Geology 111G, Section 3 Name:____________________
Spring 2003
EXAM 2
Multiple Choice (50 points; 2
points each). Circle the letter of
the correct answer.
1. Which of the following rocks is not a clastic sedimentary rock?
a) Conglomerate;
b) Limestone;
c) Sandstone;
d) Shale.
2. Daughter isotopes are
a) Formed during radioactive decay.
b) Destroyed during radioactive decay.
c) Extremely rare in most radio active
reactions.
d) Future mother isotopes.
3. The principle of superposition states
that
a) Youngest strata occur at the top of a
layered succession, oldest at the bottom.
b) A rock is younger than any rock it cuts
across.
c) Fossil animals and plants have succeeded
one another in a discernible order.
d) Most strata are deposited more or less
parallel to the surface of the earth.
4. Which of the following factors is
probably not important in the metamorphic environment?
a) Heat.
b) Pressure.
c) Fluids.
d) Weathering.
5. The general term for layering in rock
sequences, particularly sedimentary sequences, is:
a) Strata.
b) Deposits.
c) Foliation.
d) Banding.
6. A dip-slip fault in which the
hanging-wall block has moved downward relative to the footwall block is termed
a ______________ fault.
a) Right-lateral.
b) Left-lateral.
c) Active.
d)
7. A dip-slip fault in which the
hanging-wall block has moved upward relative to the footwall block is termed a
______________ fault.
a)
b) Reverse.
c) Compressive.
d) Extensional.
8. A strike-slip fault in which the
opposite block appears to have moved to the right is termed a:
a) Right-lateral fault.
b) Left-lateral fault.
c) Dip-slip fault.
d) Ambiguous fault.
9. Which of the following is an example of
a geologic period?
a) Jurassic.
b) Mesozoic.
c) Cenozoic.
d) Phanerozoic.
10. Mechanical weathering is
the_______________ of existing rocks.
a) Disintegration.
b) Decomposition.
c) Removal.
d) Melting.
11. Hornfels is
which of the following?
a) A hard, splintery metamorphosed
siltstone that results from contact metamorphism.
b) A metamorphosed limestone.
c) A weakly
metamorphosed shale with a slight foliation.
d) A metamorphosed quartz sandstone.
12. All chemical weathering reactions
involve the following compound:
a) CO2, carbon dioxide.
b) H2O, water.
c) SO2, sulfur dioxide.
d) H2S, hydrogen sulfide.
13. Which of the following Earth
materials would be most appropriately datedusing the
Potassium-Argon (K-Ar) dating technique which
utilizes the decay of a radiogenic isotope of potassium to argon gas, that is trapped in the crystallattice
of a mineral following cooling?
a) Organic compounds such as charcoal,
wood, textiles;
b) A conglomerate;
c) Rhyolite with biotite and potassium feldspar;
d) Marble.
14. Two
changes that affect sedimentary rocks during diagenesis
are the following:
a) compaction of grains and cementation at less
than 200oC;
b) compaction of grains and cementation at more
than 200oC;
c) recrystallization
and reorientation of mica grains in the presence of elevated temperature and pressure;
d) deposition and formation of primary sedimentary
structures
15. Chemical weathering can best be considered as
___________ of rocks in to new mineral types.
a)
Disintegration;
b)
Decomposition;
c)
Shrinkage;
d)
Deconvolution.
16. A
major surface of erosion and/or non deposition that separates two rock masses
is termed a(n):
a)
Hiatus;
b)
Bedding plane;
c)
Event;
d)
Unconformity.
17. A sedimentary rock composed of particles
of quartz between 1/16th and 2 mm in diameter (i.e., sand grains) is referred
to as:
a) Conglomerate;
b) Sandstone;
c) Siltstone;
d) Mudstone.
18. The
Geologic Time Scale is:
a)
A measuring
device for assessing the length of geologic periods;
b)
A sequential
arrangement of formally defined geologic periods;
c)
A standard rate
of radioactive decay exhibited by 235U;
d)
A balance for
weighing minerals with radioactive elements.
19. Which of the following rocks is a metamorphosed
limestone?
a)
marble;
b)
quartzite;
c)
hornfels;
d)
conglomerate.
20. The reaction shown below is an example
of
a)
hydrolysis;
b)
oxidation;
c)
dissolution;
d)
none of the above.
2Fe3O4+ 3H2O = 3Fe2O3 + 2H2O + 2H+
magnetite hematite
21. The principle of cross-cutting
relationships states that:
a) Youngest strata occur at the top of a
succession.
b) A rock is younger than any rock it cuts
across.
c) Fossil animals and plants have ucceeded one another in a discernible order.
d) Most strata are deposited more or less parallel to the surface of the earth.
22.
Techniques employed to determine the age of radioactive isotopes
contained in minerals fall under the category of ____________ dating
techniques.
a. Radiometric.
b. Relative.
c. Deterministic.
d. Decay.
23. One type of division of the Geologic
Time Scale is characterized by continuity of life forms during that
interval. Examples are the
Paleozoic, Mesozoic and Cenozoic. What is the name of this division of geologic
time?
a) Eon.
b) Era.
c) Period.
d) Stage.
24. The force per unit area applied to a
rock is termed ____________. If
this is strong enough, it will cause the rock to change shape.
a) Stress;
b) Strain;
c) Strike;
d) Faulting.
25. The term half life, when applied to
radioactivity, refers to
a) The time required for the number of
parent isotopes in a sample to be reduced by 1/2.
b) Half the age of the earth.
c) The age of the oldest one-half of aradioactive sample.
d) The age of a sample when exactly hal fof the atoms are parent
isotope and half are daughter isotope.
Short Answers (10 points;
points as indicated)
26. Three types of folds were described in
class. Name and describe (using
sketches if you wish) two types of folds. (4 points total, 1 each for name and1
each for description/sketch).
27. Relative age. Answer the following questions using the
relationships depicted in the rock exposure above. For each answer, name the stratigraphic principle that you used to arrive at your
answer. (6 points total)
a. What
formation is oldest? Which
principle? (2 points)
b. Is the basalt dike older or younger than the shale formation? Which principle? (2 points)
c. What
formation is the youngest? Which
principle? (2 points)
Extra
credit: In c above, you actually
invoked two principles at the same time to answer the question correctly. What are the two principles and howwere they used (i.e., specifically explain how the
principles are used in this case)? (4 points)
Matching (10Points)
28. On the following plate tectonic sketch,
there are 5 boxes. Above there are
the names of 5 metamorphic rock types, or metamorphic facies. Consider the temperature and pressure
environment of each box and place the letter of the box next to the appropriate
rock type below. When in doubt, use the best answer for a given type of
metamorphism. Five boxes, five
letters, with no repeats, no double answers. Three of these that are high temp are really
determined by the pressure environment.
Pick the best boxes for the high-grade rocks based on how deep in the
crust they are.
1. Blueschist _________
2. Greenschist _________
3. Granulite _________
4. Amphibolite _________
5. Hornfels _________
Term Recognition (30 points; 3 points each). Fill in the missing term (the blank)using one of the terms from the following list:
blueschist directed greenschist
amphibolite plastic metamorphism
fossil compression stratigraphy
soil overturned upright
foliation confining greenschist
extension limestone dolostone
elastic conglomerate sandstone
granulite amphibolite hornfels
contact regional burial
29. Thermally altered rocks adjacent to a pluton are said to have experienced ____________
metamorphism.
30.A residue formed at the surface of the earth by
modification of bedrock by weathering, either by removal or addition of
minerals, is termed ____________.
31. A succession of upside-down sedimentary
beds is said to be __________.
32. Subduction of
cool oceanic crust to great depth may give rise to the following type of rock,
which indicates low temperature, but high-pressure metamorphism. _____________
33. The study of layered rocks is
termed________________.
34. The alignment of platy minerals in
metamorphic rocks is termed _____________.
35. The alignment of platy minerals in a
metamorphic rock is formed by exposure of the rock to ____________ pressure.
36. The set of processes by which rocks
undergo a change in mineralogy, texture, or both in the presence of pressure
and heat in excess of 200o C is termed _________________________.
37.Recoverable strain is referred to as ____________
strain. In this
case an object returns to its original shape upon removal of stress.
38. A squeezing stress is
called_______________.
