S370 Final Exam

How does a rotational slide differ from a translational slide?

A rotational slide takes place along a curved surface, while a translational slide takes place along a straight surface.

Explain why prehistoric cave dwellers never saw a dinosaur.

According to table 1.2, page 22, dinosaurs became extinct 70 million years ago, and hominids didn't appear until 5 million years ago.

According to plate tectonic theory, where are crustal rocks created? Why doesn't Earth keep getting larger if rock is continually created?

Crustal rocks are created at the spreading centers (divergent plate boundaries) but they melt back into the mantle ant convergent plate boundaries.

How do batholiths form?

In the section "Intrusive Bodies", subsection "Intrusives that Crystallize at Depth", paragraph 2, it is explained that according to current theories, batholiths are formed by the coalescence of smaller plutons. Blobs of magma work their way upward and collect 5 to 30 kilometers below the surface.

The mineral fluorite (CaF 2 ) is composed of calcium (Ca 2 1 ) and fluorine (F 2 ). What kind of bonding holds them together? Explain how you know this.

It's an ionic bond because calcium has only two electrons in its outermost shell and fluorine has seven. So when calcium and fluorine bond together the outermost calcium electrons spend most of their time going around the fluorine atoms, creating a positive ion and a negative ion.

Why isn't the land surface of Earth flat after millions of years of erosion by mass wasting as well as by other erosional agents?

It's true that erosional forces gradually flatten the land, but as we will see in chapter 20, tectonic forces are constantly creating new mountain ranges, such as the Himalayas, which are becoming taller even now.

Describe the appearance and origin of seamounts and guyots

Seamounts originate near spreading centers. If they begin as islands and then sink below the surface they acquire flat tops because of wave erosion. In this case they're called "guyots".

In a sketch, show how and why sand moves along a beach face when waves approach a beach at an angle.

See the Chapter 14 Study Questions

Draw diagrams illustrating the three types of unconformity. How can you determine that: a. An unconformity you are examining is a nonconformity and not an angular unconformity?

See the Chapter 8 Study Questions

Describe Earth's magnetic field. Where is it generated?

The Earth's magnetic field behaves as if it were generated by a giant bar magnet inside the Earth, with the north magnetic pole at the south end and the south magnetic pole at the north end. It is actually generated by currents within the Earth's metallic outer core.

An aquifer is a. a body of saturated rock or sediment through which water can move easily. b. a body of rock that retards the flow of groundwater. c. a body of rock that is impermeable.

a. a body of saturated rock or sediment through which water can move easily.

The last episode of extensive glaciation in North America was at its peak about _____ years ago. a. 2,000 b. 5,000 c. 10,000 d. 18,000

d. 18,000

Continental glaciation a. is found in mountainous regions. b. only occurred during the last ice age. c. is a glacier found in the subtropics of continents. d. exists where a large part of a continent is covered by glacial ice.

d. exists where a large part of a continent is covered by glacial ice.

What process causes the asthenosphere to melt, generating magma at (a) a convergent boundary; (b) a divergent boundary?

(a) According to figure 3.28, the wet mantle material partially melts because it is lighter than the surrounding material, and therefore rises. As it rises the pressure decreases, and this causes partial melting. (b) According to figure 3.26, the mantle material rises to fill the void left by the diverging tectonic plates, and the decrease in pressure causes "decompression melting".

How does a graded bed form?

A graded bed is illustrated in figure 6.29 on page 147. It forms when heavier particles are deposited first, then progressively lighter ones. The formation of bedding by turbidity currents is described in the paragraph opposite the diagram.

What is the difference between a joint and a fault?

A joint is just a fracture or crack in a rock. If the rock moves in different directions on different sides of the rock then it's a "fault".

How do kettles, eskers, and drumlins form?

A kettle forms when a piece of a glacier breaks off and forms a depression in the ground. An esker is a long hill that is formed from sediment that is deposited by a stream that flows under a glacier. A drumlin is apparently formed when a glacier moves over material that was deposited during a previous period of expansion. We don't know for sure.

What is a mantle plume? What is the geologic significance of mantle plumes?

A mantle plume is a narrow column of hot mantle material the rises through the mantle until it reaches the surface and forms a "hot spot". The significance of these mantle plumes is that they often form volcanoes on the surface and the apparent motion of these volcanoes can be used to determine the actual motion of the tectonic plate. The mantle plume itself is stationary.

How would you expect the appearance of a rock high in iron and magnesium to differ from a rock with very little iron and magnesium?

A rock high in iron and magnesium will be darker in color. In class I showed you a sample of biotite, which is a type of mica that is high in iron and magnesium, and a sample of muscovite, which is not high in iron and magnesium. These are both varieties of mica, but the biotite is darker in color.

How does a structural dome differ from a plunging anticline?

A structural dome curves in three dimensions: If you tried to make a figure like this out of paper you would crinkle the paper. On the other hand a model of an anticline can be made just by taking a flat sheet of paper and bending it. See the illustration in question 4. Making it "plunge" just requires tilting it lengthwise. In geometry we would say that a dome is "intrinsically curved" while a fold is "intrinsically flat".

A subduction zone can be regarded as a very large example of what type of fault?

A subduction zone can be regarded as a very large example of a thrust fault. See figure 1.12 B in chapter 1.

What is a transform fault? What type of transform fault is the San Andreas fault?

A transform fault is a strike-slip fault, as described in chapter 15. The two sides of the fault move horizontally past each other. The San Andreas fault is a right transform fault. If you stand on the west side of the fault and look east, the east side of the fault seems to be moving southward. If you stand on on the east side of the fault and look west, the west side of the fault seems to be moving northward. So in each case the other side of the fault seems to be moving right relative to your side. See box 19.1, figure 2.

How do earthquakes cause tsunami?

A tsunami is a very long-wavelength wave where the elliptical motion illustrated in figure 14.3 reaches all the way to the bottom of the ocean. It can be caused by earthquakes when they occur on the ocean floor.

Describe how a caldera forms.

According to "Types of Volcanoes", subsection "Calderas", paragraph 1, "a caldera can be created when a volcano's summit is blown off by exploding gases or when a volcano (or several volcanoes) collapses into a partially emptied magma chamber".

What factors control whether a rock behaves as a brittle material or a ductile material?

According to figure 15.4, all rocks behave elastically when the stress is relatively low. But when the stress exceeds a certain level, some rocks exhibit brittle behavior, which means they break, and others exhibit ductile behavior, which means they bend. The difference between the two depends on the type of rock and also on the temperature and pressure, as explained in chapter 7, section "Metamorphism", paragraph 8.

What rock would probably form if magma that was feeding volcanoes above subduction zones solidified at considerable depth?

According to figure 3.28 the magma is more mafic at greater depth, so a rock that formed there would have lower silica content.

What are the effects on metamorphic minerals and textures of temperature, confining pressure, and differential stress?

According to section "Factors Controlling the Characteristics of Metamorphic Rocks", subsection "Temperature", minerals that are stable at high temperatures tend to be less dense than minerals that are stable at low temperatures. This is because high temperatures cause the atoms to vibrate more, and a more open crystal structure allows greater vibration. Increasing pressure has the opposite effect of increasing temperature. It tends to create minerals that are more compact, and therefore more dense. Differential stress causes rocks to be more compact in one direction than in the other direction. This can produce "foliation", which means that the crystals tend to be oriented in one direction. Slate, phyllite, schist and gneiss are examples of foliated rocks.

What is the difference between feldspar found in gabbro and feldspar found in granite?

According to table 3.1, feldspars found in granite are white, light gray or pink, whereas feldspars found in gabbro are medium to dark gray. This is because gabbro has a higher concentration of iron and magnesium, whereas granite has more aluminum and sodium.

Why is a higher temperature required to form magma at the oceanic ridges than in the continental crust?

According to the section "Explaining Igneous Activity by Plate Tectonics", subsection "Igneous Processes at Convergent Boundaries", paragraph titled "The Origin of Granite", the melting point of silicic rocks is lower than that of mafic rock, especially if water is present. (If water is present it's called "flux melting".)

Name and describe the three main ways in which a stream transports sediment.

According to the section "Stream Transportation of Sediment", the three main ways that a stream can transport sediment are bed load, suspended load and dissolved load. These are illustrated in figure 10.13. The bed load is rolling or bouncing along the bottom, the suspended load is floating along in the stream, and the dissolved load consists of ions mixed in with the water molecules.

Describe three ways in which a river erodes its channel.

According to the section marked "Stream Erosion", streams erode rock and sediment in three ways: hydraulic action, solution and abrasion. Hydraulic action is simply the ability of the water itself to pick up particles of sediment. The faster the water flows, the more sediment it can pick up, as shown by the graph in figure 10.7. Solution means dissolving minerals in the streambed and carrying them as ions. Abrasion means that particles that have already been picked up by hydraulic action can scrape the bottom of the stream and cause more material to be eroded.

What is albedo? Give an example of an object with (a) high albedo and (b) low albedo.

Albedo is the percentage of radiation reflected from a surface. Snow has a high albedo; soot has a low albedo.

Examine the photo of the Canadian Rockies on the first page of this chapter. Which of the four Earth systems can you see? How are they interacting with each other?

All four Earth systems are visible in this photograph. The clouds are part of the atmosphere; the glacier and lake are part of the hydrosphere; the grass and trees are part of the biosphere; and the rocks are part of the geosphere.

Describe how arêtes, cirques, and horns form.

An arête is a ridge between two valleys carved out by alpine glaciers. A cirque is illustrated in figure 12.18. It is a circular depression formed at the top of a mountain by accumulating snow. When the snow and glacial ice reach the top of the cirque it spills over and forms a valley glacier. A horn is formed when cirques and valley glaciers have eroded a mountain on three or more sides.

Write out the definitions for the terms element, mineral , and rock; then for each of the following substances, determine whether it is an element, a mineral, or a rock. a. Iron b. Quartz c. Granite d. Limestone e. Calcium f. Calcite g. Obsidian h. Diamond i. Carbon

An element is a substance with a given number of protons in each nucleus. A mineral is a naturally occurring, inorganic, crystalline solid that has a specific chemical composition. Rocks are naturally formed aggregates of minerals or mineral-like substances. The elements in the list are a, e, i; the minerals are b, f, h; the rocks are c, d, g.

How could fossils in a terrane's rocks be used to indicate that it is an exotic terrane?

An exotic terrane is a piece of a mountain belt that originated a long distance away. (See figure 20.22.) So if the fossils don't seem indigenous to the region, the terrain may be exotic.

Why is it desirable to find an index fossil in a rock layer? In the absence of index fossils, why is it desirable to find several fossils in a rock unit to determine relative age?

An index fossil is a fossil of an ancient species that only existed for a short time. If you find this fossil it narrows doen the age of the rock to within a small range. If you can't find an index fossil, the next best thing is a set of fossils whose ranges overlap. For example, if one species existed from 240 million to 180 million years ago and another species existed from 190 million to 150 million years ago, and you find fossils of both of them in the same rock, then you know that the rock must be between 180 and 190 million years old.

How does a confined aquifer differ from an unconfined aquifer?

An unconfined aquifer is only partially filled with water. The surface between the saturated layer of the aquifer and the empty layer above it is called the "water table". A confined aquifer is completely saturated with water. There is usually a layer of relatively impermeable rock separating it from the next layer above it. In southeastern Wisconsin the Cambrian-Ordovician sandstone and dolomite aquifer is covered with a layer of shale, separating it from the Silurian dolomite aquifer.

Which mineral weathers faster—hornblende or quartz? Why?

As explained in table 2.1, hornblende is the most common mineral in the amphibole group. If you look at figure 2.12 you see that amphibole consists of double chains in which each silica tetrahedron is bonded to two or three other tetrahedra. In quartz, on the other hand, each silica tetrahedron is bonded to four other tetrahedra. So quartz has stronger bonding than hornblende and is therefore more resistant to weathering.

Describe two different origins for the continental rise.

As explained in the textbook, some continental rises consist of sediment that was deposited by turbidity currents while others are formed by ocean currents that flow along the sea bottom. The two types can be distinguished by the type of bedding: graded bedding of coarse layers probably means the sediment was transported by turbidity currents.

Why is the Earth much less cratered than the Moon?

As explained on page 574, most of the craters on Earth have been obliterated by weathering, erosion, volcanism and plate tectonics. There are a few places where we may be able to see the remains of ancient craters. For example, the southeast part of Hudson Bay forms a round structure that was once believed to have been formed by a meteor impact: Nastapoka arc (from Wikipedia) Detailed studies have shown no evidence of shatter cones, radial fractures or shock metamorphism, so most geologists now believe that this circular arc was formed by tectonic activity. However, some believe that this tectonic activity conformed to an earlier crater that dates back to the Archean eon. Likewise the Silurian dolomite basin, a round structure that underlies lower Michigan and parts of surrounding states, including southeastern Wisconsin, was once believed by some to be the result of an ancient asteroid impact, but no evidence has been found to support this. Craters that have been positively identified on Earth include Meteor Crater in Arizona, which was formed about 50,000 years ago, the Sudbury astrobleme, which goes back 1.8 billion years, the Vredefort crater in South Africa, which is 2 billion years old, and the 2.4 billion year old Suavjärvi crater in Russia. The craters of the Moon that we can see through a telescope were formed over four billion years ago, when bombardment by large meteors was much more frequent. The "maria" or "seas" are basaltic plains that were formed after the main bombardment ended. That's why there are relatively few craters within the maria. The planet Mars has a relatively large number of craters, which indicates that geologic activity on Mars ceased billions of years ago.

Name four types of sand dunes and describe the conditions under which each forms.

Barchan dunes develop where the sand supply is limited. Transverse dunes require a greater sand supply. Parabolic dunes also require large amounts of sand, and generally develop around "blowouts", depressions caused bywind erosion. Longitudinal dunes apparently require crosswinds. The reasons for their regular spacing are not completely understood.

Why is the rock of the deep-sea floor (60% of Earth's surface) basalt? Where did the basalt come from?

Basalt is a type of mafic rock that comes from the Earth's mantle. It erupts at mid-oceanic ridges and becomes new seafloor.

Why are some parts of the lower mantle hotter than other parts?

Because there are regions that have a greater concentration of radioactive materials, and these generate a greater amount of heat.

How does a sedimentary breccia differ in appearance and origin from a conglomerate?

Breccia consists of particles with jagged edges, whereas conglomerate has particles with rounded edges. Rounding takes place when the particles are transported by water.

A dike cuts through a granite stock, which contains inclusions of the surrounding sandstone layer. In what order did these three units form?

By the principle of cross-cutting relationships, the dike is younger than the granite stock. By the principle of inclusions, the granite stock is younger than the surrounding sandstone layer. Therefore the three units formed in the order: sandstone layer, granite stock, dike.

This is explained in the section "Intrusive Bodies", subsection "Intrusives that Crystallize at Depth", paragraph 4. Felsic magma (which is higher in silica content) is more viscous than mafic magma.

Check out figure 3.5. Granite has a wide range of compositions, but it usually contains quartz or potassium feldspar, in addition to other minerals. Diorite and gabbro both contain ferromagnesians and plagioclase feldspar, but diorite has more amphibole and gabbro has more pyroxene.

What is the origin of coal?

Coal is discussed in the section "Organic Sedimentary Rocks". It originates from plant material that has not completely decayed.

Why are volcanic eruptions at convergent plate boundaries typically more explosive than those at divergent plate boundaries?

Convergent plate boundaries give rise to felsic volcanoes, which have viscous lava, while divergent boundaries produce mafic lava

How has deep-sea drilling tested the concept of plate motion?

Deepsea drilling has enabled us to examine cores that are taken from the ocean floor and to determine their ages directly. These ages are usually determined by examining fossils rather than by radiometric dating of igneous rocks. We find that the actual age of the seafloor correlates closely with the age predicted from magnetic anomalies.

Describe the various types of plate boundaries and the geologic features associated with them.

Divergent plate boundaries: These ususlly form mid-oceanic ridges, although they occasionally occur on land, as in Iceland. Convergent plate boundaries: If they occur between two continents they can form tall mountain ranges, such as the Himalayas. If they occur between an ocean and a continent, then the oceanic plate is subducted under the continental plate and an oceanic trench is formed on one side, while a mountain range such as the Andes is formed on the other side. If both plates are oceanic plates then one is subducted under the other and they form an island arc.

Describe the difference between effusive and explosive eruptions in terms of their eruptive products and the hazards they pose to society.

Effusive eruptions produce continuous lava flows. They are described in the section "The Eruptive Products of Volcanoes", subsection "Effusive Eruptions". The lava is usually basaltic since basalt is mafic and therefore less viscous. In Hawaii the Pu'u O'o vent erupted in this way between 1983 and 2018. The main hazard is that the lava may bury roads or buildings. Explosive eruptions are much more dangerous. They emit various pyroclastic materials. These are summarized in the subsection "Explosive Eruptions", paragraph "Pyroclastic Materials". Note the difference in size between dust, ash, cinders, lapilli, blocks and bombs. There's a picture of a pyroclastic flow in figure 4.14.

What does the presence of an estuary imply about the recent geologic history of a region?

Estuaries are drowned river mouths. They form because sea level has risen in the recent past. A "fiord" is similar to an estuary but it consists of a drowned glacial valley. Fiords are found along coastlines in previously glaciated areas, including Scotland, where they are called "firths".

How do evaporites form? Name two evaporites.

Evaporites form when a body of water evaporates, causing dissolved minerals to precipitate. Two examples of evaporites are gypsum and halite (salt). In fact, the salt that is used on icy streets in Milwaukee comes from a salt deposit under the dolomite basin near Green Bay. It formed when an inland sea evaporated hundreds of millions of years ago.

What is the temperature distribution with depth into Earth?

Figure 17.23 shows how temperature increases with depth. The width of the red bar indicates the uncertainty in the data. The temperature of the center of the Earth is between 6000 and 7500 degrees C

What conditions are necessary for an artesian well?

For an artesian well to operate, there must be a confined aquifer that slopes downward from a higher elevation to a lower elevation. The water in the lower part of the aquifer is under pressure, and if a well is drilled the water will gush upward without having to be pumped.

How could fracture zones have formed?

Fracture zones form as a result of the seafloor being unable to spread uniformly, due to the curvature of the Earth.

Describe at least three processes that mechanically weather rock.

Frost wedging: water seeps into cracks in the rock, then freezes. Since water expands when it freezes, this tends to break the rock apart. Pressure release: as explained in question 1, some minerals are less stable at low2 pressures than at high presures, so when erosion brings them to the surface, they tend to disintegrate. Extreme changes in temperature: When a rock repeatedly expands and contracts, it tends to break the rock apart. This is the same process that causes light bulbs to burn out: the filament repeatedly expands and contracts as it goes from room temperature to 2000°C and back.

what way do greenhouse gases warm the planet?

Greenhouse gases are transparent to sunlight but they absorb longer-wavelength radiation coming from the ground. So the heat is trapped in the Earth's atmosphere.

Why are most of North America's hot springs and geysers in the western states and provinces?

Hot springs and geysers require a body of magma, which is usually associated volcanism and tectonic activity, to heat the water. These conditions occur in the western United States.

How do scientists use ice cores to determine past temperatures?

If the ice has a higher concentration of the isotope 18O it was formed in a cooler climate; if it has a lower concentration of 18O it was formed in a warmer climate. This is similar to the use of foramimifera fossils that was described in chapter 2, box 2.1. We can also measure the concentration of greenhouse gases trapped in air bubbles in the ice.

Why do some rocks fold while others are faulted?

If the rock is ductile it folds; if it's brittle it faults. Rocks become ductile when the temperature and pressure are high enough.

What geologic processes might cause the forces that can hold a region out of isostatic equilibrium?

If there are forces other than gravitational forces and buoyant forces, then Archimedes' principle may not apply. Tectonic forces such as one plate pushing on another can hold a region out of equilibrium.

What are the three major types of rocks?

Igneous, sedimentary and metamorphic.

Describe the evidence that South America and Africa were once joined.

In addition to the similarity in coastlines, there is also fossil evidence that South America and Africa were once joined: as illustrated in figure 19.3 of your textbook, the fossils of Cynognathus occur on both sides of the Atlantic, although Cynognathus was a land creature; and the fossils of Mesosaurus occur on both sides although Mesosaurus was a freshwater swimming reptile that could not have crossed the ocean. There is also geological evidence: similar rock formations are found on both sides of the Atlantic, as shown in figure 19.11. The picture also shows evidence of ancient glaciation that started in Africa and moved into South America.

How might a warming trend cause increased glaciation?

In box 12.2, under "Galloping Glacier", it is explained that if water builds up under a glacier it can cause the glacier to expand more rapidly. This can be triggered by an increase in temperature.

If subducting plates can penetrate the 670-kilometer mantle boundary and sink all the way to the base of the mantle, why are there no earthquakes deeper than 670 kilometers?

In order for an earthquake to occur there must be a buildup of tension between two plates. Below 670 kilometers the rock is so fluid that it slides without sticking and there are no earthquakes.

Explain what happens chemically when calcite dissolves. Show the reaction in a chemical equation.

In table 5.1 the book lists two reactions: CaCO3 + CO2 + H2O ⇄ Ca++ + 2HCO3- , CaCO3 + H+ + HCO3- ⇄ Ca++ + 2HCO3- The second reaction makes use of a hydrogen ion that is produced by the dissociation of a carbonic acid molecule, as described by equation A in table 5.1.

Describe the different methods used to study the sea floor.

In the lecture I described echo sounding. If lower frequencies are used the sound waves can penetrate the seafloor, with some energy bouncing back at each layer of rock. As long as there is a difference in wave speed between one layer and the next some fraction of the wave energy will be reflected. There are also direct methods of studying the seafloor. The Challenger expedition retrieved samples by lowering a dredge the the seafloor and scooping up material. More modern methods include "corers", which are weighted pipes, and seafloor drilling. Submersibles have been used to explore the seafloor visually. An early type of submersible was called a "bathyscaphe". It was designed like a blimp, but instead of being filled with helium it was filled with gasoline, which is lighter than water. Jacques Piccard explored the Challenger depth in a bathyscaphe in 1960. Nowadays submersibles resemble small submarines. ALVIN, pictured in figure 18.2, is an example. A remotely operated submersible is pictured in figure 18.3.

What are the three components of volcanic hazard mitigation? Provide examples of each.

In the same subsection cited in the previous answer, it is stated that the three main components of volcanic hazard mitigation are: hazard mapping, monitoring, and alerts. In the answer to question 9 we gave examples of monitoring. Hazard mapping involves the study of deposits from past eruptions. Alerts include those that were given to the public prior to the Mount St. Helens eruption, and alerts given to airlines during the eruptions in Iceland.

You are a volcanologist working on a volcano that has been active in the past but is currently quiet. What methods would you use to monitor this volcano, and what would those methods tell you about processes beneath the surface?

In the section "Living With Volcanoes", subsection "Monitoring Volcanoes", various methods of monitoring volcanoes are described. Most volcanoes show signs of unrest weeks or even months before erupting. Seismographs monitor seismic activity as the lava flows toward the surface. Volcanologists also use instruments to measure ground height; sometimes the ground rises as magma flows underneath it. Temperature increases can also indicate the presence of magma, as well as changes in the amount of gas emitted by the volcano.

Where were the metals before they were concentrated in hydrothermal vein ore deposits?

In the section "Types of Metamorphism", subsection "Hydrothermal Metamorphism", it is explained that metasomatism occurs when ions are transferred from the cooling magma to the ore deposits.

Using the Appalachian Mountains as an example, describe the Wilson Cycle.

It is believed that when the Appalachians were formed there was a subduction zone where two tectonic plates were coming together. Eventually the continents merged and became a single continent. But then it began to split along a rift which eventually became the Atlantic Ocean. This process will presumably repeat itself in the future.

What does a trellis drainage pattern tell about the rocks underneath it?

It tells us that the underlying rocks are in the form of synclines and anticlnes, as described in chapter 15, rather than domes and basins (also described in chapter 15). The synclines and anticlines cause rocks to erode along parallel lines, producing parallel valleys with straight hills between them.

What is karst topography? How does it form?

Karst topography occurs where there is an underlying layer of limestone (CaCO3) or other carbonate rock. When this is dissolved by groundwater, it forms caverns, which can collapse to form sinkholes. There is a picture of karst topography an figure 11.22.

Compare lava flows, pyroclastic flows, and lahars as volcanic hazards.

Lava flws are relatively harmless as long as they are slow enough so people can get out of the way. Pyroclastic flows are very dangerous. Hot pyroclastic surges were responsible for most of the deaths when Vesuvius erupted in 79 AD. Lahars are volcanic mudflows. 23,000 people were killed when a lahar buried the town of Armero, Colombia in 1985.

Why is burial usually necessary to turn sediment into sedimentary rock?

Lithification usually requires compaction and cementation. For compaction you need a lot of pressure, so the sediment usually has to be buried.

What is a magnetic reversal? What is the evidence for magnetic reversals?

Magnetic reversals happen every few hundred thousand years. The magnetic field changes direction from south to north or from north to south. This is recorded in igneous rocks. The magnetite crystals within the rocks will have their magnetic fields oriented in the direction of the Earth's magnetic field at the time when the rocks cooled below their Curie point.

How does material deposited by glaciers differ from material deposited by streams? What is the name of a rock formed from this material?

Material deposited by glaciers is unrounded and unsorted. A rock that is deposited by a glacier is called an "erratic". The parking lot at the Greenbush Kettle is bordered with glacial erratics that were found in the kettle. They were transported from northern Wisconsin and upper Michigan by the glacier

How can mechanical weathering speed up chemical weathering

Mechanical weathering increases the amount of surface area that is exposed to the environment. This is illustrated in figure 5.10: In this example the surface area goes from 6 square meters to 12 square meters, while the volume remains constant at on cubic meter.

Why are most beds of sedimentary rock formed horizontally?

Most beds of sedimentary rock are formed horizontally because the sediment from which the rock is formed is deposited in horizontal layers, often in bodies of water.

Discuss the distribution of earthquakes with regard to location and depth of focus.

Most earthquakes occur at tectonic plate boundaries. If it's a spreading center or a transform fault (like the San Andreas fault) the earthquake will be shallow-focus. If it's a convergent plate boundary where one plate is subducted under the other, then earthquakes near the plate boundary are shallow focus but as you move away from the plate boundary to where the subducted plate is deeper underground, the earthquakes become more and more deeply focused. See figure 16.22.

Name the three most common sedimentary rocks.

Most sedimentary rocks are detrital sedimentary rocks. The most common detrital rocks, according to table 6.1, are sandstone and shale. The most common chemical sedimentary rock is limestone.

Consider the eruption of Mount Merapi, described at the beginning of this chapter and shown in figure 4.1 . What kind of volcano is Merapi? What evidence did you use to determine this? Based upon your answer, what do you think the plate tectonic setting is of Mount Merapi? What composition of lava do you think it mostly erupts?

Mount Merapi is a composite volcano, as described in section "Types of Volcanoes", subsection "Composite Volcanoes". We know this because it produced pyroclastic flows. Most composite volcanoes are located near convergent plate boundaries, where one plate dives underneath the other. And in fact, figure 1.8 confirms this: Mount Merapi is near the boundary between the Eurasian plate and the Indian-Australian plate. It's near the center of the island of Java. Composite volcanoes erupt mostly felsic lava, with a high proportion of silicates. It erupted again in January of 2021.

What do mud cracks tell us about the environment of deposition of a sedimentary rock?

Mud cracks are illustrated in figure 6.30A on page 148. In figure 6.30B we see lithified mud cracks that have been transformed into shale. On the previous page it is explained that mud cracks are formed in very fine-grained sediment as it dries. In order to dry, they must be exposed above water.They may form in lake-bottom sediment as it dries up, in flood-deposited sediment as the river level drops, or or in marine sediment exposed to air.

2. What would happen, according to Bowen's reaction series, under the following circumstances: olivine crystals form and only the surface of each crystal reacts with the melt to form a coating of pyroxene that prevents the interior of olivine from reacting with the melt?

Multiple layers would form, like the rock that I showed you in class: it had olivine on the bottom, then pyroxene, then amphibole, then biotite, then quartz (amethyst).

How does a natural levee form?

Natural levees form during floods when the river or stream overflows its channel. Water outside the channel flows more slowly because it's shallower, and so it deposits more sediment. This is illustrated in figure 10.25.

What facts make it probable that Earth's core is composed of a mixture of iron and nickel?

Newton's law of gravity shows that the average density of the Earth is 5.5 grams per cubic centimeter. The crustal and mantle rocks are much lighter than this. In order to average out to 5.5 g/cm3 the rocks in the core have to have an average density close to the density of iron. Of course there are lots of combinations of rocks that average out to the density of iron, but about ten percent of meteorites are composed of iron mixed with a small amount of nickel and the other 90% are ultramafic rocks, similar to the Earth's mantle. If we assume that the bodies in the inner solar system are all made of the same materials then iron mixed with nickel seems to be the most likely candidate for the Eart's core.

What are the three main components of magma? What factors control the viscosity of magma?

Note that in chapter 3, section "Igneous Rocks", paragraph 1, "lava" is defined as magma on the earth's surface. There it is noted that magma contains dissolved gases. And in chapter 4, section "Eruptive Violence and Physical Characteristics of Lava", paragraph 2, it is stated that lava is a mixture molten silicate rock, crystals, and gas. It is also stated that "the three factors that influence the viscosity of lava are (1) the silica (SiO2) content of the lava; (2) the temperature of the lava; and (3) the amount of gas dissolved in the magma".

What are the eight most abundant elements in the Earth's crust? Table 2.1 gives the formulas for the most common minerals in the Earth's crust. How do these relate to the eight most abundant elements in the Earth's crust?

O, Si, Al, Fe, Ca, Na, K, Mg. (See box 2.3.) All of the elements included in the top part of table 2.1 are on this list except hydrogen.

What are two reasons why parts of the southwestern United States have an arid climate?

One reason is that it's close to 30° north latitude. Another is that it's in the "rain shadow" cast by the Pacific coast ranges.

How does oxygen in the atmosphere differ from oxygen in rocks and minerals?

Oxygen atoms in the atmosphere are bonded with other oxygen atoms (O2 or O3) or with carbon atoms (CO2).

Why is ozone at the surface considered harmful and ozone in the stratosphere considered beneficial?

Ozone is a more powerful oxidant than ordinary oxygen. If you inhale it it can cause coughing and lung congestion. On the other hand, ozone in the upper atmosphere protects us from ultraviolet radiation.

Name and describe the various types of seismic waves.

P waves: longitudinal body waves. S waves: transverse body waves. Love waves: transverse surface waves, with the ground moving side-to-side. Rayleigh waves: elliptical surface waves that cause the ground to "roll".

What is Pangaea?

Pangea is the name given by Wegener to the ancient supercontinent that eventually split up into today's continents.

What do pillow structures indicate about the environment of volcanism?

Pillow structures indicate that the eruption took place underwater. See figures 4.10 and 4.11 for photographs of pillow lava.

Define polar wandering. What is the paleoclimatic evidence for polar wandering? What is the magnetic evidence for polar wandering? Does polar wandering require the poles to move?

Polar wandering is the apparent motion of the north and south poles. In Wegener's time this could be interpreted as actual movement of the poles, or as evidence that the continents had moved. The magnetic evidence for polar wandering has two forms: first of all, the angle of magnetic dip of ancient rocks is not always consistent with their present latitude, and second, the magnetic field embedded in these rocks does not always point to the current location of the north pole.

Discuss the difference between porosity and permeability.

Porosity is the ability of a rock or sediment layer to hold water. For example, a layer like this would have high porosity: If the white spheres are all sediment particles and the blue background is water, then the porosity here is 0.48, or 48%. (If the spheres are arranged hexagonally then the porosity is 26%.) Permeability is the ability to conduct groundwater. It depends on how interconnected the spaces are within the aquifer.

How does the age of seafloor rocks compare with the age of continental rocks? Be specific.

Rocks on the seafloor are youngest at the spreading centers and become older as you get farther away. The oldest rocks in the seafloor are about 200 million years old. Continental rocks can be as old as four billion years.

Draw a simple geologic map using strike and dip symbols for a syncline plunging to the west.

See Chapter 15 Study Questions

Draw a sketch of an anticline and label the limbs, axial plane, and hinge line.

See Chapter 15 Study Questions

On a geologic map, if no cross-sections were available, how could you distinguish an anticline from a syncline?

See Chapter 15 Study Questions

Sketch and describe the different types of folds, and explain how the shape and orientation of folds is used to interpret strain.

See Chapter 15 Study Questions

How has the study of fracture zones tested the concept of plate motion?

See Chapter 19 Study Questions

List the detrital sediment particles in order of decreasing grain size.

See Chapter 6 Study Questions

How might graded bedding be used to determine the tops and bottoms of sedimentary rock layers in an area where sedimentary rock is no longer horizontal? What other sedimentary structures can be used to determine the tops and bottoms of tilted beds?

See Chapter 6 Study Questions The graded bedding was originally laid down with the larger particles on the bottom, as on the left. The fact that they're on the top here means that the layers have been inverted by tectonic forces. This will be discussed in more detail in chapter 20. Figure 20.17 shows how rock layers can be inverted. The other two figures on the left show mud cracks, which open upward when they are formed, and current ripples.

How much of the 238 U originally part of Earth is still present?

See Chapter 8 Study Questions

Suppose a sequence of sedimentary rock layers was tilted into a vertical position by tectonic forces. How might you determine (a) which end was originally up and (b) the relative ages of the layers?

See Chapter 8 Study Questions

Using information from box 8.4, calculate the age of a feldspar. At present, there are 1.2 million atoms of 40 K. The amount of 40 Ar in the mineral indicates that originally, there were 1.9 million 40 K atoms in the rock. Use a half-life of 1.3 billion years. (Hint: The answer is 862 million years.)

See Chapter 8 Study Questions

Why would you not be able to use the principle of superposition to determine the age of a sill (defined in chapter 3)?

See Chapter 8 Study Questions

Draw diagrams similar to figure 9.1 to compare the shear force to the force of gravity for the following situations: a. a vertical cliff b. a flat horizontal plane c. a 45-degree slope

See Chapter 9 Study Questions

Describe the differences between the continuous and the discontinuous branches of Bowen's reaction series.

See Figure 3.15. The discontinuous branch is on the left, the continuous branch is on the right. Quartz and potassium feldspar belong to both branches.

Sketch a cross section of a fringing reef, a barrier reef, and an atoll.

See figure 18.21 A, B and C.

How does seafloor spreading account for the age of the sea floor?

See figure 19.17. The youngest rocks are at the spreading centers, while the other rocks form progressively older parallel bands. New seafloor is being created at the spreading centers.

How do the crystal structures of pyroxenes and amphiboles differ from one another? Which physical property is used to distinguish between them?

See question 3 above. Pyroxene is a single chain silicate and amphibole is a double chain. According to appendix A in our textbook, pyroxene has 90° cleavage and amphibole has 60° cleavage.

Show in a sketch how longshore drift of sand can form a baymouth bar. In which direction is the longshore drift of sand moving in figure 14.10B? Why?

See the Chapter 14 Study Questions

Show in a sketch the refraction of waves approaching a straight coast at an angle. Explain why refraction occurs.

See the Chapter 14 Study Questions

In a sketch, show the association between an oceanic trench, a Benioff zone of earthquakes, and volcanoes on the edge of a continent.

See the Chapter 18 Study Questions

What is a fracture zone? Sketch the relation between fracture zones and the mid-oceanic ridge.

See the Chapter 18 Study Questions

By applying the various principles, draw a cross section of an area in which the following sequence of events occurred. The relative time relationship for all events should be clear from your single cross section that shows what the geology looks like at present. a. Metamorphism took place during the Archean. During later Precambrian time, uplift and erosion reduced the area to a plane. b. Three layers of marine sedimentary rock were deposited on the plain during Ordovician through Devonian time. c. Although sedimentation may have taken place during the Mississippian through Permian, there are currently no sedimentary rocks of that age in the area. d. A vertical dike intruded all rocks that existed here during the Permian. e. A layer of sandstone was deposited during the Triassic. f. All of the rocks were tilted 45 degrees during the early Cretaceous. This was followed by erosion to a planar surface. g. The area dropped below sea level, and two layers of sedimentary rock were deposited on the erosion surface during the Paleogene and Neogene. h. Uplift and erosion during the Quaternary resulted in a slightly hilly surface. i. Following erosion, a vertical dike fed a small volcano.

See the Chapter 8 Study Questions

Radioactive isotope X decays to daughter isotope Y with a halflife of 220,000 years. At present you have 1/4 gram of X in a rock. From the amount of daughter isotope Y currently in the rock, you determine that the rock contained 16 grams of isotope X when it formed. How many half-lives have gone by? How old is the rock?

Six half-lives have gone by: you originally had 16 grams, then 8, then 4, then 2, then 1, then ½, then ¼. Since each half-life is 220,000 years the age of the rock is 6×220,000 = 1,320,000 years.

Plate tectonics helps cool Earth as hot mantle rock rises near the surface at ridge crests and mantle plumes. What can we assume about the internal temperature of other planets that do not seem to have plate tectonics? What would happen to Earth's internal temperature if the plates stopped moving?

Smaller planets cool faster, so they would not necessarily have hotter interiors than the Earth. However, the absence of plate tectonics means that the interior of the planet is hotter than it would be if there were tectonic activity. If the Earth's tectonic plates stopped moving the interior of the Earth would heat up; but this increase in heat might start them moving again. The driving force behind plate tectonics is convection, which in turn is driven by differences in temperature.

Why is solifluction more common in colder climates than in temperate climates?

Solifluction in cold climates results from the melting of the top layer of permafrost.

Is ice within a glacier a mineral? Is a glacier a rock?

Technically ice within a glacier is considered a mineral. Recall the definition from chapter 2, section "Minerals and Rocks": A mineral is a naturally occurring, inorganic, crystalline solid that has a specific chemical composition. Glacial ice satisfies all of these conditions. Likewise a glacier satisfies the definition of "rock" presented in chapter 2, section "The Rock Cycle".

What is the difference between strike, direction of dip, and angle of dip?

The "strike" is the intersection of the rock layer with an imaginary horizontal plane. The "direction of dip" can be determined by digging down to the rock layer from various points on the surface, and recording the depth. The direction in which the depth increases most rapidly is the "direction of dip". In the example given in my lecture notes, the equation of the strike line was y = 2.5x - 0.5 so the slope is 2.5. Therefore the angle between the strike line and the +x axis is tan-1(2.5) = 68° and the angle between the dip line and the +x axis is 68° - 90° = -22°. So if "up" is north then the direction of dip is 22° south of east: The "angle of dip" is the angle at which the rock layer plunges downward if you travel along the direction of dip. In the example I gave in the lecture notes this was 61°:

What is the Mohorovi˘ci´c discontinuity?

The Mohorovičić discontinuity is the boundary between the crust and the mantle.

Why is it not surprising that the Moon lacks folded mountain ranges like we have on Earth?

The Moon is smaller than the Earth, so it cooled off more rapidly. As a result there has been no tectonic activity on the Moon. So there wouldn't be any folded mountain ranges. On Mars there appears to have been tectonic activity in the past but this ceased billions of years ago.

Most earthquakes occur at plate boundaries where plates interact with each other. How might earthquakes be caused in the interior of a rigid plate?

The New Madrid, Missouri earthquakes of 1811-1812 occurred along an old tectonic plate boundary that was formed 750 million years ago when the supercontinent Rodinia began to break up. Although it is largely inactive, earthquakes still occasionally occur along this fault line. Earthquakes can also occur near volcanoes that are associated with mantle plumes.

Discuss seismic-wave shadow zones and what they indicate about Earth's interior

The S wave shadow zone, illustrated in figure 17.10, shows that the Earth has a liquid outer core which does not permit transverse to pass through. The P wave shadow zone is more complicated. It results from the refraction of waves in the core and mantle. This is illustrated in figure 17.9. The waves that go through the core all emerge at an angle greater than 142° from the epicenter and the waves that don't go through the core emerge at less than 103°.

On examining a basaltic lava flow in Hawaii, you discover that close to the vent, the lava flow has a pahoehoe texture, but further from the vent, it becomes an a 9 a flow. What can explain this?

The a'a flow is more viscous because the lava cooled as it traveled farther from the vent. See factor (2) in the previous question.

Describe the differences between continental crust and oceanic crust.

The characteristics of oceanic crust and continental crust are listed in table 17.1. Oceanic crust is about 7 km thick. Continental crust is 30 to 50 km thick (thickest under mountains). Seismic P waves travel at about 7 km/second in the oceanic crust, and only about 6 km/second in the continental crust. The density of oceanic crust is 3.0 g/cm3 while the density of continental crust is only 2.7 g/cm3. Oceanic crust consists of basalt underlain by gabbro. Continental crust contains more felsic rocks such as granite, schist and gneiss. The upper layers are usually sedimentary.

Describe in detail how earthquake epicenters are located by seismograph stations.

The distance to the epicenter is determined by the time delay between the P wave and the S wave. Once we know the distance we can locate the epicenter on a circle whose radius is the known distance. With two seismic stations we have two circles with the epicenter lying on one of the intersections: With a third seismograph you can eliminate one of the choices:

How does the glacial budget control the migration of the equilibrium line?

The equilibrium line is the place where the rate at which snow falls on a glacier is equal to the rate at which it melts. Below the equilibrium line there is no firn, which is why it is sometimes called the :firn line" or "firn limit". However the glacier extends below this line because of plastic flow. When there is more snowfall the equilibrium line moves downward; when there is less it moves upward.

Explain why a geologist trying to date Devonian volcanic rocks would be more likely to use the potassium-argon system than radiocarbon dating.

The half-life of carbon-14 is 5730 years. (See table 8.3.) The Devonian period ended 359 million years ago. (See figure 8.24.) Divide 359 million by 5730 and you get. 62,600 half-lives. Each time a half-life elapses the amount of carbon-14 is reduced by half. So after 62,600 half-lives the amount of carbon-14 would be the original amount times one-half to the power 62,600. This is such a tiny number that there wouldn't even be one atom left. So you couldn't use carbon-14 to date Devonian rocks.

What happens to the atoms in water when it freezes? Is ice a mineral? Is a glacier a rock?

The hydrogen atoms in a water molecule have a slight positive charge, while the oxygen atom has a slight negative charge. When water freezes the molecules bond together in a hexagonal lattice, with the hydrogen atoms of each molecule being attracted to the oxygen atoms of neighboring molecules. Ice is a mineral and a glacier is a rock.

What happens to originally horizontal layers of sedimentary rock when they are subjected to the deformation associated with regional metamorphism?

The layers become tilted, and in some cases inverted. This kind of tilting occurrerd in north central Wisconsin 1.85 billion years ago when the Superior and Marshfield microcontinents collided, and in the Baraboo area 1.65 billion years ago. The Baraboo event, which produced a layer of quartzite, seems to have been due to a collision with "Continent X", about which little is known.

What factors control a stream's velocity?

The main factor is "gradient", the number of feet per mile that the stream descends. Besides gradient, the stream velocity also depends on the size and shape of the streambed, and on the roughness of the channel.

How does a meander neck cutoff form an oxbow lake?

The outside of a meander tends to erode while the inside deposits more sediment, causing the meander to become more and more exaggerated. This is illustrated in figure 10.21. When the meander closes back on itself, the water "short circuits" and cuts off the meander.

What are some of the technical difficulties you would expect to encounter if you tried to drill a hole to the center of the Earth?

The pressure at the center of the Earth is about 3.6 million atmospheres and the temperature is about 5200°C.

Why do stone buildings tend to weather more rapidly in cities than in rural areas?

The rain in cities is more acidic than in the country, due to the higher concentration of carbon dioxide and other pollutants.

Describe any difference between the amounts of water that would percolate downward to the saturated zone beneath a flat meadow in northern New York and a rocky hillside in southern Nevada. Discuss the factors that control the amount of percolation in each case.

The rate of percolation is controlled by the permeability of the material that the water is percolating through. On the other hand, the amount of water that actually reaches the water table depends on the slope of the land. A flat meadow would eventually absorb all the rainwater landing on it, but it would take a while to reach the subsoil. On a rocky hillside much of the water would run off but the water that did sink in would reach the subsoil and bedrock more quickly.

The amount of water vapor in the atmosphere ranges from 0 to 4%. You experience this as relative humidity, which can range from 0 to 100%. What is the difference between the absolute amount of water in the atmosphere and relative humidity?

The relative humidity is the water vapor in the atmosphere as a percentage of the amopunt that would cause rain or snow. So if the relative humidity is 100% then it's going to start raining. The relative humidity increases as the temperature goes down, even if the actual amount of water vapor stays the same. This is because cold air holds less water than warm air.

Why does the pattern of magnetic anomalies at sea match the pattern of magnetic reversals (recorded in lava flows on land)?

The seafloor spreads at a fairly uniform rate, so the distance that the seafloor travels during one magnetic epoch is proportional to the time that the magnetic field was pointing in that direction. Thus, the widths of the magnetic bands correlate with the lengths of time that the Earth's magnetic field was pointing a particular way.

What is the approximate shape of the solar system?

The solar system is approximately disc-shaped. The planet whose orbit has the greatest inclination is Mercury, which has an orbital inclination of about 7°. Asteroid orbits are also in the same plane, but comets can have orbits that are inclined at large angles. Table 23.2 on p. 570 has the orbital properties of all the planets.

Describe the two main types of seafloor sediment.

The two main types of seafloor sediment are terrigenous sediment and pelagic sediment. Terrigenous sediment comes from the land (mostly river sediment) and pelagic sediment settles down through the ocean water.

What controls the velocity of groundwater flow?

The velocity of groundwater flow is controlled by two things: elevation and pressure. Groundwater flows from higher to lower elevation, just like surface water. It also flows from higher to lower pressure, just like wind blowing from higher to lower air pressure. If the elevation and pressure are both changing, the overall effect is determined by Darcy's law.

What happens to the water table near a pumped well?

The water table descends when water is pumped out of the reservoir. For example, if wells were drilled in the area around Greenbush Kettle, the surface of the lake would descend, since it represents the intersection between the water table and the land surface.

Why do scientists believe there was once liquid water on the surface of Mars?

There are channels on Mars that look as though they were formed by flowing water: Kasei Valles, seen in MOLA elevation data. Flow was from bottom left to right. North is up. Image is approx. 1,600 km (990 mi) across. The channel system extends another 1,200 km (750 mi) south of this image to Echus Chasma. (from Wikipedia) But the main evidence consists of layered rocks recovered by Mars rovers. These resemble the sedimentary rock layers that we have here on Earth. Today there isn't any liquid water on the Martian surface because the atmospheric pressure is so low that it evaporates instantly.

Why are there no active volcanoes in the eastern parts of the United States and Canada?

There are no active volcanoes in the eastern United States because the nearest plate boundary is thousands of miles away and there are no "hot spots", or mantle plumes, nearby.

You find an igneous rock that has large crystals of plagioclase feldspar held within a fine-grained groundmass that is medium gray in color. What kind of rock is it likely to be? What is the name for this texture, and what does it tell you about how the rock formed?

This appears to be a porphyritic rock. This is explained in the textbook in the section "Igneous Rocks", subsection "Igneous Rock Textures", paragraph 5 under "Crystalline Textures". It is believed that porphyries began crystallizing slowly underground and then suddenly erupted to the surface.

Why are some minerals stable several kilometers underground but unstable at Earth's surface?

This is because the pressure is greater at greater depths. It's analogous to how water boils at a lower temperature when you're at a higher altitude, because of the reduced pressure. The bonds are more easily broken when there is less force.

How does dolomite usually form?

This is described in the section "Chemical Sedimentary Rocks", subsection "Carbonite Rocks", under the heading "Dolomite". The most commonly accepted theory is that it forms when magnesium ions replace some of the calcium ions in calcite.

Describe the different processes that could lead to a mafic magma evolving into an intermediate magma.

This is described in the section "How Magmas of Different Compositions Evolve", subsection "Differentiation". The more mafic crystals will settle out of the melt more quickly, thereby leaving behind a more felsic magma. Other processes that can change the composition of magma are described in the following subsections, "Partial Melting" "Assimilation" and "Magma Mixing".

Contrast the geologic conditions responsible for the formation of coal, oil, and natural gas.

This is described on page 536. Coal is formed from decaying plant matter, mostly from coastal swamps. The plant absorbs carbon dioxide and solar energy. The energy is stored in hydrocarbons. When the plant dies its energy is usually released back into the atmosphere, but if it falls into stagnant, oxygen- depleted water and becomes buried by sediment then the energy remains with the plant material. As more sediment accumulates above the plant material the pressure increases and it gradually turns into coal. There are several stages in the formation of coal, as illustrated in table 22.1, page 536. Peat, lignite, subbituminous coal, bituminous coal and anthracite have progressively higher concentrations of energy. Oil is formed under somewhat different conditions. It originates as marine lifeforms in shallow seawater or tropical lagoons. When the lifeforms die they usually oxidize and release their energy, but if they are rapidly buried in sand and mud then they turn into a hydrocarbon-rich sediment called "sapropel". When the sapropel is buried it heats up, at a rate of 25°C for every thousand meters. At 50°C to 100°C it forms oil. Between 100°C and 200°C it forms natural gas. Above 200°C the hydrocarbons break down completely.

Why do mafic magmas tend to reach the surface much more often than felsic magmas?

This is explained in the section "Intrusive Bodies", subsection "Intrusives that Crystallize at Depth", paragraph 4. Felsic magma (which is higher in silica content) is more viscous than mafic magma.

What roles do gases and viscosity play in the generation of explosive eruptions?

This is explained in the section "The Eruptive Products of Volcanoes" subsection "Explosive Eruptions", paragraph 1. They make an analogy with opening a bottle of soda. The gases expand when the pressure is released. If the lava is viscous then it will tend to explode rather than produce bubbles.

What are the relationships among the mantle, the crust, the asthenosphere, and the lithosphere?

This is illustrated in figure 1.7 of the textbook

Describe how waves can straighten an irregular coastline.

This is illustrated in figure 14.13. Due to the lens effect the waves are bent, or "refracted", toward the headland, causing it to erode more rapidly.

What is a turbidity current? What is the evidence that turbidity currents occur on the sea floor?

Turbidity currents are masses of sediment-laden water that are pulled downhill by gravity. The best evidence for the existence of turbidity currents comes from the breaking of underwater cables after earthquakes. If the earthquake itself broke the cable then the break would happen at the same time as the earthquake, but what actually happens is that the cables break in succession from shallower to deeper water, indicating the direction of flow of the current.

If driven 12,000 miles per year, how many more gallons of gasoline per year does a sport utility vehicle or pickup truck rated at 12 miles per gallon use than a minicompact car rated at 52 mpg? Over five years, how much more does it cost to buy gasoline at $4 per gallon for the low-mileage car? At $8 per gallon (the price in many European countries)?

Utility vehicle: 12,000 miles per year divided by 12 miles per gallon is 1000 gallons per year. Minicompact car: 12,000 miles per year divided by 52 miles per gallon is 231 gallons per year. The difference is 769 gallons per year. At $4 per gallon this is 769×4 = $3076 per year, or $15,400 over five years. At $8 per gallon it's twice this, or $30,800.

Why is the surface of Venus hotter than the surface of Mercury, despite Mercury being closer to the Sun?

Venus has a much thicker atmosphere than Mercury, which creates a large greenhouse effect, as described in chapter 21. On Mercury there is almost no atmosphere, so the side that faces the sun is very hot (about 430°C) and the side away from the sun is very cold (about -173°). Venus' surface temperature is about 480°C.

Discuss the origin of marine magnetic anomalies according to Vine and Matthews.

Vine and Matthews were the first to point out that the pattern of seafloor magnetic anomalies was symmetric on both sides of the mid-Atlantic ridge and that it matched the patterns of seafloor anomalies that were found in other oceans. Then they showed that the widths of the seafloor bands correlated with the times between magnetic reversals as recorded in continental rock formations. This combined with Hess's theory of seafloor spreading, which had just been published, to explain the origin of the magnetic bands

How can volcanism occur on small bodies like Io or Enceladus?

Volcanism on Enceladus (a moon of Saturn) and Io (a moon of Jupiter) is probably due to the heating of the moon's interior by tidal flexing. These moons have eccentric orbits that cause their distance from the planet to vary, leading to significant changes in the inverse-cube tidal force.

How do features caused by stream erosion differ from features caused by glacial erosion?

Water is not rigid like ice and flows more easily around curves. Flowing water produces meanders, braided streams, and deltas. Alpine glaciers produce horns, arêtes, tarns (glacial lakes) and hanging valleys.

What tectonic plate are you currently on? Where is the nearest plate boundary, and what kind of boundary is it?

We are on the North American Plate. The nearest plate boundary is the Mid-Atlantic Ridge. It is a divergent boundary.

Summarize Wegener's evidence for continental drift.

Wegener referred to the similarity in coastlines on both sides of the Atlantic, but also found correlations in fossils from various continents. The fact that the continents had drifted was indicated by the fact that evidence of ancient deserts, glaciers and coral reefs was found in places that would not have suitable climates today.

Describe how seismic reflection and seismic refraction show the presence of layers within Earth

When a wave travels from a medium where the wave speed is faster to a region where the wave speed is slower, some of the wave energy is reflected and some is refracted (bent). This is is how a lens works: light travels more slowly in the glass than in the air so it is bent as it enters the glass: When the wave travels from a slower medium to a faster medium it bends the opposite way. If the change in speed is abrupt then a certain amount of the energy is reflected. That's why you can see your reflection in a glass window or lens. The greater the difference in wave speeds, the greater the amount of reflection. The presence of different layers within the Earth is revealed by the fact that seismic waves are reflected and refracted when the different layers transmit waves at different speeds.

What has led to the inner planets having iron cores?

When the planet first from smaller particles the loss in gravitational potential energy translated into a gain in heat energy. This caused the planet to melt, and the heavier elements such as iron sank to the center. Of course there are heavier elements than iron, but they are relatively rare. Iron is the end product of nuclear fusion in stars, whereas the heavier elements are formed at the instant of a supernova explosion, or as a result of a collision between neutron stars. So the core consists mostly of iron.

If you locate a dip-slip fault while doing field work, what kind of evidence would you look for to determine whether the fault is normal or reverse?

You look at corresponding rock layers on opposite sides of the fault. If the rock layers in the hanging wall have moved downward relative to the footwall then it's a normal fault. If they've moved upward relative to the footwall then it's a reverse fault. Reverse faults are usually due to compressional forces. Here's the diagram of the St. Croix horst from the lecture notes: Notice that the green layer in the middle section is higher than the green layer in the side sections and the yellow layer in the middle section is above the yellow layer in the side sections. The middle section has the "hanging walls" because they ride on top of the "footwalls" in the side sections. So the St. Croix horst has reverse faults on both sides.

On Mohs' hardness scale, a fingernail has a hardness of about a. 2-3. b. 3-4. c. 5-6. d. 7-8.

a. 2-3.

The mountain belt that forms the eastern part of North America is called the a. Appalachians. b. North American Cordillera. c. Himalaya. d. Andes. e. Rockies.

a. Appalachians.

How can landslides be prevented during construction? (Choose all that apply.) a. Build retaining walls. b. Cut steeper slopes. c. Install water drainage systems. d. Add vegetation.

a. Build retaining walls. c. Install water drainage systems. d. Add vegetation.

Why would it be difficult to land a spacecraft on Jupiter? a. Jupiter has no solid surface. b. Jupiter's immense gravity would squash it. c. Jupiter's intense magnetic field would destroy it. d. The clouds are so thick it would be hard to navigate to a safe spot

a. Jupiter has no solid surface.

How would you distinguish the following minerals on the basis of physical properties? (You might refer to appendix A.) olivine/pyroxene calcite/quartz mica/halite amphibole/hematite

a. Olivine has no cleavage; pyroxene has two fair cleavage directions at 90° to each other. b. Calcite has three excellent cleavage directions, not at right angles. Quartz has no cleavage. c. Mica has 1 perfect cleavage direction (splits easily into flexible sheets). Halite has 3 excellent cleavage directions at right angles to each other. d. Hematite has a red-brown streak.

Which of these is not part of the definition of a mineral? a. Organic b. Crystalline c. Specific chemical composition d. Naturally occurring

a. Organic

A contact between parallel sedimentary rock layers that records missing geologic time is a. a disconformity. b. an angular unconformity. c. a nonconformity. d. a sedimentary contact.

a. a disconformity.

A glacial valley drowned by rising sea level is a. a fiord. b. an estuary. c. a tombolo. d. a headland.

a. a fiord.

The "Year Without a Summer" in the 1800s was caused by: a. a large volcanic eruption. b. a period of very low sunspot activity. c. a decrease in the concentration of greenhouse gases in the atmosphere. d. greater global albedo due to heavy cloud cover in the Northern Hemisphere.

a. a large volcanic eruption.

The concept of isostacy suggests that higher-elevation mountain ranges are underlain by a. a thick root of continental crust. b. dense oceanic crust. c. a shallow root of continental crust. d. a complex of normal faults.

a. a thick root of continental crust.

Cobbles are more likely to be transported in a stream's a. bed load. b. suspended load. c. dissolved load. d. all of the preceding.

a. bed load.

13. The decomposition of rock from exposure to water and atmospheric gases is called a. chemical weathering. b. transportation. c. deposition. d. mechanical weathering.

a. chemical weathering.

Refer to the periodic table of the elements in appendix D and answer the following questions: a. Which element has an atomic number of 24? b. How many neutrons does it have? c. How many electrons does a neutral atom of this element have?

a. chromium b. 28 c. 24

P waves are a. compressional. b. transverse. c. tensional.

a. compressional.

Folds and reverse faults in a mountain belt suggest a. crustal shortening. b. tensional stress. c. deep-water deposition of the sediment. d. all of the preceding

a. crustal shortening.

In a graded bed, the particle size a. decreases upward. b. decreases downward. c. increases in the direction of the current.

a. decreases upward.

A zone of shallow earthquakes along normal faults is typical of a. divergent boundaries. b. transform boundaries. c. subduction zones. d. collisional boundaries.

a. divergent boundaries.

Passive continental margins are created at a. divergent plate boundaries. b. transform faults. c. convergent plate boundaries.

a. divergent plate boundaries.

Folds in a rock show that the rock behaved in a _____ way. a. ductile b. elastic c. brittle d. all of the preceding

a. ductile

How fast does the central part of a valley glacier move compared to the sides of the glacier? a. faster b. slower c. at the same rate

a. faster

The point within Earth where seismic waves originate is called the a. focus. b. epicenter. c. fault scarp. d. fold.

a. focus.

The driving force behind all mass wasting processes is a. gravity. b. slope angle. c. type of bedrock material. d. presence of water. e. vegetation.

a. gravity.

A river's velocity is _____ on the outside of a meander curve compared to the inside. a. higher b. equal c. lower

a. higher

The bonding between Cl and Na in halite is a. ionic. b. covalent. c. metallic.

a. ionic.

The largest landslide has taken place a. on the sea floor. b. in the Andes. c. on active volcanoes. d. in the Himalaya.

a. on the sea floor.

A lava flow with a ropy or billowy surface is called a. pahoehoe b. a 9 a c. pillow lava d. lahar e. lava tube

a. pahoehoe

Most earthquakes at divergent plate boundaries are a. shallow focus. b. intermediate focus. c. deep focus. d. all of the preceding.

a. shallow focus.

Flow of water-saturated soil over impermeable material is called a. solifluction. b. flow. c. slide. d. creep.

a. solifluction.

The compass direction of a line formed by the intersection of an inclined plane with a horizontal plane is called a. strike. b. direction of dip. c. angle of dip. d. axis.

a. strike.

Longshore drift is a. the movement of sediment parallel to shore when waves strike the shoreline at an angle. b. a type of rip current. c. a type of tide. d. the movement of waves.

a. the movement of sediment parallel to shore when waves strike the shoreline at an angle.

Porosity is a. the percentage of a rock's volume that is openings. b. the capacity of a rock to transmit a fluid. c. the ability of a sediment to retard water. d. none of the preceding.

a. the percentage of a rock's volume that is openings.

Stream erosion and deposition are controlled primarily by a river's a. velocity. b. discharge. c. gradient. d. channel shape. e. channel roughness.

a. velocity.

Flux melting occurs when a. water is added to the asthenosphere. b. a mantle plume increases the temperature of the asthenosphere. c. mantle material undergoes depression. d. mantle material flows downward to greater depths and higher

a. water is added to the asthenosphere.

The gas most commonly released during a volcanic eruption is a. water vapor. b. carbon dioxide. c. sulfur dioxide. d. hydrogen sulfide.

a. water vapor.

The major difference between intrusive igneous rocks and extrusive igneous rocks is a. where they solidify. b. chemical composition. c. type of minerals. d. all of the preceding.

a. where they solidify.

An astronomical unit (AU) is equivalent to approximately a. 50 million miles. b. 150 million kilometers. c. 100 billion kilometers. d. 250 million miles.

b. 150 million kilometers.

The chemical element found in dolomite not found in limestone is a. Ca. b. Mg. c. C. d. O. e. Al.

b. Mg.

20. Which of the following is not a component of volcanic hazard mitigation? a. Mapping older volcanic deposits b. Preventing a volcanic eruption c. Monitoring earthquake activity around a volcano d. Alerting nearby residents of an imminent eruption

b. Preventing a volcanic eruption

Glacially carved valleys are usually _____ shaped. a. V b. U c. Y

b. U

A broad ramp of sediment formed at the base of mountains when alluvial fans merge is a. a playa. b. a bajada. c. a pediment. d. an arroyo.

b. a bajada.

A platform of sediment formed where a stream flows into standing water is a. an alluvial fan. b. a delta. c. a meander. d. a flood plain.

b. a delta.

The Maunder Minimum or "Little Ice Age" of the late seventeenth century is believed to have been caused by: a. a large volcanic eruption. b. a period of very low sunspot activity. c. a decrease in the concentration of greenhouse gases in the atmosphere. d. greater global albedo due to heavy cloud cover in the Northern Hemisphere.

b. a period of very low sunspot activity. c. a decrease in the concentration of greenhouse

A seismic gap is a. the time between large earthquakes. b. a segment of an active fault where earthquakes have not occurred for a long time. c. the center of a plate where earthquakes rarely happen.

b. a segment of an active fault where earthquakes have not occurred for a long time.

A change in magma composition due to melting of surrounding country rock is called a. magma mixing. b. assimilation. c. differentiation. d. partial melting.

b. assimilation.

Reefs parallel to the shore but separated from it by wide, deep lagoons are called a. fringing reefs. b. barrier reefs. c. atolls. d. lagoonal reefs.

b. barrier reefs.

Mercury's inclined and elliptical orbit is believed to be the result of a. its proximity to the Sun. b. collision with an enormous planetesimal. c. the gravitational pull of Jupiter. d. its very slow rotation.

b. collision with an enormous planetesimal.

19. Which volcano is not usually made of basalt? a. shield b. composite cone c. spatter cone d. cinder cone

b. composite cone

What type of plate boundary is most commonly associated with mountain building? a. divergent b. convergent c. transform

b. convergent

Thick accumulations of graywacke and volcanic sediments can indicate an ancient a. divergent plate boundary. b. convergent boundary. c. transform boundary.

b. convergent boundary.

A discordant shallow intrusive structure is called a a. stock. b. dike. c. sill. d. laccolith.

b. dike.

In a normal fault, the hanging-wall block has moved _____ relative to the footwall block. a. upward b. downward c. sideways

b. downward

A substance that cannot be broken down into other substances by ordinary chemical methods is a(n) a. crystal. b. element. c. molecule. d. acid.

b. element.

Periods are subdivided into a. eras. b. epochs. c. ages. d. time zones.

b. epochs.

The boundary between the zone of accumulation and the zone of ablation of a glacier is called the a. firn. b. equilibrium line. c. ablation zone. d. moraine.

b. equilibrium line.

Fractures in bedrock along which movement has taken place are called a. joints. b. faults. c. cracks. d. folds.

b. faults.

Groundwater flows a. always downhill. b. from areas of high hydraulic head to low hydraulic head. c. from high elevation to low elevation. d. from high permeability to low permeability. 22. The drop in the water table around a pumped well is

b. from areas of high hydraulic head to low hydraulic head.

The most common igneous rock of the continents is a. basalt. b. granite. c. rhyolite. d. peridotite.

b. granite.

Which of the following is not true of tsunami? a. very long wavelength b. high wave height in deep water c. very fast moving d. continued flooding after wave crest hits shore

b. high wave height in deep water

Atoms with either a positive or a negative charge are called a. compounds. b. ions. c. elements. d. isotopes.

b. ions.

The principle of continents being in a buoyant equilibrium is called a. subsidence. b. isostasy. c. convection. d. rebound.

b. isostasy.

Which of the following is not an example of the effects of isostasy? a. deep mountain roots b. magnetic reversals c. the postglacial rise of northeastern North America d. mountain ranges at subduction zones

b. magnetic reversals

The Richter scale measures a. intensity. b. magnitude. c. damage and destruction caused by the earthquake. d. the number of people killed by the earthquake.

b. magnitude.

Limestone recrystallizes during metamorphism into a. hornfels. b. marble. c. quartzite. d. schist.

b. marble.

Which of the following energy sources does not directly produce carbon dioxide? a. coal b. nuclear power c. natural gas d. petroleum

b. nuclear power

The path a water particle makes as a wave passes in deep water is best described as a. elliptical. b. orbital. c. spherical. d. linear.

b. orbital.

The continuous branch of Bowen's reaction series contains the mineral a. pyroxene. b. plagioclase. c. amphibole. d. quartz.

b. plagioclase.

The major difference between breccia and conglomerate is a. size of grains. b. rounding of the grains. c. composition of grains. d. all of the preceding.

b. rounding of the grains.

Particles of sediment from 1/16 to 2 millimeters in diameter are of what size? a. gravel b. sand c. silt d. clay

b. sand

Which is not a chemical or organic sedimentary rock? a. rock salt b. sandstone c. limestone d. gypsum

b. sandstone

The Vine-Matthews hypothesis explains the origin of

b. seafloor magnetic anomalies.

The resistance to movement or deformation of soil is its a. mass. b. shear strength. c. shear force. d. density.

b. shear strength.

By definition, stocks differ from batholiths in a. shape. b. size. c. chemical composition. d. age.

b. size.

"Within a sequence of undisturbed sedimentary rocks, the layers get younger going from bottom to top" is the principle of a. original horizontality. b. superposition. c. cross-cutting. d. unconformities.

b. superposition.

13. The easiest method of escaping a rip current is to a. swim toward shore. b. swim parallel to the shore. c. swim away from the shore.

b. swim parallel to the shore.

Permeability is a. the percentage of a rock's volume that is openings. b. the capacity of a rock to transmit a fluid. c. the ability of a sediment to retard water. d. none of the preceding.

b. the capacity of a rock to transmit a fluid.

Rounding is a. the rounding of a grain to a spherical shape. b. the grinding away of sharp edges and corners of rock fragments during transportation. c. a type of mineral. d. none of the preceding.

b. the grinding away of sharp edges and corners of rock fragments during transportation.

In a receding glacier, a. ice flows from lower elevations to higher elevations. b. the terminus moves upvalley. c. the equilibrium line moves to a lower elevation. d. all of the preceding.

b. the terminus moves upvalley.

Normal faults occur where a. there is horizontal shortening. b. there is horizontal extension. c. the hanging wall moves up. d. the footwall moves down.

b. there is horizontal extension.

Volcanic eruptions can affect the climate because a. they heat the atmosphere. b. volcanic dust and gas can reduce the amount of solar radiation that penetrates the atmosphere. c. they change the elevation of the land. d. all of the preceding.

b. volcanic dust and gas can reduce the amount of solar radiation that penetrates the atmosphere.

A typical rate of plate motion is a. 3-4 meters per year. b. 1 kilometer per year. c. 1-10 centimeters per year. d. 1,000 kilometers per year.

c. 1-10 centimeters per year.

What is the minimum number of seismic stations needed to determine the location of the epicenter of an earthquake? a. 1 b. 2 c. 3 d. 5 e. 10

c. 3

Which of these common minerals is not a silicate? a. Quartz b. Feldspar c. Gypsum d. Mica

c. Gypsum

Which of the following is an example of a shield volcano? a. Mount St. Helens, Washington State b. Mount Merapi, Indonesia c. Mauna Loa, Hawaii d. Cerro Negro, Nicaragua

c. Mauna Loa, Hawaii

The boundary that separates the crust from the mantle is called the a. lithosphere. b. asthenosphere. c. Mohorovi˘ci´c discontinuity. d. none of the preceding.

c. Mohorovi˘ci´c discontinuity.

Why is beach sediment typically quartz-rich sand? a. Other minerals are not deposited on beaches. b. Quartz is the only mineral that can be sand-sized. c. Quartz is resistant to chemical weathering. d. None of the preceding

c. Quartz is resistant to chemical weathering.

In a single chain silicate, how many of the oxygen atoms in each silica tetrahedron are shared with neighboring silica tetrahedra? a. None b. One c. Two d. Three e. Four

c. Two

An anticline is a. a fold shaped like an arch with the youngest rocks exposed in the center of the fold. b. a trough-shaped fold with the oldest rocks exposed in the center of the fold. c. a fold shaped like an arch with the oldest rocks exposed in the center of the fold. d. a trough-shaped fold with the youngest rocks exposed in the center of the fold.

c. a fold shaped like an arch with the oldest rocks exposed in the center of the fold.

Coal forms a. by crystal settling. b. through hydrothermal processes. c. by compaction of plant material. d. on the ocean floor.

c. by compaction of plant material.

15. The single most effective agent of chemical weathering at Earth's surface is a. carbonic acid H 2 CO 3 . b. water H 2 O. c. carbon dioxide CO 2 . d. hydrochloric acid HCl.

c. carbon dioxide CO 2 .

What is the slowest type of mass wasting process? a. debris flow b. rockslide c. creep d. rockfall e. avalanche

c. creep

Foliation forms as a result of a. confining pressure. b. lithostatic pressure. c. differential stress. d. contact metamorphism.

c. differential stress.

The subatomic particle that contributes a single negative electrical charge is the a. proton. b. neutron. c. electron.

c. electron.

A descending mass moving downslope as a viscous fluid is referred to as a a. fall. b. landslide. c. flow. d. slide.

c. flow.

Plate tectonics is a result of Earth's internal heat engine, powered by (choose all that apply) a. the magnetic field. b. the Sun. c. gravity. d. heat flowing from Earth's interior outward.

c. gravity. d. heat flowing from Earth's interior outward.

Alpine glaciation a. is a type of glacier. b. exists where a large part of a continent is covered by glacial ice. c. is found in mountainous regions. d. is found only at high latitudes.

c. is found in mountainous regions.

Atoms of an element containing different numbers of neutrons but the same number of protons are called a. ions. b. covalent. c. isotopes. d. neutral.

c. isotopes.

The defining characteristic of a desert is a. shifting sand dunes. b. high temperatures. c. low rainfall. d. all of the preceding. e. none of the preceding.

c. low rainfall.

Crystalline substances are always a. ionically bonded. b. minerals. c. made of repeating patterns of atoms. d. made of glass.

c. made of repeating patterns of atoms.

The Hawaiian Islands are thought to be the result of a. subduction. b. midocean ridge volcanics. c. mantle plumes. d. ocean-ocean convergence.

c. mantle plumes.

Which of the following is a greenhouse gas? a. nitrogen b. oxygen c. methane d. argon

c. methane

If rock A cuts across rock B, then rock B is _____ rock A. a. younger than b. the same age as c. older than

c. older than

A very flat surface underlain by a dry lake bed of hard, mud-cracked clay is called a a. ventifact. b. plateau. c. playa. d. none of the preceding.

c. playa.

Which of the following is not characteristic of a mountain belt that formed through ocean-continent convergence? a. fold and thrust belts b. thick accumulations of marine sediment c. prevalence of normal faults over reverse faults d. metamorphism

c. prevalence of normal faults over reverse faults

Another term for parent rock is a. starter. b. primer. c. protolith. d. sediment.

c. protolith.

14. Quartz sandstone is changed during metamorphism into a. hornfels. b. marble. c. quartzite. d. schist.

c. quartzite

Which is not an intrusive igneous rock? a. gabbro b. diorite c. rhyolite d. peridotite

c. rhyolite

A structure in which the beds dip away from a central point and the oldest rocks are exposed in the center is called a(n) a. basin. b. anticline. c. structural dome. d. syncline.

c. structural dome.

The sliding of oceanic lithosphere beneath a continent or island arc is called a. rotation. b. tension. c. subduction. d. polar wandering.

c. subduction.

Which is not a type of coal? a. lignite b. bituminous c. sulfite d. anthracite

c. sulfite

The lithosphere is a. the same as the crust. b. the layer beneath the crust. c. the crust and uppermost mantle. d. only part of the mantle.

c. the crust and uppermost mantle.

The S-wave shadow zone is evidence that a. the core is made of iron and nickel. b. the inner core is solid. c. the outer core is fluid. d. the mantle behaves as ductile material

c. the outer core is fluid.

The average time between floods of a given size is a. the discharge. b. the gradient. c. the recurrence interval. d. the magnitude.

c. the recurrence interval.

The San Andreas fault in California is a

c. transform fault.

Which of the following is the correct order of the layers of the atmosphere from the ground up? a. stratosphere, mesosphere, troposphere, thermosphere b. thermosphere, troposphere, stratosphere, mesosphere c. troposphere, stratosphere, mesosphere, thermosphere d. stratosphere, troposphere, mesosphere, thermosphere

c. troposphere, stratosphere, mesosphere, thermosphere

Great masses of sediment-laden water that are pulled downhill by gravity are called a. contour currents. b. bottom currents. c. turbidity currents. d. traction currents.

c. turbidity currents.

The discontinuous branch of Bowen's reaction series contains the mineral a. pyroxene. b. amphibole. c. olivine. d. All of the above

d. All of the above

Which is not true of a single silicon-oxygen tetrahedron? a. The atoms of the tetrahedron are strongly bonded together. b. It has a net negative charge. c. The formula is SiO 4 . d. It has four silicon atoms.

d. It has four silicon atoms.

20. The soil horizon containing only organic material is the a. A horizon. b. B horizon. c. C horizon. d. O horizon. e. E horizon.

d. O horizon.

_____ is a rock composed of frothy volcanic glass a. Obsidian b. Basalt c. Tuff d. Pumice

d. Pumice

Why do Mercury and the Moon lack an atmosphere? a. They formed after all the gas had been used up. b. They are so cold that all their gases have frozen into deposits below their surface. c. They formed before the solar nebula had captured any gas. d. They are so small that their gravity is too weak to retain an atmosphere.

d. They are so small that their gravity is too weak to retain an atmosphere.

Which of these is not a type of pyroclastic material? a. ash b. dust c. lapilli d. a ' a e. bomb

d. a ' a

A syncline is a. a fold shaped like an arch with the youngest rocks exposed in the center of the fold. b. a trough-shaped fold with the oldest rocks exposed in the center of the fold. c. a fold shaped like an arch with the oldest rocks exposed in the center of the fold. d. a trough-shaped fold with the youngest rocks exposed in the center of the fold.

d. a trough-shaped fold with the youngest rocks exposed in the center of the fold.

Seismic refraction is caused by a. seismic waves bending. b. a change in velocity of seismic waves. c. sharp rock boundaries. d. all of the above. e. a and b.

d. all of the above.

Which is a source for terranes? a. microcontinents b. fragments of distant continents c. island arcs d. all of the preceding

d. all of the preceding

Which is characteristic of mid-oceanic ridges? a. shallow-focus earthquakes b. high heat flow c. basalt eruptions d. all of the preceding

d. all of the preceding

Which of the following determines how quickly groundwater flows? a. elevation b. water pressure c. permeability d. all of the preceding

d. all of the preceding

Which structures would interfere with longshore drift? a. jetties b. groins c. breakwaters d. all of the preceding

d. all of the preceding

18. An example of a composite volcano is a. Mount Rainier. b. Fujiyama. c. Mount Vesuvius. d. all of the preceding.

d. all of the preceding.

Oceanic and continental crust differ in a. composition. b. density. c. thickness. d. all of the preceding.

d. all of the preceding.

Oceanic trenches a. are narrow, deep troughs. b. run parallel to the edge of a continent or an island arc. c. are often 8 to 10 kilometers deep. d. all of the preceding.

d. all of the preceding.

The ability of a mineral to break along preferred directions is called a. fracture. b. crystal form. c. hardness. d. cleavage.

d. cleavage.

The portion of a continent that has been structurally stable for a prolonged period of time is called a(n) a. orogeny. b. basin. c. mountain belt. d. craton.

d. craton.

The total area drained by a stream and its tributaries is called the a. hydrologic cycle. b. tributary area. c. divide. d. drainage basin.

d. drainage basin.

Which is not a foliated metamorphic rock? a. gneiss b. schist c. phyllite d. hornfels

d. hornfels

The core is probably composed mainly of a. silicon. b. sulfur. c. oxygen. d. iron.

d. iron.

Compaction and cementation are two common processes of a. erosion. b. transportation. c. deposition. d. lithification.

d. lithification.

12. Physical disintegration of rock into smaller pieces is called a. chemical weathering. b. transportation. c. deposition. d. mechanical weathering.

d. mechanical weathering.

Benioff zones are found near a. midocean ridges. b. ancient mountain chains. c. interiors of continents. d. oceanic trenches.

d. oceanic trenches.

14. Which is not a type of mechanical weathering? a. frost wedging. b. frost heaving. c. pressure release. d. oxidation.

d. oxidation.

The major difference between a mesa and a butte is one of a. shape. b. elevation. c. rock type. d. size.

d. size.

The Wilson Cycle describes a. the cycle of uplift and erosion of mountains. b. the movement of asthenosphere. c. the block-faulting that occurs at mountains. d. the cycle of splitting of a supercontinent, opening of an ocean basin, followed by closing of the basin and collision of continents.

d. the cycle of splitting of a supercontinent, opening of an ocean basin, followed by closing of the basin and collision of continents.

Which is not a type of unconformity? a. disconformity b. angular unconformity c. nonconformity d. triconformity

d. triconformity

What would the temperature of the Earth be if there were no atmosphere? a. 15°C b. 545°C c. 0°C d. −19 ° C

d. −19 ° C

Which would characterize an erosional coast? a. headlands b. sea cliffs c. stacks d. arches e. all of the preceding

e. all of the preceding

Which is not a type of dune? a. barchan b. transverse c. parabolic d. longitudinal e. all of the preceding are dunes

e. all of the preceding are dunes

Which would characterize a depositional coast? a. headlands b. sea cliffs c. stacks d. arches e. barrier islands

e. barrier islands

Which is not a drainage pattern? a. dendritic b. radial c. rectangular d. trellis e. none of the preceding

e. none of the preceding

17. The most common end product of the chemical weathering of quartz is a. clay minerals. b. pyroxene. c. amphibole. d. calcite. e. quartz does not usually weather chemically.

e. quartz does not usually weather chemically.

Which of these is not a major type of volcano? a. shield b. cinder cone c. composite d. stratovolcano e. spatter cone

e. spatter cone

Which is not a type of fold? a. open b. isoclinal c. overturned d. recumbent e. thrust

e. thrust

Eras are subdivided into a. periods. b. eons. c. ages. d. epochs.

periods.