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GLY 2010 - Section 51060 August 6, 2012 105 points 35 students took exam Name Z# Evolution of the Earth -- Final Examination Key THIS IS A CLOSED BOOK, CLOSED NOTE EXAMINATION. ANY USE OF BOOKS, NOTES, ETC. IS CHEATING. ALL ELECTRONIC DEVICES (CELL PHONES, COMPUTERS, ETC.) MUST BE TURNED OFF AND OUT OF SIGHT. USE OF ELECTRONIC DEVICES IS CHEATING. ANY FORM OF CHEATING WILL RESULT IN AN F IN THE COURSE AND REFERRAL TO THE STUDENT CONDUCT COMMITTEE FOR FURTHER DISCIPLINARY ACTION. You have until 12:55 p.m. for this examination. If you finish early, check your exam. Be sure you answered all questions. Numbers in red to the left of the question number are the number of incorrect responses. Blue text is instructor comments, not on the original test. True-False -Print the letter T or F in the blank to indicate if each of the following statements is true or false. Illegible answers are wrong. (1 point each) 1. Deep focus earthquakes are associated only with convergent plate margins. 15 T 4 T 2. The widest continental shelves are associated with passive plate margins. The east coast of Florida is an example. 4 F 3. The initial rupture point of an earthquake, where strain energy is first converted to elastic wave energy, is known as the epicenter. 10 T 4. A mid-ocean ridge is more apt to have a rift valley if it spreads slowly, rather than rapidly. 10 T 5. Lithospheric plates are thinnest in the oceans. 2 F 6. An instrument that detects, magnifies, and records vibrations is a hydrograph. 6 F 7. Hydrothermal vents known as black smokers emit clouds of sulfide minerals and are colder than white smokers, which emit no sulfides. 9 T 8. The great basalt plateaus of the continents (Columbian, Deccan) mark current or ancient rift zones 6 T 9. Low frequency sound waves used in seismic profiling can cause problems for forms of marine life, such as dolphins, that use sound waves for echolocation. 1 21 F 10. Continental shelf materials are mostly of marine origin. As discussed in class, the shelves are extensions of the continents, and will be uncovered during glacial periods. They are composed mostly of detritus off the continents. 12 T 11. The deep ocean basins cover about 30% of the earth’s surface, similar to that covered by land. 26 F 12. The mid-ocean ridges are mountains found on the floor of the Pacific, Indian, and Atlantic Oceans. 4 F 13, In the entire four billion year history of the earth, there has only been one supercontinent, known as Pangaea. 6 T 14. Wildfires increase the possibility of mass movements, especially the very destructive debris flows. 6 T 15. A blast of air, approaching hurricane force, may precede the front of a large mass movement 17 F 16. The collective name for all stream deposited sediment is colluvium. Alluvium, not colluvium. 6 T 17. Lahars are a special type of mudflow produced on the slopes of a volcano. Volcanic ash and hot gases melt accumulated snow and glacial ice, producing large quantities of mud. 7 F 18. The velocity of a stream is nearly constant across the entire width of the stream, so measuring stream velocity at one point is sufficient to insure good quality data. 1 T 19. Construction of a dam across a river temporarily establishes a new base level for the river, until the dam is removed or collapses. This may slow the river velocity above the dam, causing sediment to be deposited. 3 T 20. The largest size particle diameter a stream can carry is proportionate to the square of the streams velocity, which is why floods sometimes move huge boulders. 11 F 21. When the river gradient is steep, the cross-sectional profile of a river cut stream channel will be U-shaped. 20 F 22. The ability of a rock or sediment to allow a fluid (water) to flow through it is known as the porosity. 0 T 23. Unconfined aquifers, such as the Biscayne Aquifer in South Florida, are subject to rapid recharge from above, but may also be easily contaminated by spills, especially if they are shallow. 2 0 T 24. Artificial clay layers are used to line landfills, so that water from the landfill won’t leach into the aquifer, because the clay layer acts as an aquiclude. 17 F 25. In order to get water from an artesian well, it is necessary to pump the water to the surface. By definition, artesian wells are self-pressurized. 9 F 26. The use of geothermal fluids to generate power is pollution-free, since the fluids are extremely pure fresh water. 0 T 27. In improperly constructed drinking water wells, sewage effluent from septic tanks can infiltrate the drinking water supply. 5 T 28. Worldwide, more than 85% of glaciers are retreating. 10 T 29. Valley glaciers are confined by surrounding bedrock highlands, and generally move down steep to very steep surfaces. 17 F 30. Glaciers can form on land or in the ocean. 6 T 31. Loess, derived from Pleistocene glaciers, is found as far south as Louisiana and Mississippi. 19 F 32. Periodic variations of the earth’s orbit and axial rotation can explain all of the observed changes in global climate within the time frame these changes have been observed, from the beginnings of the industrial revolution to the present. Orbital variations have periods from tens to 100's of thousands of years, and have very little effect over a less than 200 year period. 9 T 33. Milder winters in high latitudes lead to climate warming, and greater snowfall. Cooler summers would reduce snowmelt. Combined, this might trigger ice formation, and lead to an ice age. 2 T 34. Certain gases, known as greenhouse gases, absorb infrared radiation, and prevent it from escaping from earth. This raises the average global temperature. 9 T 35. After a rapid increase in sea-level from 16,0000 to 8,000 years before present, sealevel has been nearly constant for 8000 years. Since 1900, it has risen about 20 centimeters, and the rate of rise is accelerating. 13 F 36. A desert is a hot, arid region. 4 T 37. In hyper-arid regions, such as the Sahara and Atacama deserts, the potential annual evaporation divided by recorded average annual precipitation may exceed 100. 3 5 F 38. “Desert pavement” refers to a surface coating sprayed by humans on the surface of arid regions to prevent aeolian erosion. 28 F 39. In the dust bowl movie shown in class, and the picture of the storm approaching a village in Senegal, the material in the air was composed mainly of sand, accounting for the name “sandstorm”. This is dust, not sand, which is too heavy to rise high. 11 F 40. Alluvial fans and sand dune deposits both obey the Law of Original Horizontality. 10 T 41. After glaciers melt, the land under them rises. This is still occurring in the area north of Lake Superior. 24 F 42. On both the east and west coasts of the United States, longshore currents carry sand from south to north. North to south 7 T 43. Erosion of a headland can create a sea-arch, which can be further eroded to form a sea stack. 6 T 43. Hooks, such as the northern tip of Cape Cod, caused be refraction of waves around the spit. 16 T 44. Waves and ocean currents transport energy, whose source is either solar radiation or gravitation interaction. 15 F 45. Competence is the maximum load a stream can carry, which is directly related to the discharge of a stream. 3 F 46. Human teeth are composed of calcium phosphate, and have a structure like the mineral apatite. Teeth are therefore examples of minerals. Midterm repeat 15 F 47. In the rock cycle, sedimentary rocks may be converted to metamorphic rocks, but it is not possible to convert metamorphic rocks to igneous rocks. Midterm repeat 5 T 48. Large volcanic eruptions, like Mount Pinatubo in 1991, can cool the earth’s climate for one to several years. Midterm repeat 8 T 49. Graded-beds are formed when heavy or large particles sink from a turbidity current first, followed by medium, then small, particles. Midterm repeat 9 F 50. The top of Mt. Everest is composed of marine limestone, indicating that the earth was flooded to a depth at least 30,000 feet higher than today’s sea-level. Midterm repeat 4 T 51. Metamorphic fluids often produce ion exchange, which can partially or totally reset radiometric clocks. Midterm repeat 4 Multiple-Choice - Choose the best response to each statement or question. Print the letter corresponding to your choice in the blank. (1 point each) 1 A 1. What are the most intense energy release per unit time of any natural event, except for meteorite impacts? A. Earthquake B. Hurricane C. Tornado D. Tsunami 24 C 2. The East African rift zone is an example of what type of plate boundary? A. Convergent ocean-ocean B. Divergent ocean-ocean C. Divergent continent-continent D. Transform ocean-continent 10 C 3. The San Andreas fault in California has which of the following features associated with it? A. Alkaline volcanism B. Fissure type volcanic eruptions C. Shallow focus earthquakes D. None of the above 13 C 4. L. Wilson Morley and, nine months later, Frederick Vine and Drummond H. Matthews proposed an explanation of magnetic stripes. What idea, not widely accepted in 1963, did their explanations depend on? A. Sea-floor spreading, as proposed by Harry Hess and Robert Dietz B. Polarity reversals of the earth’s magnetic poles C. Both of the above D. None of the above 14 D 5. Shallow, intermediate, and deep focus earthquakes are associated with which type of plate boundary? A. Convergent ocean-continent B. Convergent ocean-ocean C. Divergent ocean-continent D. Both A and B 5 6 C 6. Who first proposed a scientifically correct explanation of magnetic stripes, although his paper was initially rejected and he often does not get credit for his idea? A. H. Bretz B. D. Mathews C. L. Morley D. F. Vine 8 D 7. Most active continental margins are found where? A. In the Atlantic ocean B. In the Arctic ocean C. In the Indian ocean D. In the Pacific ocean 11 C 8. These features makes up only 7.5% of the ocean surface, yet contains much of the wealth of the ocean, including petroleum, natural gas, mineral resources, and huge sand and gravel deposits. A. Abyssal plains B. Continental rises C. Continental shelves D. Oceanic plateaus 1 C 9. Oceans cover about what percentage of the earth’s total surface? A. 40 B. 55 C. 70 D. 85 20 D 10. On which of the following regions of the ocean floor is the slope angle the highest? A. Abyssal plain B. Continental rise C. Continental shelf D. Continental slope 22 C 11. These features are created by mantle plume volcanism producing copious lavas which cover and smooth large areas of the ocean floor. The rock consists primarily of pillow lava, which may reach or exceed 30 kilometers in thickness. They resemble the flood basalt provinces found on the continents. Which feature is this? A. Abyssal plain B. Deep sea fan C. Ocean plateau D. Seamount 6 6 D 12. Which of the following descriptions fits that of the mid-ocean ridges? A. They exceed 70,000 kilometers in length B. They range from 1000 to 4000 kilometers in width C. They cover 20% of the earth’s surface D. All of the above 3 D 13. Mass movement is influenced by which of the following factors? A. Slope Steepness B. Vegetation C. Water D. All of the above 17 D 14. Which of the following is an example of slow mass movement? A. Debris avalanche B. Earthflow C. Slump D. Solifluction 4 B 15. The smallest division of a drainage network is called a: A. Primary B. Rill C. Secondary D. Trunk 1 D 16. Streams may: A. Erode their stream beds, making the stream channel deeper B. Flow over the stream bed with little deposition or erosion C. Actively deposit sediment on the stream bed, building it up D. Either A, B, or C, depending on the conditions at a particular time 8 A 17. The most common type of river drainage pattern is: A. Dendritic B. Radial C. Straight D. Trellis 11 C 18. Approximately two-thirds of the groundwater use in the United States is for: A. Aquaculture B. Drinking water C. Irrigation D. Livestock 7 6 A 19. Deep inside a glacial crevasse, or inside an ice tunnel under a glacier, what color light will be seen? A. Blue B. Green C. Red D. White 24 C 20. Which of the following features is not due to glacial erosion? A. Arte B. Cirque C. Lateral moraine are depositional D. Roche moutonnée 27 C 21. Which of the following can create a dam, similar to an earth-fill dam created by a human engineer? A. Lateral moraine B. Medial moraine C. Terminal moraine D. All of the above 18 B 22. When two or more valley glaciers merge, what type of moraine will form as the result of the merger? A. Lateral moraine B. Medial moraine C. Terminal moraine D. All of the above 21 A 23. Who first proposed, in 1837, that earth had experienced an ice age? A. Louis Agassiz B. J. Harlan Bretz C. Charles Darwin D. Milutin Milankovitch 19 A 24. During the Pleistocene epoch of the Cenozoic era, how many times did ice move south out of Canada into the United States? A. At least four B. Three C. Two D. One 8 9 D 25. Who first formulated an idea that explained the cause of the Pleistocene glacialinterglacial oscillation by a series of periodic variations of the earth’s orbit and axial rotation? A. Louis Agassiz B. J. Harlan Bretz C. Charles Darwin D. Milutin Milankovitch 4 D 26. Deserts may result from: A. Air-circulation patterns, such as the downdraft regions of Hadley cells B. Rain shadow effects, where air passing over mountain ranges loses moisture before descending as a dry air mass C. Proximity to a region of cold ocean water, where little evaporation occurs D. Any of the above 30 B 27. Which of the following is NOT an erosional landform found in arid regions? A. Alluvial fan B. Barchan dune are depositional C. Inselberg D. Mesa 18 D 28. Which of the following dune types are found along A1A and other coastal regions in Florida where the predominant winds are on or off-shore? A. Barchan B. Seif C. Star D. Transverse 14 A 29. In some parts of Florida, the coast is lined by mangroves. This is an example of what type of coast? A. Organic B. Primary C. Secondary D. Could be any of the above 28 B 30. The presence of a wave-cut bench breaks the force of the waves, and may result in the formation of what? A. Cove B. Headland C. Sea-arch D. Sea-stack 9 11 B 31. Which era is known as the age or reptiles, including dinosaurs? Midterm repeat A. Cenozoic B. Mesozoic C. Paleozoic D. None of the above 10 A 32. Which part of the earth, because if is warm and under pressure, behaves as a plastic, capable of slow deformation? This part is important because it allows the earth’s plates to move without severe deformation. Midterm repeat A. Asthenosphere B. Core C. Lithosphere D. Mesosphere 11 C 33. Which type of chemical bonding has allowed salts to be transferred from the lands surface to the ocean, by ths process of dissolution? Midterm repeat A. Covalent B. Hydrogen C. Ionic D. Metallic 7 D 34. Rocks are: Midterm repeat A. An aggregate of one or more minerals B. A body of undifferentiated mineral or glassy matter C. Bodies of solid organic matter D. Any of the above 12 C 35. Which of the following layers of the earth is a liquid? Midterm repeat A. Crust B. Mantle C. Outer core D. Inner core 12 C 36. Which chemical weathering process is responsible for the conversion of feldspars, the most common minerals in the earth’s crust, to clay, an important part of soil? Midterm repeat A. Dissolution B. Hydration C. Hydrolysis D. Oxidation 10 15 A 37. Which soil horizon is a mixture of inorganic mineral matter and humus, dark colored decomposed organic matter? Midterm repeat A. A-horizon B. B-horizon C. C-horizon D. O-horizon 16 B 38. Most sedimentary rocks originate from which source? Midterm repeat A. From chemical precipitation of solids from aqueous solutions B. From fragments of preexisting rocks C. From precipitates created by living organisms, such as shells D. All are about the same 13 A 39. Geologists know that a fault is younger than the beds it offsets because of which of the following laws or principles? Midterm repeat A. Principle of Cross-cutting Relation-ships B. Principle of Inclusions C. Law of Original Horizontality D. Law of Superposition Fill-Ins - Write or print in the word or words which best completes each statement or answers each question. When the statement says “name and describe”, names without descriptions will receive no credit. Diagrams may be used to supplement answers, where useful. Illegible answers are WRONG. (1 point per blank) 6 1. The MERCALLI scale of earthquake intensity ranges from I to XII, and is based on human perception of the earthquake, and damage observed after the earthquake is over. 22 2. A WATERSHED (drainage basin) is the total area from which water reaches a stream 25 3. The WATER TABLE 26 4. The ratio of isotopic abundance among isotopes of which element are used as a separates the vadose zone from the phreatic zone. geothermometer, allowing us to closely estimate the temperature at various times in the earth’s past? 33 OXYGEN 5. The movement of sand grains up a dune face by bouncing along the surface is known as SALTATION 17 . 6. DESERTIFICATION means degradation of land and vegetation, soil erosion and the loss of top soil and fertile land in arid, semi-arid, and dry sub-humid areas, caused primarily by human activities and climate variation 11 6 7. How can a swimmer escape from a rip current? PERSONS CAUGHT IN A RIP CURRENT SHOULD SWIM SIDEWAYS TO GET OUT OF THE NARROW FLOW, THEN TURN AND SWIM BACK TO SHORE. 22 8. Viscosity increases as the silica content of magma increases. Why? AS SILICATE CONTENT INCREASES, MORE CHAINS OF SILICATE TETRAHEDRON FORM. THESE CHAINS WRAP AROUND EACH OTHER, INCREASING THE INTERNAL RESISTANCE TO FLOW, WHICH IS THE DEFINITION OF VISCOSITY. 20.5 9. What is the definition of mass movement? MASS MOVEMENT INVOLVES THE TRANSPORTING OF EARTH MATERIALS DOWNSLOPE, DUE TO GRAVITY, WITHOUT THE AID OF A TRANSPORTING MEDIUM, SUCH AS WATER OR ICE . 10-12. For a divergent ocean-ocean plate boundary, indicate the depth(s) of the associated earthquake foci, the type of volcanism (if any), and give a real example of this type of plate boundary 25 10. Earthquake depth? SHALLOW FOCUS 25 11. Type of volcanism? FISSURE ERUPTION 19 12. Real example? ANY MID-OCEAN RIDGE 13-14 Describe two unique physical features of earth, not known to exist on any other planet in our solar system. Be specific. Midterm repeat 14.5 13. LIQUID WATER ON THE SURFACE - SOME OTHER PLANETS HAVE WATER, BUT IT IS EITHER PRESENT AS VAPOR, OR WATER ICE. 11 14. FREE OXYGEN IN THE ATMOSPHERE - FREE OXYGEN MEANS THE OXYGEN IS NOT COMBINED WITH ANY OTHER ELEMENT. IT IS THE PRODUCT OF PHOTOSYNTHESIS. OTHER PLANETS HAVE OXYGEN, BUT ALWAYS COMBINED WITH OTHER ELEMENTS. 12 Matching - Match the description or answer the question in column one with the term associated with it from column two by printing the correct letter in each blank. Answers may be used once, more than one, or not at all (One point each) Column 2 Column 1 4 5 8 C 1. An imperceptibly slow down-slope movement of soil and near-surface rock materials, best discerned through the movement or response of objects affected by the process. A. Arte E 2. The vertical drop in elevation over a given horizontal distance, which may be expressed in units like meters/kilometer, feet/mile, or as a percentage, is known as what? D. Flow G 3. This process is a physical process that takes place during some earthquakes that may lead to ground failure; as a consequence, soft, young, water-saturated, well sorted, fine grain sands and silts behave as viscous fluids rather than solids G. Liquefaction B. Cone of depression C. Creep E. Gradient F. Horn H. Ophiolite I. Phreatic J. Playa 21 I 4. In the zone of saturation, all available pore spaces are filled with water. What is wanother term for this zone? K. Slide L. Solifluction 6 6 26 H 5. This type of rocks comprise the oceanic crust. They are mafic, but often include serpentinite, formed by metasomatitism of the mafic rock M. Tarn N. Tephra O. Vadose K 6. A form of mass movement in which a single intact mass (rock, soil, or unconsolidated material) moves downslope along a slip plane. P. Well drawdown B 7. Rapid withdrawal of fluid from a well causes a localized lowering of the water table around the well Key word is localized, which precludes “P” 13 19 A. Arte M 8. This type of lake forms in a cirque created by glacial erosion. B. Cone of depression 10 13 4 A 9. Knife-edged ridge of land, formed by parallel erosion of two alpine glaciers C. Creep F 10. A three or four-sided mountain, cut by glaciers flowing off an isolated mountain in several directions D. Flow N 11. A general term for fragments of volcanic rock and lava that, regardless of size, are blasted into the air by explosions or carried upward by hot gases in eruption columns or lava fountains F. Horn E. Gradient G. Liquefaction H. Ophiolite I. Phreatic J. Playa K. Slide L. Solifluction M. Tarn N. Tephra O. Vadose P. Well drawdown HAVE A GREAT SUMMER! 14 Final Examination Grades (105 possible) 99.5 97.0 91.0 88.5 87.0 85.0 - 2 83.5 83.0 - 2 81.0 80.5 - 2 80.0 78.5 78.0 77.0 75.5 75.0 73.5 73.0 72.5 - 2 71.5 70.5 70.0 69.0 - 2 67.0 - 2 65.0 62.0 60.5 52.5 47.5 A AB B- C+ C MEAN = 75.8 (72.1%) MEDIAN = 75.5 C- D+ D D- F In 2011, the mean was 75.6, and the median was 74.5 Comment: There were 18 “Midterm repeat” questions, and the scores on many were not good. Missing a question once is understandable, but missing it twice shows a definite lack of preparation. 15