EXAMPLE!!!!!!!!

EPS 101 PHYSICAL GEOLOGY , Section 001

FINAL (FOURTH) EXAMINATION, Spring, 1997, May 14 1997

NAME: _____________________________ SSN____________________________

Please note that this exam consists of three parts. It is considerably shorter than previous examinations; nonetheless you still have fully two hours to complete the examination.. Please read each question thoroughly and take your time. After that, have a rewarding summer. As you take this, I may or may not be in the field. I’ll be back on Friday and will finish my component of the grading; make certain I have your papers no later than noon on Saturday of graduation. Final grades should be posted by the following Monday.

I. The “Anatomy” of an Convergent plate margin or “Orogenic” Belt. This long answer question is mandatory. We have referred to mountain or orogenic belts several times during the semester. Below, please sketch out the essential elements of an orogenic belt along the margin of a craton. Label the four principal components of an orogenic belt on your diagram. For TWO of these components, describe the types of rocks found and geologic structures formed. Clearly, the more detail provided, the better. You might, for example, show where you would expect to find earthquakes forming, where magmatism of different types would occur, where sedimentary rocks of different types would be found, etc. etc. (15 points).

II. Relatively short answer questions. Note!!! Use sketches (labeled) where appropriate.

1. The Cretaceous Period, between about 135 and 64.5 million years ago, was a particularly important time in the geologic evolution of western North America and in particular the western United States. Describe two different “events” or processes happening during the Cretaceous that were important in shaping the western United States. Hint, why does the deformed region of the western U.S. stretch from the western borderland of California to the Front Range of Colorado? (8 points).

2. Describe the depositional environment of a relatively low-energy (low grade) river system, like the Rio Grande at the latitude of Albuquerque. Where is the coarsest sediment transported? What happens during flood stage (assuming the Cochiti Dam breaks!). How would an increase in the activity of normal faulting at the front of the Sandia Mountains affect the Rio Grande? (8 points).

3. What is the San Andreas fault? What kind of plate boundary does it represent? Why is this feature of such great societal concern? (4 points)

4. Over the past decade or so, geoscientists have begun to learn more and more about cause/effect associations between numerous different processes affecting our planet. One example emphasized in the course was the relation among tectonism (mountain building), climate, and weathering. For example, workers now believe that the collision of India with Asia had tremendous affects on the earth's climate, leading to an overall decrease in earth temperature at about 8 to 7 myr ago. Using the Sandia Mountains as a microcosm of the surface of our planet, what would you predict to happen if the climate became, overall, colder and moister, for a prolonged period of time? Explain. (4 points).

5. The elevation of the abyssal ocean floor decreases, relatively smoothly, with distance away from a mid-ocean ridge spreading center. Why is this? If the rate of spreading at a mid-ocean ridge were to increase, what might this do for the relative yet global (eustatic) level of the sea floor? How might this phenomenon be used to explain disconformites in the continental stratigraphic record? (4 points).

6. We discussed several aspects of the geology of the Sandia Mountains and vicinity during the semester. List and describe three important geologic features which are well-represented by our "back-drop" to the east. Hint, why are the Sandia Mountains here? (6 points).

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7. Food for thought question (but you have all the basics to answer it!!!). For several decades since its “discovery” by geoscientists, Meteor Crater in north-central Arizona was not necessarily considered the result of a young meteorite impact. What else could it have been? What kinds of evidence would you look for to prove the origin of the feature, and why? (4 points).

8. What are the three general types of rocks? For each general type, give a specific example and describe very briefly how it formed. (6 points).

9. Intuition-type question. Although we never got around to a detailed discussion of it, the WIPP “site” in southeast New Mexico is located in Permian (upper Paleozoic) sedimentary rocks, principally a thick sequence of salt several thousands of feet below the earth’s surface. What does the presence of a thick sequence of salt deposits imply? What could you imagine to be a seemingly positive attribute (geologic in character!!!!, of course) of the WIPP site as a location for storage of low-level nuclear waste? (5 points).

10. During the Cenozoic Era (beginning about 64.5 million years ago) , the western United States was shaped by a number of processes. One in particular was the inferred “collapse” of a continental crust that was overthickened by earlier periods of compression. What happened as a result of this collapse? What kinds of features and structures were produced? Where were they produced? (4 points)

11. The geomagnetic polarity time scale was developed by measuring the magnetic polarity of well-dated rocks, principally of volcanic and sedimentary origin. Of what importance was the geomagnetic polarity time scale in understanding the pattern of marine magnetic anomalies associated with mid-ocean ridges? How long ago (roughly) did geoscientists “crack the nut” of understanding the importance of mid-ocean ridges?

12. What did you like to learn about the most in this course? Why? (8 points)

13. An aquifer is usually a material with high porosity and permeability. What is meant by a “recharge” area for an aquifer? Why are these important? (4 points)

14. Describe the overall geology of the Albuquerque-Belen “basin”. In this description, try to answer the following concerns: of what larger feature is the basin a part?; when did the basin form?; what kinds of sedimentary rocks are associated with basin development?; what kinds of structures are associated with the basin?; why MUST we be concerned with the manner in which the area obtains its water supply? (5 points)

Part Three is on back of this page!!!!!

Part III. Geologic Features, Matching (note that in each case you are to match a location with a process) (10 points)

1._______ Albuquerque Volcanoes a. oceanic-continental convergence

2._______ Mount St. Helens b. example of a high-angle reverse fault,

3._______ Atlantic Ocean c. formed over the past 200 My, by sea floor spreading

4. ______ Rio Grande

5._______ western Wyoming fold/thrust belt d. artificial accumulation of large quantities of crystals, particularly

6._______ Santa Fe quartz, thought to be useful for healing purposes

e. stable, continent interior

7._______ Kansas

8._______ Jemez Mountains f. continent/continent collision

9._______ Himalayas

10.______ San Andreas fault g. back-arc compression

11. ______ Albuquerque NE heights

12.______ Sandia Mountains h. flows south within a continental rift

13.______ San Juan Basin

14.______ Glen Canyon Dam i. rift-related mafic magmatism

15.______ Estancia Basin, east of Sandias

16.______ Golden, CO j. surface expression of an active hot spot

17.______ Andes Mountains

18.______ Yellowstone k. dextral strike-slip fault

19.______ Shiprock, NM l. presently active, magmatic arc volcano

20. _____ Nacimiento Mountains m. basin formed beginning in late Cretaceous time

n. source of the Bandelier ash-flow tuffs

o. footwall uplift of a west-dipping normal fault system

p. home of Coors Ceramics, made from high-purity volcanic ash preserved in Cretaceous strata nearby,

q. surface formed on large alluvial fan system

r. a glacial maximum lake some 20,000 years ago

s. eroded volcanic neck

t. forming Lake Powell, rapidly filling with detritus, and soon to break

HAVE A GREATSUMMER !!!!!!!!!!