GEOSCI 10 all questions

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.

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.

We now know a lot about the big processes that shape the Earth's geology. Which of the following is NOT correct about that knowledge?

Almost all of the motion of lithospheric plates is vertical, with almost no horizontal motion.

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.

If North America and Asia continue drifting towards each other across the Pacific at their modern rates, they must someday develop what?

An Appalachian-type or push-together obduction boundary.

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.

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 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.

Tsunamis:

Are long, low waves out in the ocean that pile up near shore because such waves, or parts of such waves, move slower in shallower water.

Weathering attacks a granite in Pennsylvania or Washington, DC, or a similarly rainy place. The quartz grains in the granite primarily: Group of answer choices

Are loosened from the rock but don't change much, staying in the soil as quartz sand.

Continents:

Are the "unsinkable" part of the solid Earth; although a little of a continent might go down, most continental material stays near the surface.

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

As the air rises up the Sierra, the air expands, making rain and snow, and cooling by 3 degrees F per thousand feet upward.

What geological processes have caused the Grand Canyon to be wider at the top than at the bottom?

As the river cuts down, the steep walls of the canyon experience mass movement (rocks fall, slump, creep or otherwise move off the walls and down to the river), so the top of the canyon is widening as the river deepens the bottom.

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 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 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.

Which formula most closely describes the process by which plants make more of themselves:

CO2 + H2O + energy → CH2O + O2 CaCO3 is shell or cave-rock; the equation with CaCO3 on the left is dissolution of rock to make caves, and 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.

During the most recent ice age:

Central Pennsylvania was just beyond the edge of the Canadian ice.

If you went swimming in the single channel of this river, and grabbed a sample of the river bank, what would you likely come up with? Group of answer choices

Clay, that sticks together and can hold up steep slopes.

The United Nations, under the auspices of the Intergovernmental Panel on Climate Change, has attempted to assess the scientific understanding of how greenhouse-gas emissions will affect the climate, and thus people. The UN reports show that if we continue on our present path, burning fossil fuels at a faster and faster rate:

Climate will change, primarily getting warmer, and those 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), 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.

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.

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).

What probably happened to create the two rocks with the orange surfaces, seen in the center of the above picture from Greenland?

Expansion from water freezing in the crack wedged the rock apart

When humans build or raise levees along big rivers such as the lower part of the Mississippi, we are likely to cause:

Fields and roads on the flood plain to drop below the surface of the river, because compaction of flood-plain mud will no longer be balanced by sediment accumulation during floods. "Long, long, time ago, I can still remember how the river used to mend with mud..." The continuing compaction of the sediment along the lower Mississippi should be balanced by new deposits on top; stopping the new deposits does not stop the compaction, so the surface of the flood plain sinks. Even racing around curves, rivers don't tilt much, and mud compaction doesn't do much to meandering. "With a pink carnation and a pickup truck..."

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.

As rain falls through air, the water typically:

Gains carbon dioxide (CO2) from the air, becoming a weak acid

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.

The consensus of the world's climate scientists, as generated by the UN-sponsored Intergovernmental Panel on Climate Change (IPCC), is that:

Human activities have raised CO2 levels in the atmosphere, warming the planet, and the changes so far have been small compared to the changes that are likely over the next centuries unless we humans alter our behavior. Human activities have raised CO2 in the atmosphere, but if we continue with business as usual, we haven't seen anything yet—we haven't even doubled CO2, but a quadrupling or even octupling seems possible. Chlorofluorocarbons used as refrigerants are responsible for the ozone hole, and cow flatulence is not greatly affected by external methane levels, which are rising in any case. Besides, bovine belching is a larger methane source than is outlet through the other orifice.

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

Icebergs/continents are less-dense than the stuff they float in.

Given the materials presented in this class about the formation of caves, it is likely that most large caves are formed:

In limestone in moist climates.

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.

One way to treat a dying beach is to dig up sand somewhere and dump it on the beach. What is this likely to accomplish?

It causes the beach to lose the new sand over the next year or years, as the extra sand is washed back to deep water by waves and currents. 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.

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."

In the picture above, the dark stripes on the surface of the glacier are:

Medial moraines, rocks picked up from points where tributary glaciers flow together.

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.

A larger national park and a smaller national park, otherwise identical, are completely surrounded by cornfields and Walmart parking lots, and have been surrounded for a century. You count the number of species of trees in each park. You probably will find:

More species in the larger park, because it can hold more individuals thus reducing the risk of extinction. Diet Pepsi distributors are too smart to go around pouring drinks on beetles and bison; the bison might butt back! For evolution to make new species usually will take thousands of generations or longer, so a century is not long enough for new types to have appeared. The larger populations, which help prevent extinction, that are possible in the larger park will cause it to have more species.

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.

In the photograph above, a portion of cliff about 30 feet high is shown. From what location in the Grand Canyon did Dr. Alley take this image?

Near the bottom, where the river has cut through rocks that were cooked, squeezed, and partially melted deep in an old 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.

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.

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 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.

What tectonic setting is primarily responsible for producing Crater Lake?

Push-together subduction.

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.

Lithospheric plates can interact in many ways at the long boundaries where they meet. Which of the following options includes the main patterns of interaction that are observed along these boundaries:

Push-together, pull-apart and slide-past.

In a humid-temperate climate such as that of Pennsylvania or Washington, DC, weathering breaks down granite to produce:

Quartz sand, clay, and rust, that stay to help make soil, while some ions dissolve and wash away.

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.

Geologically speaking, the water table:

Rises during or soon after rainstorms as spaces fill up, and sinks during droughts as water drains away.

What happened in the picture above?

Rivers have delivered sediment to the sea, forming deltas that built up as they built out so that they still slope slightly downhill toward the sea.

What happened in the picture above?

Rivers have delivered sediment to the sea, forming deltas that built up as they built out so that they still slope slightly downhill toward the sea. Two deltas have formed where streams carry sediment from the hillside into the fjord in South Greenland. The main source of sediment is the streams from the land, not suspended sediment already in the sea water. And the deposits cannot be purely flat-topped, or the rivers would not flow across to get to the sea water in the fjord. Mollusks do live along the coast but are not being protected by intrusive changes to the coastline, nor do enough people visit here to be worth advertising Delta Airlines.

Acadia is beautiful even in the rain and fog, but the park still doesn't have many sandy beaches, and this is surely not a sandy beach, the rocks are granite, broken off the granite bedrock. Why aren't there sandy beaches?

Sand is produced or supplied slowly enough, and sand loss to deep water is fast enough, that sandy beaches do not form. 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 would not allow sand mining, and New Jersey would just go offshore to deeper water to dig up sand. And huge storms hit Florida and the Gulf Coast, but they have sandy beaches.

If you went swimming in one of the channels of the river pictured above, and grabbed a sample of the river bank, what would you likely come up with?

Sand or gravel, that collapses to plug channels. This is a braided channel, and these normally are fairly broad and shallow, forming where the banks are sand and gravel and don't hold up steep slopes. Sand castles can be steep, but if they get too wet or too dry, they fall down to gradual slopes, and there almost always is wetting or drying sometime during a year.

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.

In the picture above, the yellow arrow points at a jetty, a sort of sea wall or groin or dam, that was constructed along the coast of Washington. A likely interpretation of what you see here is:

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.

Geologically speaking, the water table:

Separates the water-filled region below the Earth's surface from the region closer to the surface in which some air exists in the spaces. The water table is the surface below which all the spaces are full of water, but above which there is generally some air in the spaces. During droughts, water drains away from the ground to the creeks, so air enters spaces previously occupied by water, and the water table drops in elevation. Creeks do change in elevation between rain and drought (floods happen...). And while there might be bottled water in the Capitol, geologically speaking, that is not the right answer.

Sandy beaches:

Shrink if the sand supply from rivers or coastal erosion is smaller than the sand loss to deep water, and grow if sand supply exceeds the sand loss, remaining in balance if sand supply equals sand loss.

Mass wasting delivers sediment to streams. We believe that in regions such as Pennsylvania or the hills around Washington, DC, most of the mass that is delivered to streams arrives by:

Soil creep, slow motion of pieces from freeze-thaw action, throw by falling roots, downhill motion of rocks during digging of gopher holes, etc.

In the Great Smokies:

Some older rocks were shoved on top of younger ones by push-together thrust faulting.

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.

We humans are changing the composition of the atmosphere in many ways. Those changes will directly affect the planet's temperature, but the resulting change in temperature will affect other things on the planet that also affect the planet's temperature. Suppose that we could magically change the composition of the atmosphere enough to raise the temperature one degree if all other parts of the Earth system were held fixed, and after the warming, we allowed the other parts of the Earth system to react for a few years or decades. At the end of that time, what would be the total change in the Earth's temperature?

The Earth would end up a few degrees warmer than before the human influence, because positive feedbacks would amplify the original change. 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.

The top picture from the coast of Greenland, and the bottom picture from Bear Meadows Natural Area in central Pennsylvania, are geologically related. How?

The Greenland picture shows rocks that have been creeping downhill on permafrost, and Bear Meadows probably was formed when such a creeping mass dammed a stream during the ice age.

In the picture above, when Dr. Alley slices his finger through the sand, he is recreating on a smaller scale what type of geologic process?

The action of mass wasting, as soil and rock collapses off of newly steep canyon walls initially carved out by water.

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? (North Pole and Equator)

The equator is hotter than the pole because the sun hits the equator directly but the sun hits the pole a glancing blow

Large rivers have many interesting features, including:

The flood plain, the nearly flat region farther from the river than the natural levees and composed of mud deposited by the river's floods. 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.

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.

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

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.

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.

The above Landsat image from NASA shows Cape Cod, Massachusetts. The short yellow arrow indicates new sand deposits, which have formed over the last decades. The long pink arrow indicates underwater sand deposits. The dotted blue arrow points to the great Outer Beach of the Cape. Based on material presented in this class, what is going on?

The ocean is eroding the blue-arrowed outer beach, and the yellow-arrowed end is growing more slowly, with some sand falling off to the pink-arrowed deposits and then off into deeper water, so the Cape as a whole is shrinking. The blue-arrowed Outer Beach is eroding, losing some sand to the yellow-arrowed Monomoy Island—a remarkable birding spot—and some sand to the pink-arrowed underwater bars, which lose sand to deeper water—the Cape is losing ground. Furthermore, the Cape is losing ground much faster than nudists are losing peripherals.

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.

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.

Sea level can change locally for many reasons, but averaged over all of the oceans of the world:

The seas are rising, because warming is causing the ocean water to expand and mountain glaciers to 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.

Soil is produced by weathering of rocks. In the natural state of affairs, on a hillside covered by soil:

The soil thickness tends to a nonchanging value as production is balanced by removal, but you may have to watch for a while, as sometimes production may go faster and sometimes removal may go faster.

What happens to most living things, after they die?

They are recycled, usually by being "burned" with oxygen to provide energy for other living things, or to provide energy to fires. Nature is a very efficient recycler, so almost everything that lives is recycled. The recycling is usually achieved through slow "fires" in other living things (including you!), using oxygen. However, sometimes a "real" fire such as a forest fire will do the job.

The things that glaciers deposit include:

Till (which is unsorted) and outwash (which is sorted).

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.

The picture above shows a region of hard rock about six inchesacross from the Grand Canyon. The shape and polish of the rock areinteresting. It is likely that the rock:

Was scratched and polished by silt-laden river water, during carving of the Canyon by the Colorado River. The Canyon was carved by the Colorado River. Glaciers have not been there, and while wind, faults and mule hooves all can change the appearance of rocks, none makes something like this river-polished rock, as you saw in the class materials including in one of the Grand Canyon slide shows.

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.

In the photo above, the jetty (which is a big wall, and could also be called a groin) was constructed out from the coast in the state of Washington. The water is shallow very close to the jetty, and deeper as you move away to left, right, or off the end of the jetty at the lower right. Look at the pattern of waves, which tells you that:

Waves go slower in shallower water. Waves do go slower in shallower water. Waves coming in from the sea are held up along the jetty, so the crests become more and more curved with the ends nearest the jetty falling behind as the waves move inland.

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

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

At the beach, you can build really good sand castles:

When the sand is damp, because water is attracted to sand grains and to other water; thus, pulling sand grains apart when damp requires "breaking" the water, which is not easy.

A dam is built on a river that has a river bed that is primarily sand. You have a house just downstream of the dam, and you like to go trout fishing in the river in front of your house. A few years after the dam is built, it is likely that:

You will have built a ladder or steep path to get down to the river, because the clean water released by the dam will have washed a lot of the sand away and lowered the elevation of the river in front of your house. The stream will slow where it enters the new lake, and so will deposit sediment to form a delta rather than cutting downward or having no change. As the delta builds out into the lake, the upstream end of the delta must build up so that the stream still slopes downward, and this will tend to bury fields upstream. Meanwhile, 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, while erosion occurs downstream.

Suppose that all the rainfall that fell during an average year on a typical surface in central Pennsylvania just stayed there as a layer of water (and all the snow melted, and the melt just stayed there). If at the end of the year you were standing on your head on that surface (assuming you are a typical-sized human being), what would be true? (In an average year, Pennsylvania gets about the same amount of precipitation as the average for the world.)

You would be breathing by SCUBA or snorkel, because the water would be up between your belly button and your knees somewhere. 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, which would be up to your knees or so if you were standing on your head, so you'd need the SCUBA gear.

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

the blue/orange one

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.)

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. Never, because all sinkholes drain to Michigan. 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.)

When we speak of the Mississippi Delta, most people mean some interesting region in Louisiana with good music and seafood. Geologically, however, the Mississippi Delta is:

A river-built deposit that is several miles thick at its thickest point, and extends from near St. Louis, Missouri to the Gulf of Mexico. 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!