Geology 101
Spring 2001
Exam #1

Multiple Guess
1. Which of the following are common cements in sedimentary rocks?
a. calcite
b. quartz
c. iron oxide
d. all three of the above
e. none of the above

2. What is the difference between conglomerate and breccia?
a. conglomerates are made of sand, breccias are made of clay
b. conglomerates are fissile, breccias are not
c. conglomerates are coarser grained than breccias
d. breccias contain angular clasts, conglomerates do not
e. breccias are finely bedded, conglomerates are coarsely bedded

3. Why do we not have a detailed time scale for the Precambrian?
a. There are not a lot of Precambrian fossils
b. There are relatively few Precambrian rocks to study
c. The Precambrian was a long time ago
d. Many Precambrian rocks have been metamorphosed or changed in some way since they formed
e. all of the above

4. When you observe an outcrop of steeply dipping inclined sedimentary layers, what principle allows you to infer that the beds were tilted after they were deposited?
a. the principle of superposition
b. the principle of separation of church and state
c. the principle of original horizontality
d. the principle of gravity
e. the principle of cross cutting relationships

5. What is the primary difference between weathering and erosion?
a. Weathering is the breaking down of rocks by mechanical means; erosion occurs by chemical means.
b. Weathering is the breaking down of minerals; erosion is the breaking down of rocks.
c. Weathering is the breaking down of rocks; erosion is the transportation of rock fragments.
d. Weathering and erosion are synonymous and may be used interchangeably.
e. They are both inorganic processes.

6. 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. very hot dry climate

7. 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

8. Which of the following transport media generally results in the most well-sorted sediments?
a. wind
b. glaciers
c. rivers
d. landslides on land
e. undersea landslides

9. 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

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

11. Which of the following statements concerning the formation of coal is NOT true?
a. the environment of deposition for coal is usually a swamp
b. coal is composed primarily of the remains of microorganisms
c. coal forms from the decomposition of organic matter in the absence of oxygen
d. because of heat and pressure, organic matter changes from peat, to lignite, to bituminous coal, and finally into anthracite
coal
e. coal deposits have formed in many places around the world

12. 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

13. Cross bedding typically forms
a. in desert sand dunes or in beach or near-shore sands
b. in sandstones that have been deposited after extensive erosion and weathering
c. in alpine areas
d. in deep ocean areas
e. in lagoons or mudflats

14. The oldest rocks found on Earth are dated at about:
a. 4.6 zillion years
b. 4.6 billion years
c. 4.6 million years
d. 4.6 trillion years
e. 570 million years

15. According to the principle of cross-cutting relationships, if a dike is found cutting across sedimentary strata, the reasonable conclusion would be that:
a. the dike is younger than the sedimentary strata
b. the dike is older than the sedimentary strata
c. the dike is of Precambrian age
d. the dike and the sedimentary strata are the same age
e. the dike may be either younger or older than the sedimentary strata

16. Quartz and clay are the two most common constituents in detrital sedimentary rocks. Why
a. Precambrian rocks are not found at the surface in most parts of the Earth
b. They are the typical end products of weathering for many rock types
c. Both are made of iron
d. Both have high solubility in water
e. all of the above

17. 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

18. Which of the following is, according to your book, "the most abundant chemical sedimentary rock?"
a. sandstone
b. evaporite
c. limestone
d. coquina
e. all of the above

19. What percentage of geological time is accounted for by the Precambrian?
a. 5%
b. 20%
c. 33%
d. 50%
e. 85%

20. The half-life of a radioactive isotope refers to:
a. one-half of the total lifespan of a parent isotope
b. the time it takes for the ratio of parent to daughter isotopes to be 1:2 (half as many parent isotopes as daughter isotopes)
c. the time it takes for the ratio of parent to daughter isotopes to be 2:1 (twice as many parent isotopes as daughter isotopes)
d. the time it takes for half of the parent isotopes to decay to daughter isotopes
e. one half the value of the decay constant

21. All of the following radiometric dating methods are useful for rocks older than 100,000 years EXCEPT:
a. uranium-lead dating
b. potassium-argon dating
c. rubidium-strontium dating
d. carbon-14 dating
e. none of the above work for rocks older than 1000,000

22. When a shell or other structure is buried in sediment, then dissolved away, to produce a fossil, we call the fossil a
a. track
b. mold
c. carbonation
d. trace fossil
e. cast

23. How does mechanical weathering add to the effectiveness of chemical weathering?
a. mechanical weathering dissolves rock and mineral matter, thus making it more susceptible to acid attack
b. mechanical weathering dissolves rock and mineral matter, thus making it more susceptible to oxidation
c. mechanical weathering dissolves rock and mineral matter, thus making it more susceptible to hydrolysis
d. mechanical weathering breaks up rocks and minerals, thus providing more surface area for chemical reaction
e. mechanical weathering breaks up rocks and minerals, thus providing more surface area for erosion

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

25. According to the normal scientific method, which is the correct order?
a. testing==>theory==>hypothesis
b. theory==>hypothesis==>testing
c. theory==>testing==>hypothesis
d. hypothesis==>theory==>testing
e. hypothesis==>testing==>theory

26. The oldest rocks in the Grand Canyon are
a. sedimentary rocks
b. named Fred
c. granites and schists
d. limestone
e. quartz

27. The difference between mudstone, sandstone and conglomerate is mostly
a. mineral composition
b. grain size
c. density
d. hardness
e. fissility

28. Why are fossils so useful for correlations?
a. there are not many fossils around
b. fossils indicate rapid compression
c. fossils are composed of carbon and other radioactive elements
d. many fossils are distinctive and only lived for short spans of geological time
e. all of the above

29. If granite and basalt are exposed at the surface in a hot wet region, which will weather faster?
a. granite
b. basalt
c. the weather at thesame rate
d. bluff answer #1
e. bluff answer #2

30. Heat speeds up chemical weathering. Why, then, does chemical weathering proceed slowly in deserts?
a. it is too hot
b. it is too cold
c. it is too dry
d. it is to wet
e. all of the above
 
Short Answer
31. In areas, such as the Grand Canyon, layers of strata are combined and given formation names. Different formations vary greatly in the kinds of rocks and minerals they contain. What is the reason for all the variation?
32. Why is quartz such a common constituent in detrital sedimentary rocks?
33. Why are shale and mudstone more widespread and common sedimentary rocks than others such as sandstone or conglomerate?
34. Suppose you find a sedimentary rock layer that is standing on end. What features might you look for to determine which side of the layer was on top at the time of deposition.
35. When you become a big time geologist and bop around the world and look at very old rocks (Precambrian) you will find that most are igneous or metamorphic, not sedimentary. Why?
36. Soils formed in humid tropical areas and the Arctic contain little organic matter. Why? Do both lack humus for the same reasons?
37. What are evaporite deposits? Name a rock which is an evaporite.
38. Briefly describe the difficulties in assigning absolute dates to layers of sedimentary rock.
39. List two conditions that favor the preservation of fossilized organisms.
40. What is lithification? Describe how it occurs and what actually happens.