## ES 10 -- The Earth Final Exam Practice Version Answer Sheet 15 March 1997

The correct answers are shown in bold face

1. What is a typical rate for seafloor spreading?
1. 50 m/yr
2. 5 m/yr
3. 50 mm/yr
4. 0 mm/yr

For more details, see Chapter 20 and Lecture 4

2. What causes ocean tides?
1. gravitational pull of the sun
2. gravitational pull of the moon
3. distribution of continents
4. gravitational pull of the sun and moon

For more details, see Chapter 17.

3. Which of these igneous rocks has the highest silica content?
1. diorite
2. andesite
3. granite
4. basalt

The order (low to high silica content) is basalt -> diorite/andesite -> granite.
For more details, see Chapter 4.

4. What is a guyot?
1. flat-topped seamount
2. low-lying coral-reef island
3. type of rock
4. small seamount

For more details, see Chapter 17 and Lecture 16.

5. What type of plate boundary is the San Andreas Fault?
1. subduction zone
3. transform fault
4. fracture zone

For more details, see Chapter 18 and 20.

6. What is the average elevation of the continents?
1. 8 m
2. 80 m
3. 800 m
4. 8000 m

For more details, see your notes from Lecture 22.

7. What is the average thickness of the oceanic crust?
1. 7 km
2. 70 km
3. 700 km
4. 7000 km

For more details, see Chapter 20.

8. The speed of sound in sea water is 1500 m/sec. What is the round-trip time of a sound pulse when the water depth is 3000 m?
1. 1 s
2. 2 s
3. 4 s
4. 8 s

It takes 2 seconds to go 3000 meters, if you are moving 1500 m/sec. So if you need to go 3000 meters down and then 3000 meters up, it takes a total of 4 seconds.

9. Where is the largest ice cap?
1. Iceland
2. Greenland
3. Antarctica
4. Australia

For more details, see Chapter 15 and Lecture 17.

10. What are the units of mass density?
1. m/s
2. tree/acre
3. w/m2
4. kg/m3

11. Where do the deepest earthquakes occur?
1. San Francisco
2. the core
3. subduction zone
4. transform faults

For more details, see Chapter 20 and Lecture 10.

12. Lithosphere is created at spreading ridges. Where is it destroyed?
1. transform faults
2. hot spots
3. deep ocean trenches
4. No, it is not destroyed. The earth grows in radius.

For more details, see Chapter 20 and Lecture 10.

13. Which type of plate boundary has mostly strike-slip faults?
2. continental margin
3. transform fault
4. subduction zone

For more details, see Chapters 10 and 20 and Lecture 10 and Lecture 12.

14. Which have the greatest velocities in rock?
1. surface waves
2. tsunami
3. primary waves (P-waves)
4. secondary waves (S-waves)

For more details, see Lecture 20

15. Which currents move sand and water parallel to the beach?
1. reflected
2. translational
3. longshore
4. ebb tide

For more details, see Chapter 17 and Lecture 18 (Brad Werner's lecture).

16. Which would prove that a coastline was emergent?
1. many bedrock islands
2. an elevated wave-cut terrace
3. a barrier island
4. an estuary

For more details, see Chapter 17 and Lecture 18.

17. What famous 19th century scientist proposed a basically correct theory of how atolls formed?
1. Newton
2. Hutton
3. Darwin
4. Lyell

For more details, see Chapter 17 and Lecture 16.

18. What is the best way to scientifically explain the hundreds of meters of coral limestone beneath most atolls?
1. sea level has fallen thousands of feet since the reef began to grow
2. the eroded volcano below the limestone rose thousands of feet after the limestone accumulated
3. the eroded volcano slowly sank as sea level remained steady or rose gradually
4. the volcano never reached the surface, allowing a very thick cap of coral limestones to accumulate

For more details, see Chapter 17 and Lecture 16.

19. On a typical seismogram, which waves will show the highest amplitudes?
1. P waves
2. S waves
3. surface waves
4. body waves

Don't worry about this question. It is deceptive, and as stated, the only correct answer is ``e -- it depends''.

20. The Marina District in San Francisco was heavily damaged in the 1906 and 1989 quakes. Why?
1. the epicenters of both quakes were right under the district
2. the area is built on consolidated rock, causing the shaking to be amplified
3. liquefaction and other foundation failures were common
4. shaking was not any more extensive than elsewhere in the city, but the whole district burned following each quake

For more details, see Lecture 20

21. During the glacial period, sea level:
1. rises
2. falls
3. remains at the same level

For more details, see Chapter 15 and Lecture 17.

22. The oldest basalts of the oceanic crust are approximately 160 million years old. Where would you go to drill samples of these old oceanic basalts?
1. at the crest of the East Pacific mid-ocean ridge
2. on the oceanic side of the Mariana deep ocean trench
3. under Iceland
4. off the coast of our nation's capital (Washington, D.C.)

For more details, see Chapter 20 and Lecture 10.

23. What does NOT happen as the oceanic lithosphere ages?
1. seafloor depth increases
2. lithospheric thickness increases
3. magnetic anomaly increases
4. sediments accumulate on the seafloor

For more details, see Chapter 20.

24. How do we know that the Rose Canyon Fault has ruptured during the past 10,000 years?
1. earthquakes are common along the fault today
2. a trench across the fault shows offsets in sedimentary layers
3. the fault follows Interstate 5
4. all faults in California are active

For more details, see Lecture 21.

25. How many seismic stations are needed to locate an earthquake?
1. 1
2. 2
3. at least 3
4. at least 10

For more details, see Lecture 20 and the answers to Homework 5.

26. What is the circumference of the Earth (i.e. 2 times the radius, where = 3.14)?
1. 400 km
2. 4,000 km
3. 40,000 km
4. 400,000 km

For more details, see Lecture 3 and Lecture 22.

27. These tides create the largest daily tidal range.
1. spring tides
2. solar tides
3. neap tides
4. lunar tides

For more details, see Chapter 17.

28. Which of the following is a depositional feature?
1. wave-cut cliffs
2. sea stack
3. spit
4. sea arch

For more details, see Chapter 17.

29. _______ is a deposit which formed by the downslope movement of dense, sediment-laden water. It exhibits graded bedding and is found in submarine canyons.
1. turbidite
2. conglomerate
3. ophiolite
4. terrigenous sediment

For more details, see Chapter 17 and Lecture 16.

30. What was Pangaea? When did it form and when did it break apart?
1. a supersize ocean basin that opened in the Triassic and closed in the Palaeocene
2. a supersize Precambrian shield area of Africa and South America that broke apart early in the Proterozic
3. the huge mountain range formed when Africa pushes northward into Europe in Eocene time
4. the supercontinent that formed in the late Palaeozoic and broke apart in Triassic time

For more details, see Chapter 20.

31. Where is the continental rise?
1. at the top of the continental slope
2. at the seaward edge of a deep ocean trench
3. between the edge of the abyssal plain and the continental slope
4. at the top of a mid-ocean ridge

For more details, see Chapter 17 and Lecture 16.

32. What term denotes the vast, deep, flat, sediment-covered parts of the ocean basin? (Hint: They make up the majority of the ocean basins.)
1. continental margins
2. abyssal plains
3. submarine canyons
4. trenches

For more details, see Chapter 17 and Lecture 16.

33. Which best describes the boundary between northern India and Eurasia?
1. two continental plates are converging
2. two continental plates are diverging
3. an oceanic plate is diverging from a continental plate
4. two continental plates are sliding past each other along the northern India transform fault

For more details, see Chapter 20.

34. Volcanic island arcs are associated with which plate boundary?
1. convergent, passive trailing margins of two continental plates
2. divergent, two oceanic plates
3. transform, an oceanic plate and a continental plate
4. convergent, two oceanic plates

For more details, see Chapter 20.

35. The concept that rocks of the crust and upper mantle are floating in gravitational balance is known as:
1. elastic rebound
2. isotropy
3. uniformitarianism
4. isostasy

For more details, see Chapter 19.

36. Which one describes a normal fault?
1. the hanging wall block below an inclined fault plane moves downward relative to the other block
2. the footwall block below an inclined fault plate moves downward relative to the other block
3. the hanging wall block above an inclined fault plane moves downward relative to the other block
4. the footwall block above an inclined fault plane moves upward relative to the other block

For more details, see Chapter 10 and Lecture 12.

37. Which area and type of terrain result from active or recently-active normal faulting?
1. the Basin and Range, eastern USA
2. the Valley and Ridge, western USA
3. the Valley and Ridge, eastern USA
4. the Basin and Range, western USA

For more details, see Chapter 10 and Lecture 12.

38. Which one is not a very long-lived radioactive isotope?
1. 238U
2. 40K
3. 87Rb
4. 14C

For more details, see Chapter 9 and Lecture 13.

39. What is an unconformity?
1. a buried fault or fracture with older rocks above and younger rocks below
2. a buried surface of erosion separating younger strata above from older strata below
3. a buried fault or fracture with younger strata above and older strata below
4. the contact between a cross-cutting pluton and sedimentary rocks

For more details, see Chapter 10 and Lecture 12.

40. For nos 40-43, refer to Figure 1. Match the following lithospheric plates (indicated by a number) with the corresponding letter choice.
1. African Plate
2. Nazca Plate
3. Pacific Plate
4. Eurasian Plate
5. Antarctic Plate

1. Of the original starting amount of radioactive parent isotope, 25% remains and 75% has decayed. How many half-lives have passed?
1. 0.5
2. 1.5
3. 2
4. 3

For more details, see Chapter 9 and Lecture 13.

2. Which one is not a process of radioactive decay?
1. electron capture
2. alpha emission
3. delta capture
4. beta emission

Don't worry about this question. We never covered it, and neither does the book.

3. Which statement applies to an anticline?
1. a fault in which strata dip away from the axis
2. erosion exposes the oldest strata along the axial part of the fold
3. a bowl-shaped depression
4. a fold in which the strata dip toward the axis

For more details, see Chapter 10 and Lecture 12.

4. According to geologists, the continental crust is best described as:
1. 10 km thick, granitic composition
2. 20-60 km thick, basaltic composition
3. 20-60 km thick, granitic composition
4. 10 km thick, basaltic composition

For more details, see Chapter 19.

5. The most common detrital sedimentary rock is?
1. sandstone
2. slate
3. siltstone
4. shale

You could also argue for shale, because your book puts siltstone and shale together in one bin...

For more details, see Chapter 7.

6. Today, we are living in the _______ Era.
1. Cenozoic
2. Proterozoic
3. Mesozoic
4. Palaeozoic

For more details, see Chapter 9 and Lecture 13.

7. The most aboundant element in Earth's atmosphere is:
1. argon
2. carbon dioxide
3. oxygen
4. nitrogen

For more details, see Lecture 19.

Figure 1. World Plate Map