Geology 101: Introduction to Geology
Exam #2 

1. Which response has rocks in the correct order from (left to right) low-grade and fine grain size to high-grade and coarse grain size?
a. phyllite=>slate=>schist
b. slate=>phyllite=>schist
c. schist=>slate=>phyllite
d. slate=>schist=>phyllite
e. gneiss=>slate=>phyllite

2. If a metamorphic rock contains lots of carbonate minerals, what was it before it was metamorphosed?
a. quartzite
b. limestone or dolostone
c. shale or mudstone
d. a plutonic rock
e. beer

3. Which of the following is a foliated rock composed of alternating bands of light and dark silicate minerals?
a. schist
b. hornfels
c. gneiss
d. quartzite
e. beer

4. . Which of the following types of rocks can become metamorphic rocks?
a. sedimentary rocks only
b. igneous rocks only
c. sedimentary or igneous rocks only
d. sedimentary or metamorphic rocks only
e. sedimentary, igneous, or metamorphic rocks

5. Schist can be distinguished from other metamorphic rocks by:
a. its reaction to hydrochloric acid
b. its dark and light mineral bands
c. its metallic sheen
d. its slaty cleavage
e. its large flakes of aligned micas

6. Which low-grade metamorphic rock, composed of extremely fine-sized mica and other mineral grains, typically exhibits well-developed rock cleavage?
a. schist
b. slate
c. quartzite
d. hornfels
e. gneiss

7. Which of these descriptions best describes the conditions of contact metamorphism?
a. pressures are high; deep in the Earth; heat comes from inside Earth
b. pressures are low; upper part of crust; heat comes from nearby magma
c. depths are shallow, but pressures and temperatures are so high that rocks begin to melt
d. heat and pressure come from shearing and faulting along major fault zones
e. short and sudden periods of intense pressure at varying temperature

8. Which metamorphic rock is texturally between a slate and a schist?
a. quartzite
b. phyllite
c. breccia
d. gneiss
e. sandstone

9. The geothermal gradient describes how:
a. pressure increases with depth within the Earth
b. magma becomes more mafic with depth within the Earth
c. water content increases with depth within the Earth
d. temperature increases with depth within the Earth
e. migmatites form

10. Regional metamorphism generally occurs
a. when a rock is near or touching a pluton
b. along a fault zone
c. at the site of a meteor impact
d. in mountain belts during mountain building
e. after midnight and before dawn

11. If a metamorphic rock is metamorphosed to become a gneiss, and then is heated even more, there is a good chance it will become a
a. schist
b. garnet
c. hydrothermal solution
d. aureole
e. migmatite

12. In the centers of old continents are relatively flat areas of metamorphic rocks and associated igneous plutons called:
a. lopoliths
b. aureoles
c. formations
d. migmatites
e. shields


Consider the drawing above when you answer the next two questions.

13. Which is the youngest rock shown?
a. the layer labeled shale (or the stuff above it if it is rock)
b. the layer labeled sandstone
c. the unit labeled Dike B
d. the unit labeled Dike A
e. the bottommost layer of rock (labeled E)

14. Which is the oldest rock shown?
a. the layer labeled shale (or the stuff above it if it is rock)
b. the layer labeled sandstone
c. the unit labeled Dike B
d. the unit labeled Dike A
e. the bottommost layer of rock (labeled E)

15. Carbon-12 and carbon-14 are two different isotopes of carbon. The difference between them is that their atoms contain a different number of _____________________.
a. electrons
b. klingons
c. protons
d. ions
e. neutrons

16. Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content.
a. principle of fossil succession
b. principle of superposition
c. principle of crosscutting relationships
d. principle of original horizontality
e. principle of inclusions

17. Steve and Skunky:
a. two Grand Canyon geologists
b. names of hypothetical fossils
c. names of the two fathers of geological time
d. narrators of the film on sedimentary rocks
e. beer

18. When you observe an outcrop of steeply inclined sedimentary layers, what principle allows you to assume that the beds were tilted after they were deposited?
a. principle of fossil succession
b. principle of superposition
c. principle of crosscutting relationships
d. principle of original horizontality
e. principle of inclusions

19. The Earth is about ____ years old?
a. 4.5 thousand
b. 4.5 million
c. 4.5 billion
d. 4.5 trillion
e. 4.5 gazillion

20. In general, rocks exposed in the cores of mountain ranges are ________ when compared to surrounding rocks.
a. quite old b. quite young

21. The half life of uranium-238 is 4.5 billion years. This means that if we start with 100 atoms of uranium-238, we will have ___ atoms left after 9 billion years (two half lives):
a. 100
b. 75
c. 50
d. 25
e. 0

22. What may account for the fact that we don't have a detailed time scale for the Precambrian?
a. Precambrian rocks are not found at the surface in most parts of the Earth
b. there are not many fossils associated with Precambrian rocks
c. many Precambrian rocks were affected by metamorphism
d. we just don't know lots of things about rocks that old
e. all of the above

23. In general, chemical weathering would occur most rapidly in a:
a. cool, moist climate
b. cool, dry climate
c. warm, moist climate
d. warm, dry climate
e. area with lots of freezing days

24. Mechanical weathering can:
a. change the internal composition of minerals.
b. transport rock and mineral fragments to different locations
c. convert particular minerals into more stable forms
d. change the size and shape of rock structures
e. cause small rock fragments to combine to form larger rocks

25. Which of the following is the least stable due to weathering at the Earths surface?
a. quartz
b. clay
c. olivine or pyroxene
d. water
e. calcite

26. Unloading, thermal expansion, plants and critters, ice wedging and gravity can all cause
a. mechanical weathering
b. solifluction
c. hallucination
d. hydrolysis
e. oxidation

27. How is carbonic acid formed in nature?
a. when trees and other plants respire
b. when basalt dissolves in water
c. when limestone is precipitated
d. by dissolution of granite
e. when CO₂ dissolves in water

28. Heat speeds up a chemical reaction, so why does chemical weathering proceed very slowly in a desert?
a. deserts are not hot enough
b. deserts are not dry enough
c. deserts are not sandy enough
d. deserts are not cold enough
e. deserts are not wet enough

29. After deposition a sediment may change composition, be compacted, recrystallize, or be affected by organic activity during
a. lithification
b. crystallization
c. melting
d. stratification
e. diagenesis

30. Which of the following rocks is NOT (in general) a type of detrital sedimentary rock
a. conglomerate
b. breccia
c. limestone
d. sandstone
e. mudstone

31. Sedimentary structures such as graded bedding, cross-bedding, and ripple marks occur:
a. before both deposition and lithification
b. during or after deposition but before lithification
c. after lithification
d. during any of the above stages
e. during diagenesis

32. Detrital sedimentary rocks are composed predominately of:
a. silicate minerals
b. carbonate minerals
c. oxide minerals
d. sulfide and sulfate minerals
e. salts

33. A sandstone consisting of more than 25% feldspar and containing poorly sorted, angular grains is probably a(n):
a. quartz arenite
b. arkose
c. slate
d. graywacke
e. quartzite

34. Which of the following rocks is composed primarily of clay?
a. shale
b. granite
c. sandstone
d. limestone
e. dolomite

35. If you come across a very thick sandstone formation with well rounded and sorted grains that were deposited to make huge cross beds, what sort of environment does it probably represent?
a. beach
b. deep marine
c. mountain belt
d. lake, river or stream
e. dessert

36. Sedimentary rocks are important for all of the following reasons EXCEPT:
a. they contain information about the Earth's geologic history
b. they contain most of our fossil fuels, coal, oil, and natural gas
c. they contain most of our precious gems, such as diamonds and emeralds
d. they contain most of our groundwater
e. they are sometimes used as building materials

37. In the rock cycle, the process that changes igneous rock into sedimentary rock involves:
a. melting, solidification and sedimentation
b. heat and pressure induced changes
c. cooling and crystallization
d. melting, metamorphism and lithification
e. weathering, transportation and deposition

38. Which type of rock is most likely to contain fossils?
a. igneous rocks
b. metamorphic rocks
c. sedimentary rocks
d. sandstone
e. all of the above

39. Missing rock, or a surface that represents a break in the rock record caused by erosion or non-deposition.
a. unconformity
b. cross bedding
c. continental gap
d. epoch
e. epic

40. Rocks in the lowest parts of the Grand Canyon are old. How old?
a. Permian
b. Cretaceous and Tertiary
c. Cambrian
d. Precambrian
e. Phanerozoic

41. Fossils that are most useful as time indicators are called
a. index fossils
b. time fossils
c. indicator fossils
d. extinct fossils
e. correlative fossils

The next two questions refer to this table:

	parent	daughter	half life
A	C14	N14	5,730 y
B	U235	Pb207	713 my
C	K40	Ar40	1.3 by
D	U238	Pb206	4.5 by
E	Rb87	Sr87	47 by

42. Which of the parent and daughter isotopes listed above are most appropriate for determining the ages of very young rocks or geological artifacts?
a. A
b. B
c. C
d. D
e. E

43. Which of the isotopes listed in the table are radioactive?
a. all of them
b. none of them
c. only U235 and U238
d. only the daughter isotopes
e. only the parent isotopes

44. The boundary between the Precambrian and Cambrian was about
a. 6 years ago
b. 6 million years ago
c. 60 million years ago
d. 600 million years ago
e. 6 billion years ago

45. In Grand Forks County, bedrock exposed includes
a. the Navajo Sandstone
b. the Vishnu Schist
c. the Walla Walla pluton
d. the Kaibab Limestone
e. the Pierre Shale

Consider the two stratigraphic columns on the next page of this exam when you answer the following two questions

46. Which of the following formations are of Mesozoic age?
a. Mancos Shale
b. Morrison Formation
c. Navajo Sandstone
d. Chinle Formation
e. all of the above

47. If you wanted to see younger sedimentary rocks would you go to Monument Valley or to the Monticello-Bluff area?
a. Monument Valley b. Monticello-Bluff

48. What did William Smith do that was very important and made him famous?
a. he came up with the metamorphic time scale
b. he was the first person to realize that the world was older than 4000 years that is, much older than estimated by Bishop Ussher and other church scholars
c. he divided the eras into epochs
d. he mapped the geology of the Four Corners region
e. he really was responsible for discovering the principle of faunal succession.

49. Which are the smallest division of the geological time scale?
a. eons
b. periods
c. eras
d. epochs
e. members

50. A type of uncomformity in which the beds above and below are parallel.
a. angular uncomformity
b. regional uncomformity
c. noncomformity
d. serial uncomformity
e. disconformity

Short Answer Part

If you were to measure thickness of sedimentary rock layers in the central U.S. you would find that the thickness of rocks varies with age. It also varies depending on how far east or west you are.

There were times and places when very thick piles of sediments were deposited, and other times/places where little or no sediment was deposited.

In the Four Corners (Utah, Arizona, Colorado, New Mexico) region this is the record of sedimentation:

times of thick sedimentations	times of little or no sedimentation depending on where you look
	early Cambrian
late Cambrian through early Ordovician
	middle Ordovician
Late Ordovician through mid Silurian
	late Silurian through mid Devonian
Late Devonian through early Mississippian
	mid to late Mississippian
Pennsylvanian through Triassic

Another way to look at this info for the Four Corners region is on a time line:

lots of deposition	xxxxxxxx xxxxxxxxx xxxxxxxxx xxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxx xxx
no deposition	xxx xxxx xxxxxxxxx xxxxxx x x
Period	Cambrian	Ordivician	Silurian	Devonian	Mississip.	Pennsyl.	Permian	Triassic	Jurassic

The table and timeline above describe what happened in the Four Corners region. If you move east or west from there, the pattern of deposition and no-deposition is the same BUT the periods of deposition were longer. More sediments was deposited and the times of no deposition were shorter.

Questions about the above information:

1. Explain why there are some times of very thick sediment accumulation and others of little or no sediment accumulation.

2. In the center of North America, sedimentary layers are thin compared to around the edges. Why were thicker piles of sediments deposited (for longer periods of time) on the east and west edges of the continent?