Chapter 1 Testing Your Knowledge Use the following questions to prepare for exams based on this chapter. 1. Compare the hazards of lava flows to those of pyroclastic flows. 2. What roles do gases play in volcanism? 3. What do pillow structures indicate about the environment of volcanism? 4. Name the minerals and the approximate percentage of each that you would expect to be present in each of the following rocks: andesite, rhyolite, basalt. 5. What property (or characteristic) of obsidian makes it an exception to the usual geologic definition of rock? 6. What determines the viscosity of a lava? 7. What determines whether a series of volcanic eruptions builds a shield volcano, a composite volcano, or a cinder cone? Describe each type of volcanic cone. 8. Explain how a vesicular porphyritic andesite might have formed. 9. Why are extrusive igneous rocks fine-grained? 10. Why don’t flood basalts build volcanic cones? 11. Mount St. Helens a. last erupted violently in 1980 b. is part of the Cascade Range c. had a revival of dome growing in 2004 d. all of the preceding 12. 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 13. Whether volcanic eruptions are very explosive or relatively quiet is largely determined by a. the amount of gas in the lava or magma b. the ease or difficulty with which the gas escapes to the atmosphere c. the viscosity of a lava d. all of the preceding 14. Temperatures at which lavas solidify range from about ____°C for silicic rocks to ____°C for mafic rocks. a. 100, 200 b. 300, 1,000 c. 700, 1,200 d. 1,000, 2,000 15. One gas typically not released during a volcanic eruption is a. water vapor b. carbon dioxide c. sulfur dioxide d. hydrogen sulfide e. oxygen 16. Mafic rocks contain about ____% silica. a. 10 b. 25 c. 50 d. 65 e. 80 17. Silicic rocks contain about ____% silica. a. 10 b. 25 c. 50 d. 70 e. 80 18. Which is not an extrusive igneous rock? a. granite b. rhyolite c. basalt d. andesite 19. Which is not a major type of volcano? a. shield b. cinder cone c. composite d. stratovolcano e. spatter cone 20. A typical example of a shield volcano is a. Mount St. Helens b. Kilauea in Hawaii c. El Chichón d. Mount Vesuvius 21. An example of a composite volcano is a. Mount Rainier b. Fujiyama c. Mount Vesuvius d. all of the preceding 22. Which volcano is not usually made of basalt? a. shield b. composite cone c. spatter cone d. cinder cone 23. An igneous rock made of pyroclasts has a texture called a. fragmental b. vesicular c. porphyritic d. fine-grained 24. Why do mafic magmas tend to reach the surface much more often than silicic magmas? 25. What role does the asthenosphere play in generating magma at (a) a convergent boundary; (b) a divergent boundary? 26. How do batholiths form? 27. How would you distinguish, on the basis of minerals present, among granite, gabbro, and diorite? 28. How would you distinguish andesite from a diorite? 29. What rock would probably form if magma that was feeding volcanoes above subduction zones solidified at considerable depth? 30. Why is a higher temperature required to form magma at the oceanic ridges than in the continental crust? 31. What is the difference between feldspar found in gabbro and feldspar found in granite? 32. What is the difference between a dike and a sill? 33. Describe the differences between the continuous and the discontinuous branches of Bowen’s reaction series. 34. A surface separating different rock types is called a a. xenolith b. contact c. chill zone d. none of the preceding 35. 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 36. Which is not an intrusive igneous rock? a. gabbro b. diorite c. granite d. andesite 37. By definition, stocks differ from batholiths in a. size b. shape c. chemical composition d. all of the preceding 38. Which is not a source of heat for melting rock? a. geothermal gradient b. the hotter mantle c. mantle plumes d. water under pressure 39. The geothermal gradient is, on the average, about a. 1°C/km b. 10°C/km c. 30°C/km d. 50°C/km 40. The continuous branch of Bowen’s reaction series contains the mineral a. pyroxene b. plagioclase c. amphibole d. biotite 41. The discontinuous branch of Bowen’s reaction series contains the mineral a. pyroxene b. amphibole c. biotite d. all of the preceding 42. The most common igneous rock of the continents is a. basalt b. granite c. rhyolite d. ultramafic 43. Granitic magmas are associated with a. convergent boundaries and magmatic underplating b. divergent boundaries and differentiation c. convergent boundaries and decompression melting d. divergent boundaries and water release 44. The difference in texture between intrusive and extrusive rocks is primarily due to a. different mineralogy b. different rates of cooling and crystallization c. different amounts of water in the magma 45. Mafic magma is generated at divergent boundaries because of a. water under pressure b. decompression melting c. magmatic underplating d. melting of the lithosphere 46. A change in magma composition due to melting of surrounding country rock is called a. magma mixing b. assimilation c. crystal setting d. partial melting 47. Quartz is a common mineral in sandstone. Under certain cir cumstances, feldspar is common in sandstone, even though it normally weathers rapidly to clay. What conditions of climate, weathering rate, and erosion rate could lead to a feldspar-rich sandstone? Explain your answer. 48. Describe with sketches how wet mud compacts before it becomes shale. 49. What do mud cracks tell about the environment of deposition of a sedimentary rock? 50. How does a graded bed form? 51. List the detrital sediment particles in order of decreasing grain size. 52. How does a sedimentary breccia differ in appearance and origin from a conglomerate? 53. Describe three different origins for limestone. 54. How does dolomite usually form? 55. What is the origin of coal? 56. Sketch the cementation of sand to form sandstone. 57. How do evaporites form? Name two evaporites. 58. Name the three most common sedimentary rocks. 59. What is a formation? 60. Explain two ways that cross-bedding can form. 61. Particles of sediment from 1/16 to 2 millimeters in diameter are of what size? a. gravel b. sand c. silt d. clay 62. 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 63. Compaction and cementation are two common processes of a. erosion b. transportation c. deposition d. lithification 64. Which is not a chemical or organic sedimentary rock? a. rock salt b. shale c. limestone d. gypsum 65. 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 66. Which is not a type of sandstone? a. quartz sandstone b. arkose c. graywacke d. coal 67. Shale differs from mudstone in that a. shale has larger grains b. shale is visibly layered and fissile; mudstone is massive and blocky c. shale has smaller grains d. there is no difference between shale and mudstone 68. The chemical element found in dolomite not found in limestone is a. Ca b. Mg c. C d. O e. Al 69. In a graded bed, the particle size a. decreases upward b. decreases downward c. increases in the direction of the current d. stays the same 70. A body or rock of considerable thickness with characteristics that distinguish it from adjacent rock units is called a/an a. formation b. contact c. bedding plane d. outcrop 71. If sea level drops or the land rises, what is likely to occur? a. a flood b. a regression c. a transgression d. no geologic change will take place 72. Thick accumulations of graywacke and volcanic sediments can indicate an ancient a. divergent plate boundary b. convergent boundary c. transform boundary 73. A sedimentary rock made of fragments of preexisting rocks is a. organic b. chemical c. clastic 74. Clues to the nature of the source area of sediment can be found in a. the composition of the sediment b. sedimentary structures c. rounding of sediment d. all of the preceding 75. What are the effects on metamorphic minerals and textures of temperature, confining pressure, and differential stress? 76. What are the various sources of heat for metamorphism? 77. How do regional metamorphic rocks commonly differ in texture from contact metamorphic rocks? 78. Why is such a variety of combinations of pressure and temperature environments possible during metamorphism? 79. How would you distinguish a. schist and gneiss? b. slate and phyllite? c. quartzite and marble? d. granite and gneiss? 80. Why is an edifice built with blocks of quartzite more durable than one built of marble blocks? 81. Which is not regarded as a low-grade metamorphic rock? a. greenschist b. phyllite c. slate d. gneiss 82. Shearing is a type of a. compressive stress b. confining pressure c. lithostatic pressure d. differential stress 83. Metamorphic rocks with a planar texture (the constituents of the rock are parallel to one another) are said to be a. concordant b. foliated c. discordant d. nonfoliated 84. Metamorphic rocks are classified primarily on a. texture—the presence or absence of foliation b. mineralogy—the presence or absence of quartz c. environment of deposition d. chemical composition 85. Which is not a foliated metamorphic rock? a. gneiss b. schist c. quartzite d. slate 86. Limestone recrystallizes during metamorphism into a. hornfels b. marble c. quartzite d. schist 87. Quartz sandstone is changed during metamorphism into a. hornfels b. marble c. quartzite d. schist 88. The correct sequence of rocks that are formed when shale undergoes prograde metamorphism is a. slate, gneiss, schist, phyllite b. phyllite, slate, schist, gneiss c. slate, phyllite, schist, gneiss d. schist, phyllite, slate, gneiss 89. The major difference between metamorphism and metasomatism is a. temperature at which each takes place b. the minerals involved c. the area or region involved d. metasomatism is metamorphism coupled with the introduction of ions from an external source 90. Ore bodies at divergent plate boundaries can be created through a. contact metamorphism b. regional metamorphism c. hydrothermal processes 91. A schist that developed in a high-pressure, low-temperature environment likely formed a. in the lower part of the continental crust b. in a subduction zone c. in a mid-oceanic ridge d. near a contact with a magma body 92. A metamorphic rock that has undergone partial melting to produce a mixed igneous-metamorphic rock is a a. gneiss b. hornfels c. schist d. migmatite Expanding Your Knowledge 1. What might explain the remarkable alignment of the Cascade volcanoes? 2. What would the present-day environmental effects be for an eruption such as that which created Crater Lake? 3. Why are there no active volcanoes in the eastern parts of the United States and Canada? 4. Why are continental igneous rocks richer in silica than oceanic igneous rocks? 5. In parts of major mountain belts there are sequences of rocks that geologists interpret as slices of ancient oceanic lithosphere. Assuming that such a sequence formed at a divergent boundary and was moved toward a convergent boundary by plate motion, what rock types would you expect to make up this sequence, going from the top downward? 6. 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? 7. 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? 8. Which would weather faster in a humid climate, a quartz sandstone or an arkose? Explain your answer. 9. A cross-bedded quartz sandstone may have been deposited as a beach sand or as a dune sand. What features could you look for within the rock to tell if it had been deposited on a beach? On a dune? 10. Why is burial usually necessary to turn a sediment into a sedimentary rock? 11. Why are most beds of sedimentary rock formed horizontally? 12. Discuss the role of sedimentary rocks in the rock cycle, diagramming the rock cycle as part of your answer. What do sedimentary rocks form from? What can they turn into? 13. Should ultramafic rocks in the upper mantle be regarded as metamorphic rocks rather than igneous rocks? 14. Where were the metals before they were concentrated in hydrothermal vein ore deposits? 15. What happens to originally horizontal layers of sedimentary rock when they are subjected to the deformation associated with regional metamorphism? 16. Where in Earth’s crust would you expect most migmatites to form? Chapter 2. Testing Your Knowledge Use the following questions to prepare for exams based on this chapter. 1. Most anticlines have both limbs dipping away from their hinge lines. For which kind of fold is this not the case? 2. What is the difference between a joint and a fault? 3. On a geologic map, if no cross sections were available, how could you distinguish an anticline from a syncline? 4. 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? 5. What factors control whether a rock behaves as a brittle material or a ductile material? 6. What is the difference between strike, direction of dip, and angle of dip? 7. Draw a simple geologic map using strike and dip symbols for a syncline plunging to the west. 8. How does a structural dome differ from a plunging anticline? 9. Which of the statements is true? a. when forces are applied to an object, the object is under stress b. strain is the change in shape or size (volume), or both, while an object is undergoing stress c. stresses can be compressive, tensional, or shear d. all of the preceding 10. 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 11. Folds in a rock show that the rock behaved in a _____ way. a. ductile b. elastic c. brittle d. all of the preceding 12. 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 13. 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 14. A structure in which the beds dip away from a central point and the oldest rocks are exposed in the center is called a a. basin b. anticline c. structural dome d. syncline 15. Which is not a type of fold? a. open b. isoclinal c. overturned d. recumbent e. thrust 16. Fractures in bedrock along which movement has taken place are called a. joints b. faults c. cracks d. folds 17. In a normal fault, the hanging-wall block has moved _____ relative to the footwall block. a. upward b. downward c. sideways 18. Normal faults occur where a. there is horizontal shortening b. there is horizontal extension c. the hanging wall moves up d. where the footwall moves down 19. Faults that typically move older rock on top of younger rock are a. normal faults b. thrust faults c. strike-slip faults 20. 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? 21. Radioactive isotope X decays to daughter isotope Y with a half-life of 120,000 years. At present you have 1/4 gram of X in a rock. From the amount of daughter isotope Y presently in the rock, you determine that the rock contained 8 grams of isotope X when it formed. How many half-lives have gone by? How old is the rock? 22. 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 presently 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° during the early Cretaceous. This was followed by erosion to a planar surface. g. The area dropped below sea level, and two layers of Tertiary sedimentary rock were deposited on the erosion surface. h. Uplift and erosion during the Quaternary resulted in a slightly hilly surface. i. Following erosion, a vertical dike fed a small volcano. 23. Name as many types of contacts (e.g., intrusive contact) as you can. 24. Using figure 8.23, suppose the base of the Hamlinville Formation has a layer of volcanic ash that is dated as being 49 million years old. How old is the Foster City Formation? 25. “Geological processes operating at present are the same processes that have operated in the past” is the principle of a. correlation b. catastrophism c. uniformitarianism d. none of the preceding 26. “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. crosscutting d. none of the preceding 27. If rock A cuts across rock B, then rock A is ____ rock B. a. younger than b. the same age as c. older than 28. Which is a method of correlation? a. physical continuity b. similarity of rock types c. fossils d. all of the preceding 29. Eras are subdivided into a. periods b. eons c. ages d. epochs 30. Periods are subdivided into a. eras b. epochs c. ages d. time zones 31. Which division of geologic time was the longest? a. Precambrian b. Paleozoic c. Mesozoic d. Cenozoic 32. Which is a useful radioactive decay scheme? a. 238U 206Pb b. 235U 207Pb c. 40K 40Ar d. 87Rb 87Sr e. all of the preceding 33. C-14 dating can be used on all of the following except a. wood b. shell c. the Dead Sea Scrolls d. granite e. bone 34. Concentrations of radon are highest in areas where the bedrock is a. granite b. gneiss c. limestone d. black shale e. phosphate-rich rock f. all of the preceding 35. Which is not a type of unconformity? a. disconformity b. angular unconformity c. nonconformity d. triconformity 36. A geologist could use the principle of inclusion to determine the relative age of a. fossils b. metamorphism c. shale layers d. xenoliths 37. The oldest abundant fossils of complex multicellular life with shells and other hard parts date from the a. Precambrian b. Paleozoic c. Mesozoic d. Cenozoic 38. A contact between parallel sedimentary rock that records missing geologic time is a. a disconformity b. an angular unconformity c. a nonconformity d. a sedimentary contact Expanding Your Knowledge 1. Why do some rocks fold while others are faulted? 2. In what parts of North America would you expect to find the most intensely folded rock? 3. A subduction zone can be regarded as a very large example of what type of fault? 4. Looking at the San Andreas fault, shown in box 6.2, figure 1, where might restraining bends form? What kind of structures might form there? 5. What features in sedimentary or volcanic rock layers would you look for to tell you that the rock was part of the overturned limb of a fold? 6. How much of the 238U originally part of Earth is still present? 7. As indicated by fossil records, why have some ancient organisms survived through very long periods of time whereas others have been very short-lived? 8. To what extent would a composite volcano (see chapter 10) be subject to the three principles described in this chapter? 9. 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? 10. Note that in table 8.2, the epochs are given only for the Cenozoic Era (as is commonly done in geology textbooks). Why are the epochs for the Mesozoic and Paleozoic considered less important and not given? 11. Why would you not be able to use the principle of superposition to determine the age of a sill (defined in chapter 11)? 12. Using information from box 8.4, calculate the age of a feldspar. At present, there are 1.2 million atoms of 40K. The amount of 40Ar in the mineral indicates that originally, there were 1.9 million 40K atoms in the rock. Use a half-life of 1.3 billion years. (Hint: The answer is 862 million years.) Chapter 3. Testing Your Knowledge Use the following questions to prepare for exams based on this chapter. 1. What factors control a stream’s velocity? 2. Describe how bar deposition creates a braided stream. 3. In what part of a large alluvial fan is the sediment the coarsest? Why? 4. What does a trellis drainage pattern tell about the rocks underneath it? 5. Describe one way that incised meanders form. 6. How does a meander neck cutoff form an oxbow lake? 7. How does a natural levee form? 8. Describe how stream terraces form. 9. Describe three ways in which a river erodes its channel. 10. Name and describe the three main ways in which a stream transports sediment. 11. How does a stream widen its valley? 12. What is base level? 13. The total area drained by a stream and its tributaries is called the a. hydrologic cycle b. tributary area c. divide d. drainage basin 14. Stream erosion and deposition are controlled primarily by a river’s a. velocity b. discharge c. gradient d. channel shape e. channel roughness 15. What is the gradient of a stream that drops 10 vertical feet over a 2-mile horizontal distance? a. 20 feet per mile b. 10 feet per mile c. 5 feet per mile d. 2 feet per mile 16. What are typical units of discharge? a. miles per hour b. cubic meters c. cubic feet per second d. meters per second 17. Hydraulic action, solution, and abrasion are all examples of stream a. erosion b. transportation c. deposition 18. 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 19. A river’s velocity is _____ on the outside of a meander curve compared to the inside. a. higher b. equal c. lower 20. Sandbars deposited on the inside of meander curves are called a. dunes b. point bars c. cutbanks d. none of the preceding 21. Which is not a drainage pattern? a. dendritic b. radial c. rectangular d. trellis e. none of the preceding 22. The broad strip of land built up by sedimentation on either side of a stream channel is a. a flood plain b. a delta c. an alluvial fan d. a meander 23. The average time between floods of a given size is a. the discharge b. the gradient c. the recurrence interval d. the magnitude 24. 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 25. What conditions are necessary for an artesian well? 26. What distinguishes a geyser from a hot spring? Why does a geyser erupt? 27. What is karst topography? How does it form? 28. What chemical conditions are necessary for caves to develop in limestone? For stalactites to develop in a cave? 29. What causes a perched water table? 30. Describe several ways in which ground water can become contaminated. 31. Discuss the difference between porosity and permeability. 32. What is the water table? Is it fixed in position? 33. Sketch four different origins for springs. 34. What controls the velocity of groundwater flow? 35. Name several geologic materials that make good aquifers. Define aquifer. 36. How does petrified wood form? 37. What happens to the water table near a pumped well? 38. How does a confined aquifer differ from an unconfined aquifer? 39. 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 40. 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 41. The subsurface zone in which all rock openings are filled with water is called the a. saturated zone b. water table c. unsaturated zone d. aquiclude 42. 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 ground water c. a body of rock that is impermeable 43. Which rock type would make the best aquifer? a. shale b. mudstone c. sandstone d. all of the preceding 44. Which of the following determines how quickly ground water flows? a. elevation b. water pressure c. permeability d. all of the preceding 45. Ground water 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 46. The drop in the water table around a pumped well is the a. drawdown b. hydraulic head c. porosity d. fluid potential Expanding Your Knowledge 1. Several rivers have been set aside as “wild rivers” on which dams cannot be built. Give at least four arguments against building dams on rivers. Give at least four arguments in favor of building dams. 2. Discuss the similarities between deltas and alluvial fans. Describe the differences between them. 3. How is the recurrence interval for a flood determined? How may new data affect the flood-frequency curve? 4. What affect would global warming have on the overall water budget in the hydrologic cycle? How might this influence the dynamics of a stream? 5. 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. 6. Where should high-level nuclear waste from power plants be stored? If your state or community uses nuclear power, where is your local waste stored? 7. Should all contaminated ground water be cleaned up? How much money has been set aside by the federal government for cleaning polluted ground water? Who should pay for groundwater cleanup if the company that polluted the water no longer exists? Should some aquifers be deliberately left contaminated if there is no current use of the water or if future use could be banned? 8. Why are most of North America’s hot springs and geysers in the western states and provinces? Chapter 4. Testing Your Knowledge Use the following questions to prepare for exams based on this chapter. 1. Why are some minerals stable several kilometers underground but unstable at Earth’s surface? 2. Describe what happens to each mineral within granite during the complete chemical weathering of granite in a humid climate. List the final products for each mineral. 3. Explain what happens chemically when calcite dissolves. Show the reaction in a chemical equation. 4. Why do stone buildings tend to weather more rapidly in cities than in rural areas? 5. Describe at least three processes that mechanically weather rock. 6. How can mechanical weathering speed up chemical weathering? 7. Name at least three natural sources of acid in solution. Which one is most important for chemical weathering? 8. What is the difference between a residual soil and a transported soil? 9. What factors affect the formation of soil? 10. How do soils erode, and why is it important to minimize soil erosion? 11. What are the soil horizons? How do they form? 12. Physical disintegration of rock into smaller pieces is called a. chemical weathering b. transportation c. deposition d. mechanical weathering 13. The decomposition of rock from exposure to water and atmospheric gases is called a. chemical weathering b. transportation c. deposition d. mechanical weathering 14. Which is not a type of mechanical weathering? a. frost wedging b. frost heaving c. pressure release d. oxidation 15. The single most effective agent of chemical weathering at Earth’s surface is a. carbonic acid H2CO3 b. water H2O c. carbon dioxide CO2 d. hydrochloric acid HCl 16. The most common end product of the chemical weathering of feldspar is a. clay minerals b. pyroxene c. amphibole d. calcite 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 18. Soil with approximately equal amounts of sand, silt, and clay along with a generous amount of organic matter is called a. loam b. inorganic c. humus d. caliche 19. Which is characteristic of soil horizons? a. they can be distinguished from one another by appearance and chemical composition b. boundaries between soil horizons are usually transitional rather than sharp c. they are classified by letters d. all of the preceding 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 21. Hardpan forms in the a. A horizon b. B horizon c. C horizon d. E horizon 22. What are two reasons why parts of the southwestern United States have an arid climate? 23. Sketch a cross section of an idealized dune, labeling the slip face and indicating the wind direction. Why does the dune move? 24. Describe the geologic structure and sketch the major landforms of a. the Colorado Plateau b. the Basin and Range province 25. How does a flash flood in a dry region differ from most floods in a humid region? 26. Give two reasons why wind is a more effective agent of erosion in a desert than in a humid region. 27. Name four types of sand dunes and describe the conditions under which each forms. 28. 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 29. Which is characteristic of deserts? a. internal drainage b. limited rainfall c. flash floods d. slow chemical weathering e. all of the preceding 30. The major difference between a mesa and a butte is one of a. shape b. elevation c. rock type d. size 31. The Basin and Range province covers almost all of a. Utah b. Nevada c. Texas d. Colorado 32. 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 33. Rocks with flat, wind-abraded surfaces are called a. ventifacts b. pediments c. bajadas d. none of the preceding 34. The removal of clay, silt, and sand particles from the land surface by wind is called a. deflation b. depletion c. deposition d. abrasion 35. Which is not a type of dune? a. barchan b. transverse c. parabolic d. longitudinal e. all of the preceding are dunes 36. Much of the southwestern United States is desert because (choose as many as apply) a. it is near 30° North b. the western mountains create a rain shadow c. cold ocean currents in the Pacific cause high evaporation rates in the land d. it is a great distance from the ocean 37. 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 38. A surface layer of closely packed pebbles is called a. desert varnish b. deflation c. a blowout d. desert pavement Expanding Your Knowledge 1. Which mineral weathers faster—hornblende or quartz? Why? 2. Compare and contrast the weathering rate and weathering products for Ca-rich plagioclase in the following localities: a. central Pennsylvania with 40 inches of rain per year; b. Death Valley with 2 inches of rain per year; c. an Alaskan mountaintop where water is frozen year-round. 3. The amount of carbon dioxide gas has been increasing in the atmosphere for the past 40 years as a result of the burning of fossil fuels. What effect will the increase in CO2 have on the rate of chemical weathering? The increase in CO2 may cause substantial global warming in the future. What effect would a warmer climate have on the rate of chemical weathering? Give the reasons for your answers. 4. In a humid climate, is a soil formed from granite the same as one formed from gabbro? Discuss the similarities and possible differences with particular regard to mineral content and soil color. 5. Study the photos of sand dunes in this chapter. Which way does the prevailing wind blow in each case? 6. Can deserts be converted into productive agricultural regions? How? Are there any environmental effects from such conversion? 7. At what relative depth is ground water likely to be found in a desert? Why? Is the water likely to be drinkable? Why? Chapter 5. Testing Your Knowledge Use the following questions to prepare for exams based on this chapter. 1. Describe in detail how earthquake epicenters are located by seismograph stations. 2. What causes earthquakes? 3. Compare and contrast the concepts of intensity and magnitude of earthquakes. 4. Name and describe the various types of seismic waves. 5. Discuss the distribution of earthquakes with regard to location and depth of focus. 6. Show with a sketch how the concept of plate tectonics can explain the distribution of earthquakes in a Benioff zone and on the crest of the mid-oceanic ridge. 7. Describe several techniques that may help scientists predict earthquakes. 8. How may the timing of earthquakes someday be controlled? 9. Describe several ways that earthquakes cause damage. 10. How do earthquakes cause tsunami? 11. What are aftershocks? 12. The elastic rebound theory a. explains folding of rocks b. explains the behavior of seismic waves c. involves the sudden release of progressively stored strain in rocks, causing movement along a fault d. none of the preceding 13. The point within Earth where seismic waves originate is called the a. focus b. epicenter c. fault scarp d. fold 14. P waves are a. compressional b. transverse c. tensional 15. 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 16. 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 17. Benioff zones are found near a. midocean ridges b. ancient mountain chains c. interiors of continents d. oceanic trenches 18. Most earthquakes at divergent plate boundaries are a. shallow focus b. intermediate focus c. deep focus d. all of the preceding 19. Most earthquakes at convergent plate boundaries are a. shallow focus b. intermediate focus c. deep focus d. all of the preceding 20. A zone of shallow earthquakes along normal faults is typical of a. divergent boundaries b. transform boundaries c. subduction zones d. collisional boundaries 21. 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 22. 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 Expanding Your Knowledge 1. What are some arguments in favor of and against predicting earthquakes? What would happen in your community if a prediction were made today that within a month, a large earthquake would occur nearby? 2. Most earthquakes occur at plate boundaries where plates interact with each other. How might earthquakes be caused in the interior of a rigid plate? 3. How can you prepare for an earthquake in your own home? 4. Suppose you want to check for earthquake danger before buying a new home. How can you check the regional geology for earthquake dangers? The actual building site? The home itself? Chapter 6-9 Testing Your Knowledge Use the following questions to prepare for exams based on this chapter. 1. Describe the effect on shear strength of the following: a. slope angle b. orientation of planes of weakness c. water in soil d. vegetation 2. Compare the shear force to the force of gravity (drawing diagrams similar to figure 13.2) for the following situations: a. a vertical cliff b. a flat horizontal plane c. a 45° slope 3. How does a rotational slide differ from a translational slide? 4. What role does water play in each of the types of mass wasting? 5. Why is solifluction more common in colder climates than in temperate climates? 6. List and explain the key factors that control mass wasting. 7. What is the slowest type of mass wasting process? a. debris flow b. rockslide c. creep d. rockfall e. avalanche 8. The largest landslide has taken place a. on the sea floor b. in the Andes c. on active volcanoes d. in the Himalaya 9. A descending mass moving downslope as a viscous fluid is referred to as a a. fall b. landslide c. flow d. slide 10. 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 11. The resistance to movement or deformation of soil is its a. mass b. shear strength c. shear force d. density 12. Flow of water-saturated soil over impermeable material is called a. solifluction b. flow c. slide d. fall 13. A flowing mixture of soil and water, usually moving down a channel is called a a. mudflow b. slide c. fall d. earthflow 14. An apron of fallen rock fragments that accumulates at the base of a cliff is called a. bedrock b. sediment c. soil d. talus 15. How does construction destabilize a slope? a. adds weight to the top of the slope b. decreases water content of the slope c. adds weight to the bottom of the slope d. increases the shear strength of the slope 16. How can landslides be prevented during construction? (choose all that apply) a. retaining walls b. cut steeper slopes c. install water drainage systems d. add vegetation Expanding Your Knowledge 1. Why do people fear earthquakes, hurricanes, and tornadoes more than they fear landslides? 2. If you were building a house on a cliff, what would you look for to ensure that your house would not be destroyed through mass wasting? 3. 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? 4. Can any of the indicators of creep be explained by processes other than mass wasting?