Download practice exam #1

EXAM #3-PRACTICE
GEOL 131
FALL 2015
GEOLOGIC TIME
1. Refer to your geologic time scale, and list the eon, era, period, and epoch in which we are currently
living.
a. Eon: ______________________
b. Era: ______________________
c. Period: _____________________
d. Epoch: ______________________
2. Why is relatively little detail known to geologists about the time period called the Precambrian?
(circle two answers)
a. The Precambrian only makes up a small fraction of Earth history
b. An asteroid impact destroyed most of the Precambrian rock record
c. Nothing lived during the Precambrian, so there is no fossil record
d. Organisms that lived during that time had no hard parts
e. More of the geologic record of the Precambrian has been destroyed compared to more recent
time periods
3. Name a significant evolutionary event that took place during the Paleozoic Era, one during the
Mesozoic, and one during the Cenozoic (do not use the mass extinctions at the end of the Paleozoic
and Mesozoic Eras).
Paleozoic: __________________________________________________________
Mesozoic: __________________________________________________________
Cenozoic: __________________________________________________________
4.
The end-Paleozoic mass extinction was likely caused by an asteroid impact. TRUE or FALSE
5. The evolutionary phenomenon in which a few species that survive a mass extinction branch out into
many new species is called _______________________________.
1
6. What is the most important difference between relative dating and radiometric dating?
_________________________________________________________________________________
_________________________________________________________________________________
7. Match the principles of relative dating given below with the correct definitions.
a. Superposition
b. Inclusions
c. Cross-cutting relations
If pieces of A are found within B, A is older _____
If A is below B, A is older
_____
If A cuts through B, B is older
_____
8. Put the geologic features in the diagram below in the correct sequence, with oldest at the bottom.
Write the letters on the lines provided to the left of the figure. Ignore the black boxes. In the white
box, give the name of the type of unconformity represented by the red line.
2
9. There are two figures below. The left-hand figure shows a hypothetical rock layer with two fossil
species present (shown by symbols). The right-hand figure is a fossil range chart, showing the
ranges of several fossil species.
By looking at which fossil species are present (and which are not present) in the rock layer, and
comparing them to the fossil range chart, determine the youngest possible relative age for the rock
layer. Draw a horizontal line on the fossil range chart indicating this age.
FOSSIL RANGE CHART
ROCK LAYER
10. Define the term half-life. _________________________________________________
____________________________________________________________________________
11. Radioactivity is
a. Spontaneous changes in the nucleus of an atom
b. A process that happens at a predictable rate
c. The change of a parent atom into a daughter atom
d. All of the above
e. A and B
f. B and C
g. A and C
12. Why is it very difficult to use radiometric dating on sedimentary rocks?
a. Mineral grains never contain radioactive material
b. Sedimentary rocks contain cement, which is highly radioactive and interferes with the dating
process
c. Mineral grains come from older source rocks
d. The question is false; it is actually easiest to obtain a radiometric date from sedimentary
rocks
3
13. If a mineral is found to contain 25% uranium-235, how many half-lives of U-235 have elapsed since
the mineral formed?
Half-lives elapsed: __________
14. How old is the mineral from the previous question? ________________ years (you do not need to
show calculations)
PLATE TECTONICS
15. Why was Alfred Wegener’s continental drift hypothesis rejected by most scientists of his time?
_______________________________________________________________________
_______________________________________________________________________
16. Based on evidence he collected during extensive scientific travels, Wegener proposed that all of the
modern continents had once been joined into a supercontinent called
a. Panthalassia
b. Panoplia
c. Pantera
d. Pangaea
e. Pangyratia
17. When other scientists objected to the continental drift hypothesis, what did Wegener propose in an
attempt to resolve these objections?
_______________________________________________________________________
_______________________________________________________________________
18. The outermost layer of the Earth, as defined by the behavior of seismic waves as they pass through
the planet, is called the
a. Asthenosphere
b. Mesosphere
c. Crust
d. Mantle
e. Lithosphere
19. Continental lithosphere is dense enough to subduct into the mantle, but oceanic lithosphere is not.
TRUE or FALSE
20. At a divergent plate boundary, crust is being
a. Destroyed
b. Created
c. Neither
4
21. Put the following stages in creation of a new divergent boundary in the correct order by writing 1, 2,
3, or 4 next to each.
a. Stretching and thinning of continental lithosphere
_____
b. Widening into a mature ocean basin
_____
c. Formation of a narrow seaway
_____
d. Upward pushing on continental lithosphere by mantle magma _____
22. Match each type of convergent plate boundary with the correct definition:
a. Oceanic-oceanic
Subduction, formation of continental volcanic arc
_____
b. Oceanic-continental
No subduction; uplift of mountain ranges
_____
c. Continental-continental
Subduction, formation of volcanic island arc
_____
23. Most transform plate boundaries are closely associated with divergent boundaries. TRUE or FALSE
24. Fill in the blanks: The further away from a divergent boundary an ocean drill core is collected, the
__________ the sediment will be and the ____________ the crustal rock will be.
25. A hypothetical chain of volcanic islands produced by a hot spot is sampled and radiometrically dated.
The chain is oriented east-west. The youngest island is found to be at the west end, and the oldest on
the east end. In what direction is the plate carrying the islands moving? _____________
26. In order to use hot spot volcanic chains to calculate average rates of plate tectonic movement,
geologists need what two pieces of information? (Circle two answers.)
a.
b.
c.
d.
e.
The absolute ages of the volcanoes, in years
The composition of the volcanic rocks
The relative ages of the volcanoes (what order they formed in)
The depth of the ocean along the chain
The length of the chain
5
27. Examine the diagram of paleomagnetic striping on ocean crust below. How many time periods of
reversed magnetic polarity are recorded by this ocean crust? (Light-colored stripes are reversed
polarity) _______
28. In one or two sentences, describe what happens during slab pull. ___________________
______________________________________________________________________________
______________________________________________________________________________
CRUSTAL DEFORMATION
29. Which of the following types of deformation is temporary (circle one)?
a. Ductile
b. Brittle
c. Elastic
d. None of these is temporary
30. A rock’s capacity for absorbing temporary deformation is called its _____________________.
31. The hotter a rock is, the more likely it is to deform in ductile fashion. TRUE or FALSE
6
32. Match each fold listed below to the correct figure.
a. Anticline
b. Syncline
c. Monocline
________________
________________
_________________
33. In each of the photos above, draw a line indicating the approximate location of the fold axis (or axes).
34. The figures below show map view perspectives of two different folds, with the relative ages of the
layers. What types of folds are these?
oldest
youngest
youngest
youngest
oldest
Fold type: ____________
Fold type: ____________
7
35. A fold with one limb dipping at an angle greater than 90 degrees is called
a.
b.
c.
d.
Recumbent
Overturned
Symmetrical
Asymmetrical
36. On the fault below, label the hanging wall and the footwall. The red line indicates the location of the
fault.
8
37. Match each fault type listed with the correct figure.
a. Normal
b. Reverse
c. Thrust
d. Left-lateral strike-slip
e. Right-lateral strike-slip
CROSS-SECTIONS
______
______
______
MAP VIEWS
____
_____
38. Match each fault type with the kind of stress that produces it.
a. Strike-slip
Tensional
_____
b. Reverse
Shear
_____
c. Normal
Compressional_____
THE OCEAN FLOOR
39. Label the map below with the four major ocean basins.
9
40. What ocean floor mapping method penetrates sediment cover and reveals the bedrock underneath?
41. If a ship emits a ping and the ping returns 5 seconds later, how deep is the ocean beneath the ship?
(Speed of sound in water is 1500 meters/second)
42. Label the following diagram of a passive continental margin.
43. The continental rise portion of a passive margin consists of _______________________________.
44. Active margins are characterized by all of the following except: (circle one answer)
a. Wide continental shelves
b. Earthquakes
c. Volcanism
d. Mountainous coastlines
e. Tectonic plate subduction
45. Most of a typical deep ocean floor is taken up by the _______________________, which is very flat
due to thick sediment cover.
10
46. The image below shows the Hawaiian islands and the Emperor Seamount chain. These are all
examples of what feature of the deep ocean floor? _____________________
47. In the same image, there is a feature called the Aleutian Trench. What geologic process created this
feature? ______________________
48. Oceanic ridges are places where two tectonic plates are ___________________.
49. In this illustration of the central part of an oceanic ridge, draw arrows indicating the direction of
motion of both tectonic plates. Also, label the rift valley and one of the fault blocks.
50. Explain why oceanic ridges are elevated features. ______________________________________
51. Oceanic ridges are formed by the same process that creates which type of tectonic plate boundary?
11