total area of continents then was smaller than now; continents have grown over time as material scraped off downgoing slabs of subduction zones has been added to the continents. Observations show that the continents have grown, as pieces were added to the continent sides; the centers of continents are very old, and then younger rocks occur in belts around the old cores. If you kept loading the conveyor-belt at the grocery store, but there were no baggers and you refused to bag your own, you'd end up with a giant clot of groceries mashed together at the end. That is not a bad model for how continents form. If a watermelon runs into a loaf of bread, you get a big mountain-building event! Hot spots poke through continents occasionally, but don't cause much spreading so don't cause much continental growth. "Suspect terrane" is an old geologic term for rocks that drifted in on a subducting slab and then mashed up onto a continent. Geologists long "suspect"ed that these "terranes" were weird, and eventually figured out the explanation, but named them before learning the explanation. Continents can be stretched and thinned at spreading centers, and some of those spreading centers do fail and leave a stretched continent that hasn't broken to make an ocean, but more commonly

What probably happened in the above picture?

The tree started with its roots underground, but erosion washed the dirt away from them, so now they stick out. Erosion can be rapid in steep places with weak rocks, such as here on the rim of Bryce Canyon, uncovering formerly-underground tree roots. In wet places, you sometimes can observe a tree growing on an old stump, but this is a somewhat dry site with no evidence of stumps to be used for such a purpose, and the Park Service would not come in and root out a stump from under a tree. The park service promotes nature, not human sculpting of trees. This is not a Jeffrey pine, and pines in general do not grow multiple trunks. But a lot did happen here, and is still happening.

Which is younger:

The tree. The tree is growing on intrusion G, which can be shown to be younger than all of the others.

Most landslides happen when:

The unconsolidated materials on hillslopes are very wet and thus heavy and slippery, and the water doesn't have to "break" as the grains move. Dry sand can move, but even very dry times on hillsides usually don't cause landslides. But let a hurricane really saturate things, and all heck can break loose. Paving causes lots of changes, but landslides are not usually the result.

You build and maintain two biologically diverse terrariums that are identical in every way at the beginning, except that one is divided in half by an unbreachable glass wall. After some time (long enough for many generations to pass, but not long enough for much evolution to occur), it is most likely that:

The undivided terrarium will have more species than the divided one. The Pepsi Corporation is more likely to advertise at the Super Bowl. Dividing the terrarium makes two smaller populations. A species that dies out on one side cannot be replaced from the other side as in the undivided terrarium; then, loss of that species on the other side will be total loss from your terrarium.

In the bottom of Death Valley, you will find layers of gravel deposited by rivers. Based on materials presented in class, what is a likely explanation for this occurrence of river gravels in the valley bottom?

The valley was dropped relative to the mountains by faulting, and rivers now are carrying gravels down from the mountains into the valley and depositing the gravels at the valley bottom.

The ptarmigan and the marmot have something in common, other than being cute. What is it?

They both are standing on glacially eroded surfaces. The carbon-based bird, top, and the carbon-based mammal, bottom, would be unhappy if you accused him of being a silicon-based flatulent amphibians. Moraines and other glacial deposits are composed of small pieces, including till with pieces of many sizes. The striated, polished granites under these cold-climate critters were eroded by glaciers.

Scientists receive government funding primarily because:

They help humans do useful things. The government is often interested in seeing people live longer, or improving the economy, or having better and more-accurate explosive devices for the military, or in many other things that improve our lives, and science plus engineering and scientific medicine are better than any other human activity at delivering these. A cynic might say that politicians are often not all that interested in finding the Truth. And a realist would note that science is being improved all the time, and because you cannot improve on the Truth, science has not (yet?) learned the Truth. There are many methods in the world, some of them are careful, and many of them are not funded by the government. Some of our spouses or significant others may think that some scientists are sexy, but many other sexy persons are not funded by the government. One of the professors has been known to drink a competitor of Pepsi on occasion, and some scientists refrain from soft drinks entirely.

One of the big problems faced by National Parks is that:

They must allow people to enjoy things today, and preserve those things for the future, but achieving both of these is not easy. The law that established Yellowstone as the first national park required "conservation... unimpaired for...future generations" and "to provide for the enjoyment" of the parks. But what if so many people want to visit that they scare the wolves, or trample the soil and kill the roots of the big trees? Enjoying and preserving at the same time isn't easy! Fortunately, caffeinated chipmunks and maritally distressed moose are not big problems.

The things that glaciers deposit include:

Till (which is unsorted) and outwash (which is sorted). Striations, polish, cirques, hanging valleys, and rough-downglacier/rounded-upglacier (not vice versa) bedrock knobs are all features of glacier erosion, not deposition. Till, deposited directly from the ice, includes pieces of all different sizes because ice can carry all sizes without sorting by size; outwash is washed out of a glacier by meltwater and sorted by size.

Your friend wants to see some real Pennsylvania coals. Where should you send your friend to see coal in the rocks of Pennsylvania (if you honestly are being helpful), and what coals would your friend see?

To the sedimentary rocks of western Pennsylvania to see bituminous, and to the metamorphic rocks of eastern Pennsylvania to see anthracite. Bituminous is found with sedimentary rocks, but ones that have been squeezed and heated a bit so they are held together well and are not much like loose sediment; such rocks are common in western Pennsylvania. Anthracite is the most-cooked coal, and is found with metamorphic rocks in eastern Pennsylvania. Pennsylvania has lots of coal, but not much lignite, which would not be found in metamorphic rocks anyway.

John Wesley Powell, who led the first boat trip through the Grand Canyon, called the feature marked by the yellow lines "The Great _________". What did he put in the blank?

Unconformity. This is The Great Unconformity, separating inclined sedimentary rocks below from horizontal sedimentary rocks above. The rocks above are from the Paleozoic, and those below from the Precambrian. A Trompe L'Oeil painting is designed to fool the eye, but this is real.

In the picture above, Dr. Alley is discussing events that are happening outside of Grand Canyon National Park, which may impact the park. What are the issues he is discussing?

Water pumped out of the ground for golf courses and other uses evaporates, so less water flows through the ground to the springs of the canyon. Water soaks into the ground on the plateaus beside the canyon, seeps down to hit a rock layer that blocks the flow, and flows along that layer to feed beautiful and biologically important springs in the Canyon. Pumping water out of the ground on the plateaus to use for humans generally allows the water to evaporate (say, from the grass of a golf course) or run down a stream (say, below a sewage treatment plant), so the water doesn't flow through the ground to the springs.

Much melting in the mantle occurs near subducting slabs primarily because:

Water taken down subduction zones lowers the melting temperature in and near the slabs. Throw a little dry flour in a warm oven, and not much happens. Add some water, or better, some water and some carbon dioxide from yeast, and things happen in a hurry. The subduction zone takes water, and carbon dioxide in shells and other things, down to lower the melting point and feed volcanoes. Friction does warm the down-going slabs, but slabs start off way colder than the rocks into which they move, and remain colder for a while. Sliding your cold feet along the sheets when you get into bed on a winter night may warm your toes a little by friction, but if you happen to share the bed with a significant other, putting your tootsies on that persons bare belly will tell you that frictional heating takes a while! The scraped-off pile of sediment traps a tiny bit of heat, but not too much; the downgoing slab makes the nearby mantle colder than normal, not warmer. And nature tends to separate regions where something is flowing one way from regions where the flow is reversed; if the flows are too close together, one will drag the other along and change its direction. Hot spots occasionally ride along on spreading ridges, because both involve rising, but not on subduction zones.

The great scientist Alfred Wegener proposed that continents have moved, while other scientists such as T.C. Chamberlin argued against Wegener. Wegener's ideas eventually won, and are now widely accepted, because:

Wegener's ideas did a better job of predicting the results of new observations and experiments. Unlike painting or literature, scientific inquiry has a well-defined procedure for figuring out if Wegener's ideas are better or if Chamberlin had it right all along. In looking at a painting, we can ask different people what they think, or we can make up our own mind on whether we like it or not, and that is perfectly valid. In science, we have to ask: does the idea fit with the way the world works? Can I predict the results of the next observation better using Wegener's ideas or Chamberlin's? As it turns out, Chamberlin's ideas didn't predict things very well, and Wegener's did.

You are dating a lava flow by the potassium-argon system. However, the offspring in this system are leaking out of the minerals. Which is accurate?

You will think that the lava flow is younger than it really is, but you will be able to detect the error by comparing concentrations of offspring from the edges and centers of grains. Argon-40 leakage will make the lava flow appear young even if the flow is old; however, the edges of grains will lose more argon-40 than will the centers, pointing to the source of the error.

The cartoon above illustrates a specific geologic process. In which of the additional images can the same geologic process be seen?

rainbow picture *check picture The folded Appalachians, including the region of central Pennsylvania around Penn State's University Park campus, shown in the satellite image here, formed when Africa and Europe collided with the Americas, much as the two cars in the picture collided. Death Valley, Crater Lake, and George the Immense Marmot record different processes.

The cartoon above illustrates a specific geologic process. In which of the additional images can the same geologic process be seen?

*rainbow looking color photo check quiz 4 The folded Appalachians, including the region of central Pennsylvania around Penn State's University Park campus, shown in the satellite image here, formed when Africa and Europe collided with the Americas, much as the two cars in the picture collided. Death Valley, Crater Lake, and George the Immense Marmot record different processes.

First, we must calculate how rapidly limestone is being removed from the floor of the valley. Most of the limestone leaving the valley is dissolved in Spring Creek. Later, we will discuss chunks of limestone being rolled, bounced or otherwise carried out of the valley by Spring Creek, although these are rare. There is almost no loss or gain of limestone in the wind, and meteorite falls are VERY rare and can be ignored. About 1 m (just over 3 feet) of rain per year falls on Happy Valley. About two-thirds of this is used by trees and evaporated, and one-third leaves the valley in Spring Creek. That water which leaves in Spring Creek, called runoff, contains a lot of dissolved limestone, which is picked up from the ground. Spring Creek water averages about 0.33 kilograms (0.33 kg) of limestone for each cubic meter (1 m3) of water. (1 kg is 2.2 pounds, and 1 m3 is a cube just over 3 feet on a side), so the limestone in the water weighs 0.33 kg/m3. If Spring Creek collects a layer of water 0.3 m thick from all of Happy Valley each year (0.3 m3 from each square meter or m2), and each cubic meter of Spring Creek water contains 0.32 kg of limestone, then how much limestone is lost from each square meter of Happy Valley each year, on average? (Note that the units are included and calculated properly for you here, but you should understand what was done, and why.) 0.3 m3/m2/yr x 0.32 kg/m3 = __________ kg/m2/yr.

.096 Feedback: You just need to multiply 0.3 by 0.32 on your calculator. The units are there to help you understand, but you don't need them for the answer.

The answer from question 2 shows that the rock lost from each three foot by three foot plot of land in Happy Valley each year weighs a bit less than a small hamburger patty. But, how thick is the layer of rock that is lost each year? We need the density of the rock to calculate the thickness lost. The density of calcite, the main mineral in limestone, is about 2700 kilograms per cubic meter (2700 kg/m3), which is almost three tons for each three foot cube. (Rock is heavy!). There is a tiny bit of space between some of the grains in the rock, so let's use 2600 kilograms per cubic meter (2600 kg/m3) for the density. For simplicity, let's round off the answer from question 2, to obtain one-tenth of a kilogram from each square meter each year, or 0.1 kg/m2/yr (that is 0.22 pounds or 3.5 ounces, which is a bit less than the 4 ounces in a hamburger patty). Dividing this yearly rate at which each square meter of the valley is losing kilograms of rock by the density in kilograms per cubic meter yields the rate at which the valley surface is being lowered in meters per year (m/yr). The lowering rate is 0.1 kg/m2/yr divided by 2600 kg/m3 =_____________m/yr (note: your calculator probably shows a whole bunch of digits; just choose the answer below that is closest).

0.000038 (your calculator might also show this as 3.8x10-5 or something similar) You just need to divide 0.1 by 2600 on your calculator and read the answer. We know that calculator use is usually taught about third grade, so we really hope you are following the logic of this exercise as well as punching in the numbers; otherwise, it is just busy-work!

Now, imagine that instead of CO2, our cars putout horse ploppies that fell on the road. U.S. cars would be delivering the number of pounds of horse ploppies you just calculated, each year, to each square foot of paved road in the country. The CO2 from our cars, if turned to horse ploppies, would make a one-inch-thick layer spread across all the paved roads in the entire country each year. Just take a moment and think of this—what would happen if you stomped on the accelerator in an inch of recycled hay? How about braking? After a few decades, would all the roads look like pickup-truck commercials, with giant sprays of something like mud coming off the tires? Would you enjoy being a pedestrian? Would joggers switch to cross-country skiing? To get total U.S. CO2 production, you need to multiply again by about 3—we heat and air condition our homes, etc., as well as driving our cars, and most of the heating and cooling comes from fossil fuels, too. So, spread that inch of horse ploppies across your living-room carpet, and across every other living space in the nation. Put differently, the average American generates 22 tons of CO2 per year. (Compare this to a bit over half a ton per person per year of solid waste put out in garbage cans to go to landfills.) With about 5% of the world's population, we are generating about25% of the world's CO2. If you had an inch-thick layer of horse ploppies each year on every square inch of paved road in America, you very clearly would smell it everywhere—the volatile organic molecules wafting off the mess would quickly be blown around the country and the world. We don't smell the CO2, but it is everywhere, building up steadily in the atmosphere, changing the climate... and we humans clearly are influential enough to do this. So, for you alert readers playing along at home, how thick would the layer be if all the CO2 released by U.S. cars were converted to an equivalent weight of horse ploppies and spread uniformly across all the paved roads in the U.S.?(you've already seen this answer several times, actually, so for those paying attention, consider this your reward)

1 inch

The correct answer to question 4 indicates a lot of years. Could we have really screwed up the calculation so that it is way off? Well, suppose that for all of history until yesterday, Happy Valley was as wet as the wettest places on Earth. (Making central Pennsylvania that wet is almost impossible, because the wettest places on the planet have climatic characteristics that are not possible in Happy Valley. But, just suppose.) Then, the stream would have been carrying rock away faster than we calculated above. In addition, suppose that lots and lots of limestone from Happy Valley has been carried away as chunks in the stream, again meaning that rock has been removed faster than we calculated. (There is almost certainly a grain of truth to this one, but not a lot; observing Spring Creek shows that most of the rocks in transport originate in the mountains--the valley rocks mostly dissolve, and the mountain rocks wash down. But, just suppose.) Call the time to hollow out the valley, from question 4, an even 10,000,000 (10 million) years. Now, if the rock was actually removed 9 times faster than we calculated before (about as much faster as is possible with what we just told you), what would the new estimate of the time to hollow out the valley using this new, faster rate be? ________yr (your calculator may not show exactly what is listed below; if not, take the one that is closest). (If you're not sure how to proceed, ask yourself this question: if you dig faster, does it take a longer or shorter amount of time to reach the bottom?)

1,111,111 10 million divided by 9 gets you a bit over 1 million years, still a lot of years.

Total Pounds (or Tons) of CO2 Produced by U.S. Drivers per Year Calculation: Imagine for a moment that the CO2 behaved like horse ploppies, making a pile in the road, rather than wafting away in the atmosphere. How much would we have? Here are your necessary facts: There are roughly 140,000,000 cars in the country Each car averages 12,000 miles per year Each car is producing @ 1 pound of CO2 per car per mile How many pounds of CO2 are produced each year by U.S. drivers? To get this number, simply multiply the 3 variables above for this answer. This is a big number - one that cheaper calculators won't be able to handle. In this case, you'll want to come up with the number of tons instead of the number of pounds of CO2 . (2000 lbs = 1 ton). The formulas will look like this; Total Pounds of CO2 produced in a year by U.S. drivers: # of cars X # of miles per car X pounds of CO2 per mile Total Tons of CO2 produced in a year by U.S. drivers:(# of cars / 2000) X # of miles per car X pounds of CO2 per mile -- or -- Total Tons of CO2 produced in a year by U.S. drivers: # of cars X (# of miles per car / 2000) X pounds of CO2 per mile So, what do YOU come up with for this answer?

1,680,000,000,000 pounds / year (or 840,000,000 tons )

Gasoline is a remarkably interesting soup of hydrocarbons of various sorts, with bits of this and that added, but the average chemistry is not too far from being carbon and hydrogen, with two hydrogen atoms for each carbon. Burning involves combining gasoline with oxygen to make water and carbon dioxide. (Other things that are made in small quantities, such as carbon monoxide, are not as nice.) The chemical formula for burning gasoline can then be written something like: CH2+1.5 O2 --> CO2+H2O (If you don't like having one-and-a-half oxygen molecules, you can think of two hydrocarbons plus three oxygens making two carbon dioxides and two waters; it is the same thing, really.) In burning, each carbon atom, C, in gasoline eliminates two hydrogens and replaces them with two oxygens each carbon atom weighs 12 atomic mass units each hydrogen weighs 1 each oxygen weighs 16; So, CH2 starts out weighing 14 (12 from carbon and 2 from hydrogen), and CO2 ends up weighing 44 (12 from carbon and 32 from oxygen)—the weight has more than tripled. Rounding that off a little, the total weight of CO2 put out by a typical U.S. driver is three times larger than the weight of gasoline burned. To get the number of pounds of CO2 per year from a typical car, then, multiply your answer from the previous question by 3.

10,800 pounds / year

At its deepest, Happy Valley is close to 330 m (a bit over 1000 feet) deep, and it once was at least as high as the mountains around the valley. Let us call the thickness of rock removed from the valley each year, your answer in the previous blank, 0.00003 m. Then the depth of the valley, 330 m, divided by the erosion rate, 0.00003 m/yr, yields the number of years it took to hollow out Happy Valley, __________yr. This should be a large number.

11,000,000 This required punching 330, then the division key, then 0.00003, then equals. You're almost done punching buttons on the calculator. Note that 11 million years is a lot of years. If something in your mind says "That's impossible", go back and follow the logic again before going to the next question and trying to get a younger age.

And how much does that gas weigh? Hint: Your previous answer for number of gallons per year, multiplied by the weight of gas as given previously, gives you the weight of gasoline burned per year in a typical car:)

3,600 pounds / year

Pounds of CO2 per Square Foot of Road per Year Calculation:There are about 15,000 square miles of paved roads in the U.S. (the roads are long and skinny, but if you took roads and made them into a giant tennis court, you'd have about 15,000 square miles), or about 15,000 x 5280 x 5280 = 420,000,000,000 square feet (rounding off just a bit).For this answer, then, simply divide the answer from the previous question (number of pounds of CO2 per year produced by U.S. cars) by the total highway square footage number above.Cheap calculators? You likely won't be able to type in the number of square feet; in that case, if you calculated a number of tons (T) in the previous question, you should do T x 2000 / 15,000 / 5280 / 5280, giving an answer very near to:

4 pounds per square foot / year

A gallon of milk weighs eight pounds, so you wouldn't try to carry three or four gallons home on your bicycle. Gasoline is a bit less dense than milk—oil floats on water—and 6 pounds per gallon of gasoline is about right. A typical U.S. "car" (whatever it is we drive—averaging somewhere between a Prius and a Hummer, and including a lot of pickup trucks and minivans) gets about 20 miles per gallon, and drives about 12,000 miles. So, how many gallons of gas per year?

600 gallons / year

What is indicated by the yellow lines in the image above?

A great unconformity, with sedimentary rocks above resting on older sedimentary rocks below. John Wesley Powell, of the United States Geological Survey, and the leader of the first boat trip through the Grand Canyon, called the feature marked by the yellow lines "The Great Unconformity". It separates horizontal Paleozoic sedimentary rocks, above, from inclined Precambrian sedimentary rocks, below.

The picture above shows: *check pciture

A right-side-up dinosaur track. This is a dinosaur track, from dinosaur ridge, and the dinosaur stomped down into the mud, so the track is right-side-up.

An unconformity is:

A time gap in a sequence of sedimentary rocks caused by a period of erosion or nondeposition. Most of the land is eroding most of the time. Streams carry rocks and mud away from the mountains, lowering the mountains. Eventually, if mountains are lowered enough, by erosion or by Death-Valley-type faulting or some other process, new sediments may be deposited on top, but there will be a surface separating older rocks from younger rocks, and no rocks from the in-between time. This surface is called an unconformity. One can see older clasts in younger rocks, but these are usually called "older clasts in younger rocks", not unconformities. Whatever events made the old rocks, broke them up, and transported them to the site where the new rock formed must have happened before the new rock formed. A rock must exist before it can be cut, so an igneous rock cutting a sedimentary rock is younger than the sedimentary rock, and geologists do study such cross-cutting relationships, but they aren't unconformities. Younger sedimentary rocks do occur on top of older rocks unless turned upside-down by mountain building, but this goes by the fancy name of the "principle of superposition", not "unconformity". And younger fossils looking more like living things than do older fossils is William Smith's "law" of faunal succession, not an unconformity.

Dr. Alley is pointing to a brownish zone exposed in the low bluff along Coast Guard Beach, Cape Cod National Seashore. The brown zone is rounded on the bottom, flat on the top, rests on sand and gravel, and has sand dunes on top. In the lower picture, Dr. Alley is showing that the brown zone contains twigs and other organic material. What is the brown zone doing here?

An ice block from the glacier was buried in sand and gravel, then melted to make a lake that filled with organic material. Cape Cod is a creature of the glaciers, and most of the Cape's lakes started by melting of buried ice blocks. Sinkholes and human-made lakes do fill with organic material sometimes, but this is the wrong setting. A whale carcass wouldn't be twigs, etc. In Oregon, the highway department did once try dynamiting a whale carcass to speed natural decay, and succeeded in splattering bystanders and even denting some car roofs with large flying whale parts. (One has to wonder whether there exists a rock band somewhere named "Large Flying Whale Parts".)

National Parks are:

An invention of the United States that has spread around much of the world, as a way of protecting some of the finest parts of the world. Yellowstone was the first National Park, but now you can find National Parks scattered across the planet, preserving key areas for the enjoyment of this generation and for future generations.

The picture above shows a beautiful specimen of Araucarioxylon arizonicum, a fossil tree from the Mesozoic rocks of Petrified Forest National Park. Based on the discussions of evolution in the class materials, it is likely that:

Araucarioxylon arizonicum is related to, but recognizably different from, trees still alive today. Evolutionary theory indicates that living things change from generation to generation, but that all living things are related. Consistent with this, Araucarioxylon arizonicum is recognizably similar to, yet different from, Araucaria trees such as monkey puzzle that are native to southern South America today.

When geologists consider sedimentary rocks, those rocks:

Are classified first based on origin (clastic or chemical precipitate). We do divide the rocks based on origin first. We saw with weathering that physical weathering makes chunks or clasts, and then chemical weathering also makes chunks (clay, rust, sand grains) and dissolved things. The clasts give clastic rocks, and when the dissolved things come out of solution, chemical precipitates are formed. Color is not often a useful indicator—rock colors change a lot during weathering, and colors also may change when oil or water move through. Grain size matters to clastics, but not much to precipitates.

The volcanoes on the island of Hawaii (and the Loihi seamount, a submerged volcano to the southwest of Hawaii):

Are not located at a subduction zone or other plate boundary, but instead poke through a plate drifting over the Hawaiian hotspot. Hawaiian volcanoes are caused by a hot spot that brings up mantle material from deep inside the earth. Hot spots can occur anywhere, not just at plate boundaries. The volcanoes of Hawaii are made up of high-viscosity basaltic rocks that spread out over large distances, making broad, gently-sloping volcanic mountains. These volcanoes don't erupt explosively because the rocks tend not to trap gasses effectively.

Using ordinary means (fire, sunlight, our digestive systems) we can take matter apart into smaller and smaller pieces, and the smallest pieces we typically produce are:

Atoms.

Look back at pictures 2 and 1. These are close to each other. 1 is fairly new paving on a road, and 2 is a somewhat older bicycle trail. An hypothesis that is reasonably motivated by these observations, and by the other blacktop pictures from the previous question, is:

Bicyclists aren't as heavy as cars, and the extra stress from heavier things tends to crack blacktop. You can break a brand new coffee mug by hitting it with a hammer. Damage tends to accumulate with time, but extra stress also causes damage to accumulate. The bicycle trail is not stressed as much as the road because bicycles are lighter than cars and trucks, so the blacktop on the bicycle trail can last longer than the blacktop on the road.

The diagram above shows a geologic cross-section of some rocks, such as you might see in a cliff. The tree is growing on top of the modern surface. Rock layers A, B, C, D, E, and F are sedimentary; E contains mud cracks and fossil footprints as shown. G is igneous rock that hardened from hot, melted rock. H, I and J are faults, and K and L are unconformities. Sedimentary rocks are right-side-up unless there is some indication given to show something else. Referring to the rocks you see here ......Which is the oldest sedimentary rock layer?

C *CHECK PICTURE The package of sediments C, D, E, and F is upside-down, as shown by the footprints and mud cracks, so C is the oldest one.

You are still a geologist, still wandering around in a fog with a tea-and-crumpets-toting student, and you walk into another cliff. This one turns out to be a hardened lava flow. Again, you look at a one-foot-square region, sketch pink arrows with A, B, C, and D on that region, and ask the student which of the pink arrows was pointing up just after the lava flow hardened. To help the student, you draw four additional arrows on the cliff; these are light blue (turquoise) arrows, pointing at bubbles. (If you are not able to distinguish pink from light blue, the four pink arrows are very close to the four letters A, B, C, and D, and the four light-blue arrows are not close to the letters.) You suggest that the student consider the behavior of bubbles in a liquid. These bubbles are within the lava flow, and not in the crust on top of the flow that was chilled very rapidly by the air. Your student is brilliant, and correctly tells you the answer. The pink arrow (close to a letter) that was pointing up when the lava flowed in and slowly cooled is the arrow that is closest to:

C Pointing Down Below the frozen upper crust of a lava flow, bubbles tend to rise, and they tend to grow as they rise because less pressure squeezes them near the top of the flow, and because they pick up dissolved gas from the flow as they rise. So, you expect a big-bubble layer near the top and a little-bubble or even no-bubble zone near the bottom. Two of the blue arrows point to big bubbles on the "C" side, and two point to little bubbles on the "A" side, so you know that C must have been the top when the lava flow was cooling.

As described in the introduction to this exercise, citations are very important in the scientific literature. They show where ideas or techniques came from, who has done similar work, and more. The Web of Science used to be called the Science Citation Index, and started out keeping track of citations in scientific papers. This allows you to work forward and back. For example, search on Anandakrishnan S, and find the paper from 2006 first-authored by graduate-student L.E. Peters, and published in Journal of Geophysical Research—Solid Earth. This is an important paper linking geology and ice behavior in the West Antarctic ice sheet. If you click on the blue title of the paper, you will see "Times Cited:" in black, followed by a number in blue (that number increases over time), and "References: 75" with "75" in blue. Clicking on the blue "75" will tell you all of the papers that Leo Peters relied on in preparing his paper. Clicking on the blue number after "Times Cited" will tell you all of the papers who have cited Leo Peter's paper, and thus are relying on it. Click on the "Times Cited" number. Fellow graduate student A.P. Rathbun cited the Leo Peter's paper in 2008. Who was the second author on Andy Rathbun's paper? Note: The world is not perfect, and sometimes an entry will end up slightly out of order compared to what you're expecting. In particular, these are ordered based on the time they reach the indexing service, not based on the publication date. So if at first you don't see what you're looking for, scan up and down a bit.

C. Marone C. Marone is a popular and successful Penn State professor, and world-class researcher. The easiest way to have missed this question is by clicking on the wrong paper by Peters and Anandakrishnan; these authors worked together on a few projects, but only one of those was in 2006 in Journal of Geophysical Research-Solid Earth.

Tsunamis:

Can be predicted with some accuracy seconds to hours before the waves strike in most cases, allowing quick warnings to save many lives. Because tsunamis are triggered by earthquakes, among other things, and we cannot predict earthquakes accurately, we cannot make months-in-advance predictions of tsunamis. The p-waves from the earthquakes that cause the most common tsunamis move more rapidly than the tsunamis do, allowing timely warnings; however, because the tsunamis get where they are going in hours or less typically, not much time is available. Water does go out before rushing in along some coasts, but comes in before going out along other coasts, waves have "up" and "down" parts, and some coasts get an "up" first while other coasts get a "down" first. Little earthquakes make little tsunamis; big earthquakes make big tsunamis.

During the most recent ice age:

Central Pennsylvania was just beyond the edge of the Canadian ice. This is just a fact of geography as described in the text; central Pennsylvania was near but beyond the edge of ice coming from the north. The last option, "no one knows", is the last refuge of lazy minds, and not at all correct.

What cause probably was not important in contributing to extinction of most species on Earth, including the dinosaurs, in a very short interval of time at the end of the Mesozoic Era?

Cold from the change in Earth's orbit caused when the meteorite shoved the planet farther from the sun. Robert Frost once wrote "Some say the world will end in fire, some say in ice". For the dinosaurs, both were probably true, with acid thrown in. But the meteorite was not nearly big enough to change the planet's orbit noticeably. Frost went on "From what I've tasted of desire, I hold with those who favor fire, But if it had to perish twice, I think that for destruction ice, Is also great, and would suffice."

Considering long-term averages, and assuming that we don't deploy space-based defenses against incoming meteorites, a reasonable estimate of the chance of an average U.S. citizen being killed by the effects of a meteorite or comet impact is that this risk is about the same as the chance of being killed by:

Crash of a commercial airplane. Nobody that we know eats Pepsi cans, and while there are still meteorites in the solar system that can hit and kill, there are no dinosaurs left except on "The Flintstones". A reputable study found that a meteorite impact might not occur for millions of years (or might occur next year...) but then might kill billions of people; plane crashes usually kill a few to a few hundred each year. Add up the deaths over a sufficiently long time, and plane crashes and meteorite impacts likely are similarly dangerous. But car crashes, smoking, and being fat and lazy are way more dangerous to us.

You are a geologist. While walking in the fog one day, you bang into a cliff. After rubbing your sore nose, you inspect the cliff, and see what is shown in the picture, in a one-foot-square area. You recognize that this cliff is made of "fossil sand dunes", with wind-blown sand that was later glued together by hard-water deposits. You are accompanied by a student, who is carrying your tea and crumpets for you. You sketch four arrows on the cliff, label them as shown, and ask the student which of the arrows was pointing up when the loose sand was deposited. Your student is brilliant, and correctly tells you the answer. The arrow that was pointing up when the loose sand was deposited is the arrow that is closest to:

D - Pointing West Several small sand dunes are visible in this picture. Originally, the whole picture was rotated so the D was up and the B down. The first deposit was made by wind blowing from the C to the A, putting down slightly slanting layers in the lee of a dune; these layers are behind the B now. Then, the wind eroded away the top of the dune, cutting the layers, and then new sand was deposited on top of the cut ends of the layers. The cut ends must be up, where the wind could reach them, which tells you that the D side was originally up.

Compare pictures 1, 4, and 5. These three pieces of blacktop road are within a mile of each other and have experienced similar traffic (except that after 5 fell apart, people quit driving on it). A really good hypothesis based on these is that:

Damage accumulates with time, so that older blacktop is more broken up. The recently laid blacktop looks pretty good, and the blacktop that was put down the longest time ago is barely recognizable as blacktop. You should not be surprised to learn that damage tends to accumulate with time as the blacktop breaks up.

There are numerous clues in these pictures to how rapidly loose material can roll, slide, or otherwise move downhill, and the conditions needed for such motion. Some interesting things you can learn include:

Downhill motions can be slow (years or decades or longer) or fast (days or less). Most soil motion is fairly slow, maybe an inch a year or so, and grass or trees tend to hold the soil and slow the motion. But, sometimes a giant landslide sweeps things away in seconds, or a groundhog moves more dirt in an afternoon than the slow creep would have moved in a year. Really understanding how the surface changes requires thinking about many processes operating at many speeds.

The picture shows some rocks on the beach at Olympic National Park. The pocket knife is about 3 inches (or 8 cm) long. What is the story of these rocks?

Earthquakes knocked loose undersea muds that raced down the slope into the subduction zone to make these layered rocks, which were scraped off the downgoing slab, part of the process by which continents grow as material is added to their edges at subduction zones. Olympic is the pile of scraped-off stuff, and some of it fell into the trench rather recently during earthquakes. Build-up of material above subduction zones contributes to growth of continents over time, not shrinkage. There really are volcanic layers, but as described in the slide show, these are not volcanic layers, and continents grow over time rather than shrinking. Things do wash off freighters, and items such as rubber ducks and shoes have been used to trace ocean currents, but pocket knives sink, and ocean currents are not the driving force for drifting plates. Airline toilets flush into holding tanks on the plane, not onto people or rocks below, and very rarely have pocket knives because the knives are confiscated first.

Now consider the following statement: "At least we don't need to worry about weather and landslides and downhill motion and all of those things attacking buildings, because natural processes don't bother buildings.

False Nature attacks buildings, just as nature attacks pavement. Some of your rent (if you rent), and some of your tuition (if you pay it), are used to patch buildings, but the wear shows anyway.

A scientist sees a crack near a tree. A scientist, doing real science, will assume that the tree caused the crack, call it science, and move on.

False Science is really people trying to understand the world by working really hard, following their curiosity, but agreeing to follow a set of rules that make it very hard for them to fool themselves and others. The idea that the tree roots crack the sidewalk is a starting point for science, not an ending point.

Databases are available through the Penn State Online Library System (Links to an external site.) (http://www.libraries.psu.edu/psul/home.html). Our favorite is Web of Science (obtain by clicking on "Databases" which you will find in the "FIND" box on the Libraries homepage). Type "Web of Science" into the search box and select "Web of Science from the resulting page. (There may be a delay as the website loads.)

For the Following Question 2:6

In the picture above, the ice that modified the rock moved:

From left to right, striating the surfaces the ice reached first and plucking blocks loose from the far sides of bumps. Indeed, ice sandpapers and striates the rocks it hits first, and then plucks blocks loose from the other side. And the striae go in the direction that the ice moved.

A glacier almost always flows:

From where the glacier's upper surface is high to where the glacier's upper surface is low. The great ice sheet of Greenland spreads from its central dome, so the ice on the south side is moving south, the ice on the north side is moving north, the east-side ice moves east and the west-side ice moves west. Ice flows down many mountains, such as Mount Rainier, but ice came across the Great Lakes and up into the US. Thus, ice flows from where its upper surface is high to where its upper surface is low.

As water from rain soaks through the soil, the water typically:

Gains carbon dioxide (CO2) from the air and then gains more carbon dioxide in the soil, becoming more acidic. CO2 is fairly soluble in water. Rain picks up some in the air, becoming slightly acidic. Lots of things living in the soil emit carbon dioxide, and soils contain a lot of carbon dioxide that helps make water more acidic. Humic compounds are picked up from soil by water, and make the water more acidic.

The glacier shown above: *CHECK PICTURE

Has retreated, because a decrease in snowfall to the accumulation zone (A) or an increase in melting of the ablation zone (B) occurred. Accumulation is a building up, ablation a wearing away or loss. The glacier builds at high elevation (A) and wears away at low elevation (B). And, the halo of moraine around this glacier at low elevation shows that the ice has retreated, so a decrease in snowfall to the accumulation zone or an increase in melting of the ablation zone is indicated.

Volcanoes in Death Valley:

Have erupted recently (within the last centuries or millennia), showing that hot rock occurs at shallow depth beneath the valley. Death Valley, and many of the surrounding parts of Nevada and California, have experienced geologically recent volcanic activity. This is one of the problems facing the plan to put nuclear waste in an underground repository in Nevada and leave that waste—are we sure that a volcano won't erupt through the repository? There has not been enough lava erupted to fill the valley, however, nor do volcanoes erupt Diet Pepsi (although you can make a nice volcano model by quickly popping the top of a hot, shaken can of pop).

Which of the following is not part of the evidence that the odd layer marking the extinction of the dinosaurs was caused by a large meteorite impact?

High concentrations of silica found in the layer. We have seen several times that silica is very common, so its presence in a layer would not indicate much of anything. Features really observed in the layer that are associated with meteorites but not common elsewhere in rocks include shocked quartz from the impact, soot from wildfires, iridium from the meteorite, and a giant-wave deposit because the meteorite hit water as well as land at the edge of the Yucatan Peninsula.

If you watched a sand grain moved by waves on a beach on the U.S. east coast, you would usually see that most of its motion:

Is alternately toward and away from the shore, causing little net change. A beach sand grain spends most of its time coming in, going out, coming in, going out, and not getting anywhere. A tiny bias exists, such that the in and out will move slightly along the coast, and will cause seasonal changes.

Using only uniformitarian calculations from the thickness of known sedimentary rocks, likely rates at which those rocks accumulated, and features in and under those sedimentary rocks, geologists working two to three hundred years ago estimated that the Earth:

Is more than about one-hundred-million years old. Radiometric techniques reveal the Earth to be about 4.6 billion years old, but early geologists did not have the sophisticated instruments to measure the trace radioactive elements and their offspring. Working from the rocks, the geologists knew that the age must be in the neighborhood of 100 million years, plus extra time in unconformities and additional extra time in the oldest, metamorphic rocks.

Calcium released by chemical weathering is transported by streams to the ocean, where much of it:

Is used by clams, corals, etc. to make their shells Most common shells seen at the beach are calcium carbonate, and the calcium is provided by weathering of rocks on land. Calcium ions do not evaporate easily, and are not very common in the atmosphere. A little bit of sea salt, and anything else small in the sea, does escape in spray (stand by the sea on a windy day and you'll get spots on your sunglasses), but most of the calcium reaching the sea is used there. The "saltiness" of the ocean is a quite different chemical, not calcium. Some shells are subducted, many more are scraped off downgoing slabs at subduction zones, but subduction does not occur at mid-ocean ridges, which is where sea floor is made, not where sea floor is consumed. Calcium in milk is a good thing, and helps build strong bones and teeth, but dairy cows rarely go to the beach to go swimming, and wouldn't enjoy drinking the water to get their calcium. There is a little bit of calcium in grasses, and cows get some of their calcium from there.

The above picture is from the Escalante-Grand Staircase National Monument. The pink arrows point along some interesting features. What are they?

Joints, formed when the sedimentary rocks were broken by physical-weathering or other processes. This is the Navajo Sandstone, and it is a sand-dune deposit, but you can't really see that in this picture. Almost all rocks have joints. Joints channel water, and make space for roots, so plants often grow along joints, as you see here. The change from red to white along the upper-left arrow is probably a record of places in the past where fluids carrying oil met fluids carrying water—the water rusted the iron and made red; the oil left the iron reduced and carried it away.

What sort of rock is the dark material very close to the pink granite that Dr. Alley is pointing to in the picture above? *check picture quiz 4

Metamorphic; The rock separated into layers as it was cooked and squeezed deep in a mountain range. The large crystals, intergrown nature, and separate dark and light layers all point to metamorphism, deep inside a mountain range. Rapid cooling in volcanic eruptions gives tiny crystals, not the big, pretty ones here. You can see the former sand grains or other-sized pieces in sediment and sedimentary rocks. And marmot doo-doo consists of small, dark pellets, akin to big rabbit doots, and usually isn't considered to be rock.

Major differences between Mt. St. Helens and Hawaiian volcanoes include:

Mt. St. Helens is a medium-to-high-silica, explosively erupting stratovolcano, and Hawaii has low-silica, quietly erupting shield volcanoes. The low-silica lava from the Hawaiian hot spot flows easily without large explosions, so the lava spreads out to make broad, gentle volcanoes that look like shields of medieval warriors. Melt a little basaltic sea floor with some water and sediment, and you get silica-rich andesite feeding explosive, subduction-zone stratovolcanoes such as Mt. St. Helens. Hot spots and spreading ridges make low-silica, basaltic volcanoes, which don't explode powerfully. Mt. St. Helens is a stratovolcano, but stratovolcanoes are steep, not broad and flat. Mt. St. Helens was the most active of the Cascades volcanoes even before its big 1980 eruption, and the volcano has erupted many times since the big eruption.

Geological evidence based on several radiometric techniques has provided a scientifically well-accepted age for the Earth. Represent that age of the Earth as the 100-yard length of a football field, and any time interval can be represented as some distance on the field. (So something that lasted one-tenth of the age of the Earth would be ten yards, and something that lasted one-half of the age of the Earth would be fifty yards.) On this scale, how long have you personally been alive?

Much less than the thickness of a sheet of paper. If the 4.6 billion years of Earth history are 100 yards, then the few thousand years of written history are just one-millionth of that history, just over the thickness of a sheet of paper. And your small piece of written history must be only a small fraction of a sheet of paper, roughly 1/200th or so.

The final arbitrator between two alternate theories (for example Aristotle's and Newton's ideas) is:

Nature, and experiments conducted to test each idea.

There may be more than one S. Anandakrishnan, or R.B. Alley, in the world. One way to tell them apart is to check the address, which is also listed in the Web of Science. The Web of Science actually tries to help you. If you make sure to click the tab near the upper left that says "Web of Science" rather than "All Databases" before you do the search, it provides a "View Distinct Author Sets" option. In this case, don't mess with that. In the Web of Science, just search on Anandakrishnan S, and find the paper by Balasubramanian and others from 2004. Is this the same S. Anandakrishnan from Penn State's Geosc10 that you know as Dr. A? (If you find a Penn State address in the list below, you may assume that it is the same Dr. A you know, and if you don't find a Penn State address, you may assume that the author is a different S. Anandakrishnan; we won't make you click through other Dr. A references to make sure)

No There really are many people in the world named John Smith, and there really is more than one S. Anandakrishnan in science. The S. Anandakrishnan studying tuberculosis in India is not the S. Anandakrishnan studying polar ice sheets from his base in Pennsylvania.

As discussed in the introduction, refereed sources are very important in science. Refereed sources often are identified by names such as Journal of... or Annals of... or Transactions of.... They usually have a statement somewhere in the journal describing their standards for review and publication. A paper in a refereed journal usually starts with an abstract and ends with a list of references cited, and usually with an acknowledgement of funding sources and other sources of help. In between, there usually are sections such as Introduction, Methods, and Discussion/Conclusion (different papers have somewhat different sections). Refereed journals usually do not have advertising, although a few do, so don't rely on this one—look for the title, the abstract, the references, etc. Two journals that occasionally cause trouble are Nature and Science—both start with newsy, non-refereed parts with advertising, but this is followed by refereed scientific parts without advertising but with abstracts, references and acknowledgements of funding sources. Time and Newsweek are not refereed scientific journals (Dr. Alley once had an interesting exchange with a US Senator, who initially insisted that Newsweek speaks for the scientists of the world, but changed his stance when shown that Newsweek was contradicting the National Academy of Sciences.) National Geographic, Natural History, American Scientist and Scientific American are not refereed and are not acceptable--they are interested in whether something is newsworthy and can be reported legally, not necessarily whether it is true. If an important person says something stupid, it may be newsworthy and appear in Newsweek, even if the statement is not correct and would not appear in a refereed scientific journal. (The Web of Science actually includes Scientific American and American Scientist, because the Web figures that their users know the difference.)About Web Sites: Some scientific journals are now on the Web, so some Web sites (a VERY small percentage of the total) are now refereed and part of the scientific literature, but almost all Web sites are not. Wikipedia may be a nice shortcut to learn a lot of things, but it is NOT refereed in the ordinary sense; it (like this textbook) is no better than a secondary source. As a general observation, much of what is published in books is fiction, including much of what is published in supposedly non-fiction books. Books are typically not reviewed and so are not as reliable as the scientific literature. Because publication of a book is expensive, some quality control is used by publishers, although typically not enough. Because Web sites are so incredibly cheap, they experience much less quality control and all should be suspected of propagating nonsense. The Web is a great way to transmit words, pictures, and numbers, but much or even most of the transmitted material is misleading or wrong. Be wary of all Web sites! Make them prove reliability to you before you believe them. Click on the link to download the two articles. Which one is refereed?

Paper #1, "North American continental margin records of the Paleocene-Eocene thermal maximum" You could follow our description—Paper 1 has an abstract, an introduction and a boring title, and paper 2 doesn't. Or, you could note that paper 2 is from Scientific American, and we told you explicitly in the instructions that Scientific American is not refereed.

Look at the picture above, which shows a small section of a "fossil" sand dune (a sand dune in which the grains have been "glued" together by hard-water deposits). When the dune was first deposited, which was up (which letter is closest to the arrow that is pointing in the direction you would have looked to see the sky when the dune was deposited)?

Picture of dark spot *check picture B Just to the left of the letter �B� there is a small unconformity. The layers farther to the left are cut along that surface. Layers must exist to be cut, so the left-hand layers are older, the right-hand layers are younger, and �up� was to the right.

What tectonic setting is primarily responsible for producing Mt. St Helens?

Push-together Subduction Mt. St. Helens sits above a subduction zone, where one tectonic plate goes below another as they come together.

In age dating, geologists use:

Radiometric techniques and layer-counting for absolute dating of events that happened in the last 100,000 years, and other radiometric techniques for absolute dating of much older events. If you want an absolute date (number of years) rather than older/younger, you can count layers for young things, or use radiometric techniques for young things or for old ones.

Dr. Alley took this picture in central Utah. The rock shown started out as soft sediment deposited in Lake Flagstaff, at about the same time and just a little north of the lake in which the limestones of Bryce were deposited. These lakes grew and shrank with changing climate, often forming muddy flats that dried and cracked to make mud cracks, which then were filled and covered by more sediment as the lake grew again. The pocket knife shows you that this sample is a foot or two in length. The sun was high and hot when the picture was taken, but slanting in from the left as shown, and we have provided arrows to direct your eye to a couple of shadows. Dr. Alley placed this sample so it could be photographed easily. Did he place it upside-down (you are looking at the side that was down when the sediment was soft) or right-side up (you are looking at the side that was up when the sediment was soft)?

Right-Side up *check picture Mud cracks extend downward into soft sediment. When more sediment is washed in, this second layer will fill the cracks beneath. Later, after the layers have hardened, the rock may be cracked apart. If you see troughs in a mud-crack pattern, you are looking at the side of the second layer that originally was up. You can tell that this picture shows troughs, and not ridges, by the shadows—troughs have the light and the shadow on the same side, as shown here, whereas ridges have light and shadow on opposite sides.

The picture above shows a muddy limestone that was deposited in shallow water of a lake. The pocket knife is sitting on a high region of the rock. The pink arrow points along a low trough or groove in the rock, and several other such grooves are evident. The rock is:

Right-side-up; you are looking at the side that was facing up toward the sky when the rock was deposited. These are mud cracks, and they go down into the mud, so the rock is right-side up.

Based on what you have seen and read:

Rocks are changed physically, but also chemically, and the chemical processes may prove to be diverse and complex, involving rusting, dissolving in rainwater, actions by lichens, and perhaps others. A gravestone doesn't need to stand up to one physical or chemical process, but many physical and chemical processes. Chemically, rain is naturally slightly acidic, our coal-fired power plants increase the acidity, lichens make their own acids, and acid attacks rock, while oxygen and water rust the iron in some minerals, and much more. In the words of Dr. Suess, "There I was all completely surrounded by trouble..."

You drill through the muds at the bottom of the sea floor and sample the rocks beneath, and you then determine the ages of those rocks, using standard scientific techniques. As described in the course materials, you will find that:

Rocks farthest from spreading ridges are oldest, with ages decreasing as you move toward a ridge. At sea-floor spreading ridges, hot magma rises up, cools and solidifies. These rocks then split and move apart as yet more magma rises, cools and solidifies. Over time, the rocks are moved great distances (tens or hundreds of miles) from the spreading ridges. The rocks close to the ridges were deposited recently (they are "young"), but the rocks far from the ridge were deposited long ago and then moved away slowly (they are "old").

Scientists collaborate a lot. The Web of Science tells you who all the coauthors are. Search on Dr. A (Type "Anandakrishnan S" into the author box of the search page). Notice that many of the entries list a few authors followed by "et al." (which stands for "et alia" and means "and others" in Latin). If you click on the blue title, you'll see a list of all of the authors. So, who was Dr. A co-authoring with in 1997?

S.R. Taylor and B.W. Stump, among others. Dr. Anandakrishnan collaborated and coauthored with all of the people listed, and has worked with many other people; the key is finding the 1997 list. Dr. Anandakrishnan's 1997 colleagues worked at Los Alamos laboratory when he was there, addressing the key question of identifying illegal atomic-bomb testing by rogue nations. Blasting in surface coal mines can involve huge explosions, and Dr. Anandakrishnan helped show how to distinguish between these legal explosions and illegal ones.

The picture shows hard stone that was once soft sediment, from the Tonto National Monument, Arizona. Examination of the sample tells a geologist that mud cracking was occurring where the sample formed. When the picture of this sample was taken, the light was shining along the arrow, as shown, making shadows, some of which are indicated by the arrows. Are you looking at the side that was down when the sediment was soft, or the side that was up?

Side that was down *check picture Mud cracks extend downward into soft sediment. When more sediment is washed in, this second layer will fill the cracks beneath. Later, after the layers have hardened, the rock may be turned upside-down and then the layers cracked apart (or, the layers cracked apart and then turned upside-down). If you see ridges in a mud-crack pattern, you are looking at the side of the second layer that originally was down. You can tell that this picture shows ridges, and not holes, by the shadowsridges have a light on one side and a shadow on the other, as seen here, whereas holes have light and shadow on the same side.

Dinosaurs once stomped across much of the planet, sometimes leaving tracks in mud that were buried in more mud and later hardened to stone. This sample is from the Philmont Scout Ranch in New Mexico. It is a loose block that fell down from a cliff above. The footprint was made by a Tyrannosaurus rex. The print is 33 inches long (almost 3 feet for one foot!) and 28 inches wide, and extended 9 inches deep into the sediment. The sun was shining as indicated, and the black arrows point to shadows from two of the three toes of the track. Are you looking at the side that was down when the sediment was soft, or the side that was up?

Side that was down *check picture Footprints are pushed downward into soft sediment. When more sediment is washed in, this second layer will fill the print beneath. Later, after the layers have hardened, the rock may be turned upside-down and then the layers cracked apart (or, the layers cracked apart and then turned upside-down). If you see a footprint sticking up, you are looking at the side of the second layer that originally was down. You can tell that this picture shows a track sticking up by the shadows—ridges or other things that stick up have a light on one side and a shadow on the other, as seen here, whereas holes or troughs or other things going down have light and shadow on the same side. According to the United States Geological Survey, the T. rex responsible for this track was probably moving 6 or 7 miles per hour. A mature T. rex would have been about 60 feet long, two stories high, and 10,000 pounds or so, quite capable of making a 33-inch-long, 9-inch-deep track in mud.

Glaciers form where:

Snowfall exceeds melting for a long enough time. Anyone from Erie can tell you that a snowy winter does not guarantee a glacier, and anyone from the permafrost of Siberia could add that cold does not guarantee a glacier. Many high mountains are free of ice, and some warm places are being raised tectonically. The way to make a glacier is to pile up more snow than melts.

In the Great Smokies:

Some older rocks were shoved on top of younger ones by push-together thrust faulting. Both folding and thrust-faulting occurred in the Smokies, with some rocks turned on edge or turned over, and some older rocks shoved on top of younger ones. Slide-past faulting was minor, as was marmot #2.

What causes the great majority of earthquakes?

Stick-slip behavior across faults There may be "implosion" earthquakes, but they are rare. Some breaks in the crust are well-lubricated and don't make earthquakes. If rocks on opposite sides of a break move in the same direction at the same speed, then there will be no relative motion between those rocks, and they won't make earthquakes. But when rocks try to move in opposite directions but are stuck, they bend like springs and then break, shaking things and knocking them down in an earthquake. And Diet Coke drinkers who have not yet had their caffeine are unlikely to be sufficiently agitated to kick the Pepsi machines hard enough to make the larger earthquakes that are observed.

What is more accurate about the Earth?

The Earth is formed of concentric layers (something like an onion--a central ball with a shell around it, and a shell around that...); when the planet melted, it separated into layers. The planet is onion-like, with an inner core, then an outer core, a mantle (which has several sub-layers), and a crust. The moon-making collision did happen, but the planet got hot enough to separate again. The planet separated after melting largely or completely, with the densest stuff falling to the center and the lowest-density stuff floating to the top.

After looking at the images above and reading their captions, take a look at this cartoon drawing of a gravestone. The big "F" is in the middle of the face of the gravestone, and the big "C" points right to a corner of the gravestone. The pictures show that the "C" is more likely to be knocked off than the "F". Why?

The F can be hit only from the front but the C can be hit from more sides, and the F has more rock around it holding it in than the C does, both of which make the F harder to break than the C. Neighbors are useful in lots of ways. They can protect you from sneak attacks coming from behind or beside you, and hold you up in case you start to fall. Lose the guard and the support, and you're more vulnerable. The same is true for erosion—something sticking out on a corner is more likely to get hit and less strongly held in place, and so is much more likely to break off.

Based on the appearance of the numbers and the corresponding text in the first six pictures, it is mBased on the appearance of the numbers and the corresponding text in the first six pictures, it is most likely that:ost likely that:

The different stones wear away at different rates, with granite most resistant and marble least resistant. Time and stress matter, but so does composition. People behave differently at different ages in their lives, and may change behavior as the stress level changes, but what you're really made of does show through in the tough spots. For rocks, granite stands up to the weather better than marble does in a Pennsylvania graveyard.

In question 4, you estimated the time for lowering the surface of Happy Valley enough to account for the modern difference in elevation between the top of Mount Nittany and the bottom of the valley. In question 5, you saw that you could change that estimate a good bit. But, to make a 10-fold change in the estimate, you had to assume things that are really almost impossible, such as making central Pennsylvania one of the wettest places on Earth. We could tweak the assumptions in the calculation to move the estimate either way by a few-fold (so 10 million years could become 3 million years, or 30 million years, without too much trouble), but shifting the answer a whole lot further than that requires impossibilities or miracles--just because we can shift it to 3 million years or even 1 million years does not mean we can shift it to 10,000 years, which would require digging the valley 1,000 times faster than is happening now, which nature really cannot do here. We can say something else important, though. Whatever the time needed for deepening the valley, the geologic story of central Pennsylvania must be much longer than that-- time-deepening the valley is only the last act of a long play. The text of this exercise refers to several reasons why we know that the story is longer than the deepening of the valley. Which two statements below describe something indicating that the region is much older than calculated so far in this exercise?The geology of the region shows that the modern valley once had a mountain on top of it, so erosion had to take the mountain off before digging the valley, thus requiring a longer time.

The geology of the region shows that the modern valley once had a mountain on top of it, so erosion had to take the mountain off before digging the valley, thus requiring a longer time. The rocks needed to be deposited, hardened, and bent before being eroded, and all of that took time.

Air that passes over the Sierra Nevada from the Redwoods to Death Valley is warmed by roughly 30oF, even if the air goes over at night. Where does the energy come from?

The heat that had been stored during evaporation from the ocean and was released when clouds formed on the west side of the Sierra Much of the sun's energy that falls on the tropics is stored by evaporating water, and only later made so you can feel it (called sensible heat) when condensation reverses the evaporation. If the warming happens at night, then direct warming from the sun cannot be correct. The Sierra is no longer volcanically active, and volcanoes rarely emit enough heat in a broad enough zone to affect general winds much. The Earth does rotate, and this does cause winds to curve as they blow over the surface, but that curving doesn't add heat to the system. And while marmots do produce a little methane, and a bit of heat, they don't produce nearly enough to matter to the climate.

The pictures show evidence of where mud has moved, or hasn't moved. The pictures also tell you something about when mud moves—Dr. Alley took the pictures when it wasn't raining, and while he was taking them he did not get his bike tires buried by mud. A reasonable interpretation is:

The mud moves mostly when it is raining, and the bare parts of the landscape that are not paved contribute most of the moving mud. Trees and grass slow the downhill creeping of dirt, and really slow the downhill washing of dirt. A very small bare spot may supply more mud in a rainstorm than a big grassy area—construction sites do make nearby streams muddy during rainy times unless care is taken to trap the mud. Most of the mud moves in short intervals, especially during really heavy rains.

In chemistry, the type of an atom (what element it is) is determined by:

The number of protons it contains in its nucleus. Physicists change the name when the number of charged, massive protons in the nucleus changes. Adding one proton makes a HUGE difference to how an atom behaves, and so deserves a new name. The neutrons hang around in the nucleus to keep the protons from kicking each other out. Exchanging electrons is important, but doesn't change the element type.

The above Landsat image from NASA shows Cape Cod, Massachusetts. This is a pile of sand and gravel out in the north Atlantic. The Cape has no large rivers, and is not especially close to any large rivers (the Connecticut and the Hudson are far out of the picture to the left). Looking along the far right-hand side of the Cape, the long white line is sand of the great outer beach (pink arrow), and sand deposits are prominent to the north and south (yellow arrows). What is going on?

The ocean is eroding the outer beach, and the yellow-arrow ends are growing more slowly, so the Cape as a whole is shrinking. You can actually see sand underwater off the yellow arrows, and that sand came from the outer beach—the Cape is losing ground. Furthermore, the Cape is losing ground much faster than nudists are losing peripherals.

Earthquakes can be caused in many different ways. The best interpretation of the planet's earthquakes is that:

The rare, deepest ones are caused by "implosion" as minerals in downgoing slabs of subduction zones suddenly switch to a denser arrangement, whereas common shallower ones are caused by elastic rebound of bent rocks when a fault breaks. "Implosion" is the currently favored idea. As subduction zones take rocks deeper where pressure is higher, the building blocks tend to reorganize to take up less space, shifting from, say, a one-on-top-of-another pattern to a fit-in-the-space-between-those-below pattern. Sometimes, this seems to be delayed and then to happen all at once (I can't move until my neighbor does...), giving an implosion. The biggest, deepest earthquakes happen where temperatures and pressures are so high that we don't think rocks can break. Humans have never made a hole anywhere nearly as deep as the deeper earthquakes. We have mostly quit testing atomic bombs. And, coffee shops just aren't buried deeply enough to account for the deepest earthquakes.

Dave Janesko is explaining the great Sevier Fault to Dr. Alley and the CAUSE class. Dave has just informed everyone that the black rocks, which formed by cooling of a very hot lava flow, are much younger than the red rocks, which formed from sediments deposited in a lake. He has examined the red rocks and found that they have not been "cooked" by heat from the black rocks, so the red and black rocks must have been placed together after the black rocks cooled. And, he has examined the contact between red and black rocks and found that it is a fault that has been scratched by the motion of the rocks along the fault. It is likely that:

The scratches are nearly vertical, because the black rocks were dropped down along a pull-apart fault to lie next to the red rock. The spreading that opened Death Valley affected a lot of the west, all the way over to Bryce Canyon in Utah. The Sevier Fault, just west of Bryce, formed as pull-apart action broke the rocks, allowing younger rocks including the black lava flow to drop down next to older rocks including the red lake sediments. The scratches are not too far from vertical, made as the rocks dropped down.

Most landslides happen when:

The unconsolidated materials on hillslopes are very wet and thus heavy and slippery, and the water doesn't have to "break" as the grains move. Dry sand can move, but even very dry times on hillsides usually don't cause landslides. But let a hurricane really saturate things, and all heck can break loose. Paving causes lots of changes, but landslides are not usually the result.

The floor of Death Valley is about two miles lower than the mountain peaks around it. How did this happen?

The valley floor has dropped by more than two miles relative to the mountains, but erosion has removed the mountain tops and the sediment produced has partially filled the valley, leaving an elevation difference of two miles. Watch a stream flowing into Death Valley (or any other valley) during a thunderstorm, and you will see that the water is full of rocks, mud, etc. The mountains are being eroded, and the loose pieces are carried down and dumped into the valley. Yet the mountain peaks are still two miles above the floor of Death Valley; the erosion and deposition are fighting against faulting that has dropped the valley by more than two miles relative to the mountains. No river carved the valley; the rivers are filling it up. And strange as it may seem, the valley is older than Congress or brewed coffee.

What is accurate about the planet's climate system?

The wind blows because heating near the equator drives convection cells in the atmosphere, and the winds appears to curve to the left or right over the surface of the planet because of friction produced by the spherical planet's rotation beneath the atmosphere. Heating near the equator causes pressure differences that drive the winds. On a rotating body, whether a flat merry-go-round or a spherical Earth, the rotation causes flows to curve. And very very very little of the wind is traceable to marmots.

Above is a "beach" at Acadia National Park. The pieces are granite.

There is no sand here, so sand must be lost to deep water fast enough in comparison to sand supply that sandy beaches have not formed. Granite does weather to make sand, so some sand must be produced, but this is not a sand deposit, so sand loss must be fast enough to prevent large accumulations. The Park Service neither mines sand from beaches, nor hides sand on beaches. And huge storms hit Florida and the Gulf Coast, but they have sandy beaches.

Based on what these pictures show, and the text accompanying them (note: erosion refers to the removal of rock material from the stones):

There may be several mechanisms of erosion, including chemical action under lichens, breaking off of chunks, and bit-by-bit removal that isn't occurring under lichens. A gravestone is "attacked" in many ways—bumped by lawnmowers, cracked as ice grows in tiny cracks on a cold night, and attacked chemically.

Hot spots are important geological features. What is accurate about hot spots?

They are rising towers of hot rock, perhaps from as far down as the core-mantle boundary, bringing heat up to feed volcanoes. Earthquakes make sound waves that go through the whole Earth, and go slower through hotter, less-dense rocks. By putting out listening devices called seismometers around the Earth, and listening to the waves from many earthquakes in many places, scientists can map the hotter regions, and find that towers of hot rock come up from way deep in the Earth in some places. But, some other hot spots don't seem to start as deep. The hot spots don't seem to move around much, but the lithospheric plates drift around over the hot spots. Hot spots come up beneath continents and oceans, and can poke through both. But no one has ever found coffee in a hot-spot plume.

If you drive for 2 hours, at 60 miles per hour, you will have traveled 120 miles. This is a very common type of calculation, involving three quantities: distance, rate and time. If you know just two of these three quantities, you can always calculate the third. Thus, if you want to know how much time it is going to take you to get somewhere, and you know that the distance is 120 miles and you will drive at a rate of 60 miles per hour, you can divide the 120 miles by the 60 miles per hour and obtain a time of 2 hours. For this exercise, you will be relating distance, rate and time. The distance we will work with is the depth of Happy Valley. (Remember that even more rock has been removed than the depth of the valley, because the site of the modern valley once was higher than the site of the modern mountain, and the site of the modern mountain has been lowered somewhat as well. And, the rocks had to be deposited, raised and bent before the erosion could occur. So, you're calculating how much time was involved in a small part of the much longer history of central Pennsylvania.) We can measure how rapidly rock is being dissolved and washed out of Happy Valley, and use some fairly simple physical ideas to turn that into the rate at which the valley floor is being lowered. That gives you a distance (the valley depth) and a rate ( the speed at which the valley floor is being lowered), allowing you to calculate the time that has been used in the lowering. To get the correct answer, you will calculate the time from which equation:

Time=Distance divided by Rate You need to calculate time, so that should be on the left. How far (distance) divided by how fast (rate) will give you time. If you remember doing this with units, time (in hours) is calculated by dividing distance (in miles) by rate (in miles per hour), because: hours=miles/(miles/hour).

Type "Alley RB" into the author space on the Web of Science. You will find lots of pages of refereed scientific literature that Dr. Alley has worked on. What was he publishing on in 1989? (Hint: the older ones are near the back, so use the "page" box near the top in the center to go there.)

Water-pressure coupling of sliding and bed deformation, and sedimentation beneath ice shelves. The Web of Science lists 4 papers that Dr. Alley helped write and that have 1989 publication dates. During earlier years, Dr. Alley had helped understand how deformation within mud under glaciers and ice sheets helped them move. Such glaciers and ice sheets also move by slipping (sliding) over the mud or rock beneath, lubricated by a thin water layer, but only if the water pressure is high enough to float the ice. In 1989, Dr. Alley helped study how sliding and bed deformation were related to water pressure. He also looked at how the moving sediment under the ice was dumped into the ocean where the ice started to float to form an ice shelf. Dr. Alley studied many other things in other years, but those were the biggies for 1989.

The picture above shows ocean in the upper right, a beach, and land in the lower left. The red dashes trace the crest of a wave. Waves move perpendicular to their crests. What principle might be illustrated by the picture?

Waves go slower in shallower water. The rotation of the Earth has only miniscule effect at scales this small. Waves do go slower in shallower water, so as one end nears the coast, that end "waits" for the other end to catch up, causing waves to be going almost straight toward the shore when they run up the beach. There certainly are non-sand-beach coasts, and Pepsi has shown no interest in buying off the professor.

Among features A, D, E, and O, which is the oldest?

feature E

*Check image Among features G, H, I, and J, which is the oldest?

feature I

Among features J, K, L, and P, which is the oldest?

feature K

Among features E, F, J, M, which is the youngest?

feature M

Among features C, D, M, O, which is the youngest?

feature O