Geology 141(B): Fall, 2007Lecture Final Examination... Page 1 ...
Geology 141(B)Name .
Fall, 20079:00 a.m.13 December, 2007
GE141(B):
Earth and Environment
Final Examination
INSTRUCTIONS: PLEASE read these instructions and questions CAREFULLY and completely. If you do not understand a question as it appears on the exam, PLEASE ASK FOR CLARIFICATION!! It is to YOUR benefit to do so. This examination is worth 300 points, or 30% of your overall semester grade. Exams will be graded as quickly as possible; your individual point total will be entered on the last page to ensure that only you know how well you did on the exam, unless you choose to divulge that information to others.
Please remember that I CANNOT give any credit for responses I can't read! The number of points for each question is indicated in parentheses after the question.
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"We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology.... This is a prescription for disaster. We might get away with it for a while, but sooner or later this combustible mixture of ignorance and power is going to blow up in our faces."
- Carl Sagan
Section I: Multiple choice. Please circle the letter of the response that is correct or that BEST answers the question or completes the statement. Please read each question and possible response carefully. There is ONLY ONE BEST ANSWER for each question. Each question is worth 5 points; this section is therefore worth 200 out of the total of 300 for the exam. PLEASE READ EACH QUESTION AND RESPONSE OPTION CAREFULLY! I am not trying to trick you, but missing a key word in a question can result in an error in judgment!
1. The most abundant element, by weight, in the Earth's crust is
a. siliconc. oxygene. magnesium
b. irond. aluminumf. sulfur
2. Iceland as a volcanic island is particularly large because
a. it occurs above a particularly active subduction zone in the mid-Atlantic.
b. it both overlies a mantle plume ("hot spot") AND is part of the mid-oceanic
rise and ridge system (MORRS).
c. it is a remnant of continental crust from the earliest formation of the Earth.
d. it is formed from plate convergence between the North American and
Eurasian plates.
e. it is actually part of the North American Shield separated as the Atlantic
Ocean formed.
3. The rocks of coastal Maine are part of what is called Avalonia by geologists, and are separated from the geology of the rest of the state by the Norumbega Fault; Avalonia is a classic example of a(n)
a. accreted terranec. pillow lava belte. rift valley
b. Benioff zoned. subduction zonef. hot spot
4. The mid-oceanic rise and ridge system (MORRS) is, in plate tectonic terms,
a. a convergent zone of two oceanic plates, where they're both buckling
upwards to produce the ridges.
b. a convergent zone between two oceanic plates, where one is subducting
beneath the other
c. an uplifted zone along a giant transform fault, that extends the full length
of the MORRS throughout the world's oceans.
d. a divergent plate boundary, where new sea floor is being created by mantle
upwelling.
5. Nitrogen and sulfur are two elements that plants need to obtain from soils in relatively large quantities. These are critically important to the plants for
a. disease resistancec. structural strength
b. protein synthesisd. flowering
6. A biogenic sedimentary rock created from the cementation of fragments of seashells, foraminifera, and/or coral would be a(n)
a. arkosec. cherte. limestone
b. coald. dolomitef. shale
7. Minerals that are found only, or almost only, in metamorphic rocks will include all of the following except
a. kyanitec. actinolitee. garnet
b. staurolited. quartzf. chlorite
8. The metamorphic rock that would be created by applying heat and pressure to the rock that was the correct answer in #6, above, would be a
a. gneissc. granitee. marble
b. quartzited. schistf. phyllite
9. A graywacke is deposited in an offshore trench by rapid sedimentation on an actively subducting convergent plate margin. Over time, subduction pushes it deeper and deeper into the crust beneath the coastal mountains. Temperatures rise, and eventually it melts. When this hardens and recrystallizes, what rock is going to be the most likely end product?
a. gneiss b. quartzite c. schist d. granite e. marble f. phyllite
10. You've been touring eastern Turkey with a bunch of friends in search of the unusual in world destinations. In an isolated valley, you see an isolated mountain peak, which upon closer inspection is revealed to be what you expected to find: a volcano. WHAT KIND of volcano is this most likely to be, based on its topographic profile, and what kind of rock would you have most likely found on its flanks?
a. this is a shield volcano and I would have found a rhyolite.
b. this is a stratovolcano and I would have found a basalt.
c. this is a cinder cone and I would have found obsidian and pumice.
d. this is a stratovolcano and I would have found an andesite.
e. this is a shield volcano and I would have found a basalt.
11. The greatest potential hazard to local populations from a volcano such as the one above would be
a. pyroclastic flows of hot volcanic debris
b. rapid flows of hot, basaltic lavas.
c. hot springs erupting in people's basements.
d. development of hydrothermal vents ("black smokers") in the summit
caldera.
12. As igneous rock units, dikes are
a. any plutonic rock unit that is <100 km2 in aerial extent.
b. naturally occurring volcanic ridges in the Netherlands.
c. parallel-sided intrusions that cut across pre-existing rocks and structures.
d. flat-lying slabs of mafic volcanic rocks deposited as flood basalts.
13. An earthquake of magnitude 3 is strong enough to rattle dishes and be felt in a local area. One of magnitude 6 represents about how much more ground shaking than one of magnitude 3?
a. 2 times as muchc. 100 times as much e. 30 times as much
b. 10 times as muchd. 1000 times as much f. 27,000 times as much
14. "Greenstone belts" in the continental shields are often important mining areas, but in the history of the Earth represent remnants of ancient
a. island arc systems.c. oceanic crust (ophiolites).
b. segments of the MORRS.d. continental blocks.
15. The first seismic waves from an earthquake that will reach a seismograph
a. are the P-wavesc. are the surface waves
b. are the S-wavesd. varies with the rock types
16. The difference between the Mercalli Intensity Scale and the Richter Magnitude Scale for earthquakes is that
a. the Richter scale is subjective, based on damage that can be observed,
whereas the Mercalli scale is based on measurements of ground shaking.
b. the Mercalli scale is subjective, based on damage that can be observed,
whereas the Richter scale is based on measurements of ground shaking.
c. the Mercalli scale is used in Europe; the Richter scale is used in the
United States.
d. these are the old and new names for the same thing.
17. Surface creep, such as that which toppled the retaining wall along Silver Street (which you saw in class) is the result of
a. shaking by vibrations in the Earth, either by earthquakes or (in this case)
the heavy traffic on Silver Street.
b. repeated expansion and contraction of the slope, either by wet-dry cycles or
repeated freezing and thawing.
c. erosion of the base of slopes by streams, waves or human activities.
d. slow tectonic movement along minor faults.
18. Mass wasting is greatly helped by, and almost always involves
a. steep slopesc. deep weathering
b. abundant waterd. all of the above
19. Most sediments that are carried by streams get into the stream by
a. downcutting by the stream in its bed.
b. people dumping debris into the stream.
c. mass wasting of the banks and adjacent hillslopes.
d. volcanic eruptions.
e. erosion of point bar deposits.
20. Perennial streams keep flowing all year, even when it hasn't rained locally, because
a. it undoubtedly has rained elsewhere in their drainage basin.
b. snow is melting somewhere in the drainage basin.
c. organic decay of leaves and other materials yields water into the system.
d. groundwater flow along their courses slowly adds water to them.
21. The source of virtually all underground waters is
a. chemical weathering of minerals in the rocks.
b. infiltration of rainwater and melting snows.
c. water deposited with sediments in ancient streams and oceans.
d. underground rivers that originate in subduction zones.
e. magmas with origins in the upper mantle, like at Yellowstone.
22.
The sketch-map above shows the essential elements of the Whattamattawithya River floodplain in southwestern Alabama. At what locations is deposition of bed load materials going to be the dominant process taking place?
ABCDE
23. On the diagram above, at what location(s) would you expect deposition of silts and clays to be the dominant geological process taking place over time?
a. Ab. Bc. C and Dd. A and Ee. B and E
24. We used a couple simple chemical formulas to describe what occurs to form karst landscapes: CO2 + H2O H2CO3 H+ + (HCO3)-
H+ + CaCO3 Ca++ + (HCO3)-
What this all means is that
a. carbon dioxide gas dissolving in water makes the water dissolve limestone.
b. carbon dioxide gas dissolving in water will create new limestone.
c. we can counteract global warming if it rains more.
d. calcite dissolving in water will release carbon dioxide gas.
25. Significant sources of groundwater contamination could be derived from
a. improper burial of solid wastesd. poorly designed septic systems
b. pesticide and fertilizer residuese. saltwater intrusion in coastal areas
c. salts used to de-ice highwaysf. all of the above
26. Approximately what percentage of the people in your class rely in whole or part on groundwater resources for their home supply of water?
a. 27%b. 36%c. 45%d. 54%e. 63%f. 72%
27. The Great Plains (= Ogallala) Aquifer is in part a confined aquifer, which means that
a. its recharge area is far away, in this case, in the Rocky Mountains to the west.
b. the water in it is recharged from sources deep in the crust.
c. the water in it was present as the sediments making it up were deposited.
d. the water in it is available over a limited area, but in unlimited quantities.
28. The Ogallala Aquifer is suffering from aquifer drawdown, which means that its water is
a. being drawn out from underneath, into the crust and underlying mantle.
b. drying up, evaporating, underground in caves.
c. flowing out into deep underground rivers.
d. being withdrawn by human use faster than it's being recharged.
e. being removed by the natural vegetation more during the day than at night.
29. Glaciers modify the landscape by
a. holding vast amounts of water in solid form on land, forcing sea level to drop.
b. eroding vast amounts of rock and sediments from the landscape.
c. depositing vast amounts of rock and sediments on the landscape.
d. altering the distribution of plants and animals on the solid landscape.
e. all of the above.
f. none of the above
30. The dominant rock type in karst (solution-dominated) landscapes like Florida and Puerto Rico is
a. granited. basalt
b. schiste. gneiss
c. limestonef. sandstone
31. The dominant agent of erosion in deserts, in terms of the total volume of materials moved over time, is
a. running waterc. wind
b. mechanical weatheringd. mass wasting
32. Which of the following geologic units would you expect to be potentially the best aquifer type, demonstrating both high porosity and high permeability?
a. thickly bedded pumicec. well-sorted stream gravels
b. shaled. granite with only minor jointing
33. The Arecibo radiotelescope, used in the SETI (Search for ExtraTerrestrial Intelligence) program is located in
a. northwestern Pennsylvania, over a large glacial kettle.
b. Puerto Rico, over a large doline (karst depression).
c. the Yucatán Peninsula, over a meteor impact crater.
d. Mexico, over a large extinct volcanic caldera.
34. Ria coastlines, like those of Chesapeake Bay and Delaware Bay, owe their origin to
a. glacial scour of river valleys below modern sea level.
b. longshore drift removing vast amounts of sediments.
c. rivers downcutting below modern sea level during glaciations.
d. on-land extensions of transform faults on the Mid-Atlantic Ridge.
35. Coral Atolls, such as those of the Tuamotu Archipelago in the SW Pacific, come into existence by
a. mantle plumes generating large, high volcanic islands, as in the Galápagos
and Hawai'i.
b. longshore drift accumulating oolitic sands on top of ophiolite remnants.
c. gradual subsidence of volcanic islands, as tropical corals grow upwards.
d. artificial reef construction by multinational corporations specializing in
tourism.
36. The tides in the oceans (and large lakes, for that matter) are created by
a. flow within the liquid outer core of the Earth.
b. plate tectonic movements of the continents away from each other.
c. the frictional drag of wind on the surface of the oceans.
d. the gravitational pull of the sun and moon on the waters of Earth.
37. The United States imports over 25% of what we need of how many basic mineral resources?
a. only one - oild. ten to twelve
b. three: oil, gold, diamondse. over twenty
c. five or six
38. Many of the major mining districts of the world are located on modern or ancient tectonic plate margins. This is because
a. these are areas where fractures in the Earth's crust reveal the minerals
there.
b. many major ore-forming processes are igneous in nature.
c. these are the only areas people have looked, because they're in the mountains
and easily accessible.
d. these are areas where few people live, so environmental regulation isn't as
difficult as it would be in other areas.
39. Which of the following would be an excellent trap for potential oil extraction?
a. a granitic stockd. an anticline or dome in sedimentary rocks
b. a mafic dike in granitee. a syncline in sedimentary rocks
c. a transform fault on the MORRS
40. Approximately how much earth material is extracted in the U.S.A. each year for every man, woman and child in the country? (I.e., what is the mean per capita consumption of mineral resources in the U.S.A.?)
a. about 100 pounds (50 kg)c. about 1000 pounds (500 kg)
b. about 500 pounds (250 kg)d. over 20 tons (10,000 kg)
Section II: Short answers, fill-ins, etc. Please respond to each question in the most appropriate fashion; make your responses concise and to the point, but thorough. There should be ample space provided for an adequate response. PLEASE WRITE LEGIBLY; I can't give credit for responses I can't read! Please make all verbal responses in complete sentences and proper English and avoid using cryptic abbreviations or shorthand notation such as b/c, w/, etc. The number of points for each question is indicated in parentheses after the question; there are 100 points possible for the entire section. (And PLEASE remember that, as promised on the syllabus, I will deduct a point each time I see "volcanoe" or "techtonic!" )
IMPORTANT! Please note that the space left behind a question should be sufficient to properly respond thoroughly. An 8-centimeter space should be taken as a major hint that you need more than two or three words to respond adequately to a given question.
51. The fact that the same fossil organisms (both plants and animals) have been found in North America and Europe, or in South America, Africa, India, Australia and Antarctica, is often cited as one line of evidence for the validity of plate tectonic theory. WHY is this unusual, and how does it provide evidence in support of continental drift? (10 points)
52. There are five major factors that dictate the ultimate character of a soil, formed as a result of the chemical weathering of rocks and sediments. What are these factors? (5 points: 1 point each).
53. Below is a labeled cartoon sketch of a section you've discovered in a cliff face in southwestern Utah. Note that there are some SERIOUS dinosaur bones in this
section. You know, from your ancient geology class at Colby, that dinosaurs died out back around 65 million years ago, when that giant comet or asteroid smashed into the Yucatán Peninsula. But you don't know about these particular dinosaur bones, which may well be an undescribed new species. HOW would you go about determining how old these bones are? (I.e., what rock units would you use for radiometric age determinations, and what technique(s) would you utilize, in order to get a numerical age estimate for these specimens?)(10 points)
54. Metamorphic rocks are, in composition and character, the most varied of all rocks on the face of the Earth. What are the four factors that can vary completely independently to produce this diversity? (5 points: 2-1-1-1)
55. What do scientists believe is the ultimate origin of the volcanic activity, hot springs, etc., that dominate Yellowstone National Park in northwestern Wyoming? (5 points)
56. Complete the table below with the name of each of the sediment types indicated by the grain size at left, and the common clastic sedimentary rock types derived from each. (10 points; 1 point each)
Sediment grain sizeSediment Name Sedimentary Rock
| |
>256 mm| |boulder conglomerate
| |
| |
2-256 mm| |
| |
| |
0.062-2.0 mm| |
| |
| |
0.004-0.062 mm | |
| |
| | foliated
< 0.004 mm| |
| |
| |non-foliated
57. What is the "S-wave shadow zone," what is its significance, and why? (10 points)
58. What are the four MOST IMPORTANT elements that plants must be able to extract from soils? Which is the ONE of these four that is the ONLY plant nutrient that does not derive directly from chemical weathering of minerals? (10 points: 2 pts. each)
The four most important elements plants need to get from soils are:
The only one of these four that is NOT derived from chemical weathering of minerals is: