Geology 101 - Fall 2003
Exam #4
1. Draw a cross section of the Earth showing the different compositional layers. Make it reasonably close to scale.
2. How do we know that the Earth has the three main layers I asked you to sketch in question #1? We haven’t seen most of Earth’s interior, so why do we believe what we believe about it?
3. The seafloor has lots of mountains and valleys. Some of these features are listed below. What are they and how do they form?
a. deep ocean trenches
b. submarine canyons in the continental slope
c. rift valleys
d. seamounts
e. guyots
4. What is a turbidity current? What sort of sediment does a turbidity current produce, and what kind of rock(s) will the sediment become after lithification?
5. Why is there a depth limit for the deposition of limestones in oceans?
6. Generally seismic wave velocity increases as you go down in the Earth. However, at a depth of about 3000 km, P-wave velocity decreases abruptly. At this same depth, S-wave velocity goes to zero. Why?
7. What did Mohorovicic observe that led him to infer that there was a major change in composition at the base of the Earth’s crust? Be specific enough in your answer so that I know that you know what you are talking about!
8. The Black Hills of South Dakota are good examples of what type of structural feature? Describe the forces and movements involved in creating such a feature. Use a drawing if it would help.
9. Faults that are experiencing no active creep may be considered “safe.” Rebut or defend this statement.
10. How does the boundary between the crust and the mantle (Moho) differ from the boundary between the lithosphere and the asthenosphere?
Multiple Choice
1. Tensional forces may cause the formation of
a. anticlines
b. synclines
c. normal faults
d. thrust or reverse faults
e. all of the above
2. Strain (in geology-speak) refers to
a. any force that deforms a rock
b. any compressional force that deforms a rock
c. irreversible change in shape or size of a rock body
d. shearing or other forces that create transform faults
e. rock deformation that will “reverse” or become “undone” once force is removed
3. The difference between elastic deformation and plastic deformation is that
a. elastic deformation is not reversible
b. plastic deformation is not reversible
c. elastic deformation is brittle
d. plastic deformation never occurs
e. elastic deformation never occurs
4. __________ is the compass direction of a line produced by the intersection of an inclined rock layer or fault, with a horizontal plane.
a. plunge
b. dip
c. strike
d. trend
e. anticline
5. The Uinta Mountain Range (northeastern Utah) has been uplifted. Old rocks are exposed at the center, younger ones in “rings” around the outside. This sort of structure is related to the formation of a/an:
a. thrust fault
b. reverse fault
c. normal fault
d. anticline
e. syncline
6. Fault block mountains and horst & graben structures are characterized by __________.
a. thrust faults
b. reverse faults
c. normal faults
d. strike-slip faults
e. detachment faults
7. The San Andreas Fault is a classic example of a a. thrust fault
b. reverse fault
c. normal fault
d. strike-slip fault
e. detachment fault
8. The JOIDES Resolution was
a. the first “modern” marine research vessel in 1857
b. the first submersible capable of going down to the MOR
c. a new type of side scan sonar for making maps of the ocean floor
d. a new type of GPS/GIS unit used for making maps of the ocean floor
e. a research vessel that drilled holes in the ocean floor
9. The Ring of Fire is located
a. in Grand Forks
b. in northern Africa
c. in the Antarctic
d. around the Atlantic Ocean
e. around the Pacific Ocean
10. Pelagic sediments are
a. sands and associated sediments found in near shore environments
b. carbonate rich materials deposited on continental shelves
c. carbonate rich materials deposited on continental slopes, but that often slide into deeper water
d. clastic material deposited on continental shelves
e. deep marine sediment made of small stuff like plankton and clays
11. When we say an earthquake is “magnitude 7" we are using the
a. bathroom scale
b. Mercalli scale
c. Richter scale
d. Wadati-Benioff scale
e. fish scale
12. What is a general term that describes the composition of Earth’s mantle?
a. P-wave
b. tsunami
c. granitic
d. pelagic
e. ultramafic
13. The place underground where the energy to produce an earthquake is released is called the
a. epicenter
b. paracenter
c. target center
d. focus
e. transform fault
14. What is a tsunami?
a. an especially strong earthquake
b. a landslide triggered by an earthquake
c. a tidal wave triggered by an earthquake
d. a strong but unfelt earthquake
e. a not very strong earthquake that is easily felt
15. Around 1960, there was lots of money available so seismologists could set up seismographs. Why?
a. the economy was booming
b. John F. Kennedy was President
c. the National Science Foundation was created
d. Vine and Matthews confirmed seafloor spreading
e. the cold war
16. Some sections of the San Andreas fault exhibie a slow, gradual displacement known as __________.
a. elastic rebound
b. foreshocks
c. aftershocks
d. fault creep
e. stress
17. Deep focus earthquakes occur several hundred kilometers below ______________.
a. mountain ranges
b. transform faults
c. normal faults
d. subduction zones
e. mid ocean ridges
18. The wave amplitude (height) for an earthquake of magnitude 7 is _____________ compared to the wave amplitude for an earthquake of magnitude 6?
a. 1/7 = 14% greater
b. 1/6 = 17% greater
c. twice as large
d. 10 times larger
e. 30 times larger
19. The Dynamo Theory is a theory used to explain Earth’s
a. seismicity
b. heat flow
c. gravity
d. elastic rebound
e. magnetic field
20. Off the west coast of the United States, where does subduction take place today?
a. everywhere
b. nowhere
c. near southern California
d. near Mexico
e. near Washington and Oregon
21. The boundary between the crust and the mantle is the
a. P wave shadow zone
b. inner core
c. outer core
d. Benioff zone
e. Moho
22. How thick is the crust of the earth?
a. 0-2 km
b. 2-4 km
c. 0-10 km
d. 2-10 km
e. 0-70 km
23. The asthenosphere is part of the Earth’s
a. crust
b. mantle
c. outer core
d. inner core
e. lithosphere
24. The plates that float around causing oceans to open and close, etc., are part of Earth’s
a. crust
b. mantle
c. outer core
d. inner core
e. lithosphere
25. Which type of seismic wave does not travel through liquid?
a. P-wave
b. S-wave
c. surface wave
d. ocean wave
e. primary wave
26. Geologists and physicists believe the core of the Earth is mostly
a. quartz
b. nickel
c. carbon
d. magnesium
e. iron
27. Which of the following comprises the most volume?
a. crust
b. mantle
c. core
d. asthensphere
e. lithosphere
28. The most significant process that transfers heat through Earth’s mantle is __________.
a. radiation
b. convection
c. conduction
d. solifluction
e. subduction
29. When earthquake waves cross boundaries in the Earth where the Earth changes composition, the waves can
a. be reflected
b. be refracted
c. be attenuated (lose energy)
d. completely die out (if S waves)
e. all of the above
30. When an earthquake occurs, sesismic waves of various sorts travel in all directions. The fastest waves, which are the first generally to arrive at seismic stations, are
a. Love waves
b. Rayleigh waves
c. surface waves
d. S waves
e. P waves
31. What ocean floor features are associated with the oldest rocks?
a. subduction zones
b. transform faults
c. reverse faults
d. mid-ocean ridges
e. guyots
32. Where is new lithosphere being formed?
a. subduction zones
b. transform faults
c. reverse faults
d. mid-ocean ridges
e. guyots
33. Which of the following is a passive continental margin?
a. the west coast of South America
b. the Aleutian Islands
c. Hawaii
d. the Rocky Mountains
e. the east coast of the United States
34. The Earth’s crust is extremely thin or nonexistent
a. in the center of old continents
b. at active continental margins
c. at transform faults
d. at subduction zones
e. at mid ocean ridges
35. The type of stress that normally occurs at converging plate boundaries is:
a. compression
b. tension
c. strain
d. shearing
e. any of the above
36. Accretionary wedges form
a. on broad continental shelves
b. on continental rises
c. on passive continental margins
d. on active continental margins
e. all of the above are correct
37. “Sedimentary deposit on abyssal plain, generally located near the mouth of submarine canyons, that exhibits graded bedding.”
a. tsunami
b. sandstone
c. guyot
d. shale
e. turbidite
38. Why are abyssal plains more extensive on the floor of the Atlantic than on the floor of the Pacific?
a. the continental shelves around the Atlantic are larger
b. the continental shelves around the Atlantic are smaller
c. rift valley, trenches, submarine canyons, guyots and atolls are in the Pacific instead of abyssal plain
d. there is no subduction on the margins of the Pacific
e. there is no subduction on the margins of the Atlantic
39. The two principle types of marine sedimentary rocks are
a. shale and sandstone
b. limestone and sandstone
c. sandstone and mudstone
d. mudstone and shale
e. mudstone and limestone
40. The 1964 Good Friday Earthquake was one of the largest on record. It took place in
a. California
b. Missouri
c. Japan
d. Afghanistan
e. Alaska