Exam 2: Geology 101, Fall 2005 – The “Rock” test

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1. The texture of a rock gives clues as to how it formed. For example, igneous rocks are composed of minerals that are interlocked. If the minerals are small (i.e., cannot be seen with the unaided eye), the rock most likely formed (a)_____ and the rock has (b)_____ texture.

A. (a) deep in the earth, (b) aphanitic

B. (a) at or near the earth's surface, (b) aphanitic

C. (a) from a slow cooling magma, (b) aphanitic

D. (a) underwater, (b) phaneritic

E. none of the above combinations

2. A/an (a)_____ rock, one that formed at or near the earth's surface, can also be called a/an (b)_____ rock, based on how it formed, or a/an (c)_____ rock, based on what the rock looks like.

A. (a) extrusive, (b) volcanic, (c) aphanitic

B. (a) intrusive, (b) volcanic, (c) aphanitic

C. (a) extrusive, (b) plutonic, (c) aphanitic

D. (a) extrusive, (b) volcanic, (c) phaneritic

E. none of the above combinations

3. Magma is defined as molten rock, and lava is defined as:

A. crystallized rock

B. underground magma

C. magma at the surface

D. a magma high in Si and low in Fe and Mg

E. none of the above

4. Why is the color of the rock important in classifying extrusive igneous rocks in hand samples?

A. the color tells the texture

B. the minerals are too small to see and dark color indicates the presence of Fe-rich minerals

C. color gives clues on how the rock formed (e.g., dark rocks form at the earth's surface)

D. color is of no help in classifying extrusive igneous rocks

E. none of the above

5. Which of the following minerals contain iron?

A. quartz

B. feldspars

C. pyroxenes

D. halite

E. all of the above

6. The main extrusive igneous rock types rhyolite, andesite, and basalt form from magmas of different compositions referred to as _____, respectively.

A. dark, grayish, light

B. mafic, intermediate, mafic

C. felsic, intermediate, mafic

D. low in Si, low in Fe, high in Si

E. none of the above

7. Basalt is the most abundant extrusive igneous rock and is (a)_____-colored, while granite is the most abundant intrusive igneous rock and is (b)_____-colored. Basalt forms when a/an (c)_____ magma cools rapidly at the surface, while granite forms when a/an (d)_____ magma cools slowly at depth.

A. (a) light, (b) dark, (c) mafic, (d) felsic

B. (a) dark, (b) dark, (c) felsic, (d) mafic

C. (a) light, (b) dark, (c) mafic, (d) intermediate

D. (a) dark, (b) light, (c) mafic, (d) felsic

E. none of the above combinations

8. Granite is the intrusive equivalent (i.e., composed of the same magma type) of:

A. gabbro

B. andesite

C. basalt

D. sandstone

E. none of the above

9. Magma viscosity varies for the different magma types, and viscosity is controlled by the chemistry of the magma. (a)_____ magma is the most viscous magma and has the highest (b)_____ content, which causes formation of minerals with a greater polymerization of the silicate tetrahedral.

A. (a) Mafic, (b) Fe

B. (a) Mafic, (b) Si

C. (a) Felsic, (b) Si

D. (a) Felsic, (b) Fe

E. none of the above combinations

10. A composite volcano, which is composed of andesite, has steeper slopes than a shield volcano, which is composed of basalt, because:

A. the composite volcano forms faster

B. the composite volcano forms slower

C. the lava in the composite volcano is more viscous

D. the lava in the composite volcano is less viscous

E. none of the above

11. The term "composite volcano" was derived from the fact that:

A. the rock that forms the volcano is composed of different minerals

B. the volcano is composed of smaller volcanoes

C. the lava that erupts to form the volcano is composed of a mixture of felsic and mafic magmas

D. the volcano is composed of many lava flows

E. none of the above

12. Rocks can melt by (a)____ or (b)_____.

A. (a) increasing temperature, (b) increasing pressure

B. (a) decreasing temperature, (b) change in chemistry

C. (a) increasing temperature, (b) decreasing pressure

D. (a) decreasing temperature, (b) increasing pressure

E. none of the above combinations

13. Bowen's reaction series explains:

A. how we classify igneous rocks

B. how igneous rocks form

C. the order in which minerals crystallize in a cooling magma

D. why volcanoes erupt

E. none of the above

14. If a magma body starts cooling at depth, (a)_____ and (b)____-feldspar would be the first minerals to form, and they would combine to form the rock type (c) _____.

A. (a) olivine, (b) Ca, (c) basalt

B. (a) olivine, (b) Ca, (c) gabbro

C. (a) pyroxene, (b) Ca, (c) basalt

D. (a) quartz, (b) K, (c) granite

E. none of the above combinations

15. Which of the following are processes that can change magma composition?

A. crystal settling

B. assimilation

C. partial melting

D. magma mixing

E. all of the above

16. Crystal size relates to cooling rate, and several rock types clearly show this. For example, (a)_____ is a type of (b)_____ igneous rock with (c)_____ crystals.

A. (a) pegmatite, (b) intrusive, (c) very large

B. (a) granite, (b) intrusive, (c) large

C. (a) obsidian, (b) extrusive, (c) very small

D. all of the above

E. none of the above combinations

17. Some extrusive igneous rock types occur along certain plate margins. For instance, (a)_____ occurs where two ocean plates pull apart, and (b)_____ forms where an ocean plate collides with a continental plate.

A. (a) basalt, (b) andesite

B. (a) rhyolite, (b) granite

C. (a) diorite, (b) andesite

D. (a) andesite, (b) basalt

E. none of the above combinations

18. The guest lecturer (from four weeks ago) talked about his research dealing with:

A. groundwater

B. fossils

C. minerals

D. volcanoes

E. petroleum

19. Which of the following were part of the sediment–sedimentary rock cycle that I presented?

A. weathering

B. erosion and transportation

C. deposition

D. lithification and crystallization

E. All of the above are part of the sediment–sedimentary rock cycle.

20. The process that turns rocks into sediment is called:

A. weathering

B. erosion

C. deposition

D. lithification

E. none of the above

21. In class I discussed two kinds of weathering. (a)_____ weathering deals with rocks breaking apart by applied forces (i.e., the rock breaks), while (b)_____ weathering deals with minerals in the rocks dissolving.

A. (a) Heat, (b) salt

B. (a) Environmental, (b) chemical

C. (a) Mechanical, (b) chemical

D. (a) Mechanical, (b) environmental

E. none of the above combinations

22. Chemical weathering can be used to explain elements found in the groundwater under Moscow. For instance, the high (a)_____ level is the result of weathering of mafic minerals, and the high Ca content is the result of weathering of (b)_____.

A. (a) Fe, (b) feldspars

B. (a) Si, (b) quartz

C. (a) Mg, (b) quartz

D. (a) Fe, (b) quartz

E. none of the above

23. When Ca from groundwater reaches the air (like in your kitchen sink), it combines with oxygen and carbon dioxide to form:

A. quartz

B. rust

C. calcite

D. scum

E. none of the above

24. Soils are formed from the chemical weathering of rocks and the leaching of elements, usually accompanied by the addition of water from the atmosphere. For instance, K-feldspar (KAlSi₃O₈) weathers to form a clay mineral with the chemical formula:

A. Mg₃Si₂O₅(OH)₄

B. Al₂Si₂O₅(OH)₄

C. Fe₃Si₂O₅(OH)₄

D. Ca₃Si₂O₅(OH)₄

E. none of the above

25. Once sediments are formed, they are removed by the processes of (a)_____ and moved by the process of (b)_____

A. (a) erosion, (b) transportation

B. (a) weathering, (b) lithification

C. (a) erosion, (b) weathering

D. (a) weathering, (b) erosion

E. none of the above combinations

26. A well-rounded, well-sorted sediment could be transported a (a)_____ distance by (b)_____.

A. (a) short, (b) wind

B. (a) long, (b) ice

C. (a) long, (b) water

D. (a) short, (b) water

E. none of the above combinations

27. Sedimentary structures help a geologist determine the conditions in which a sediment was deposited. For instance, (a)_____ might form in flowing water, while (b)____ might form in standing water.

A. (a) cross-bedding, (b) graded-bedding

B. (a) ripple marks, (b) cross-bedding

C. (a) horizontal bedding, (b) sand dunes

D. (a) mud cracks, (b) cross-bedding

E. none of the above combinations

28. Sedimentary rocks are classified based upon:

A. where and how they form

B. their composition and texture

C. what they are made of

D. grain size

E. none of the above combinations

29. The texture classification for clastic sedimentary rocks is based on grain sizes. From smallest to largest, the grain size names are:

A. mud, sand, gravel

B. sand, gravel, boulders

C. mud, sand, boulders

D. clay, sand, boulders

E. none of the above

30. Both conglomerates and breccias are composed of (a)_____, but a breccia is located (b)_____ to/from its source of sediment.

A. (a) boulders, (b) closer

B. (a) gravel, (b) closer

C. (a) gravel, (b) farther

D. (a) boulders, (b) farther

E. none of the above combinations

31. What is the quickest way to tell the difference between silt- and clay sized-particles in a rock?

A. use a microscope

B. ask a geologist

C. chew on the rock

D. determine how the rock formed

E. none of the above

32. The most common mineral found in sandstone is (a)_____, which is very resistant to chemical weathering, while (b)_____ is the most common mineral in a limestone.

A. (a) feldspar, (b) calcite

B. (a) quartz, (b) calcite

C. (a) quartz, (b) dolomite

D. (a) feldspar, (b) carbonate

E. none of the above combinations

33. Coal is a sedimentary rock that formed from:

A. very small fossils composed of quartz

B. very small fossils composed of calcite

C. very small fossils composed of organic material

D. large masses of organic material

E. none of the above

34. Metamorphic rocks form from _____ by increases in temperature and pressure.

A. melting of igneous rocks

B. weathering of igneous rocks

C. alteration of existing rocks in the solid state

D. melting of sedimentary rocks

E. none of the above

35. Increases in temperature result from (a)_____, and increases in pressure result from (b)_____.

A. (a) rocks being buried, (b) rocks being buried

B. (a) plate motion, (b) lithification of sediments

C. (a) plate motion, (b) foliation of rocks

D. (a) foliation of rocks, (b) plate motion

E. none of the above combinations

36. Confining pressure (a)_____, while directed stress (b)_____.

A. (a) changes the shape of an object, (b) changes the size of the object

B. (a) changes the size of an object, (b) changes the shape of an object

C. (a) is a type of non-directed stress, (b) changes the size of the object

D. (a) commonly occurs in metamorphic rocks, (b) never occurs in metamorphic rocks

E. none of the above combinations

37. Different plate boundaries have different pressure-temperature gradients. For instance, a/an (a)_____ plate boundary would have a higher temperature gradient, while a/an (b)_____ plate boundary would have a higher pressure gradient.

A. (a) diverging, (b) converging

B. (a) non-active, (b) active

C. (a) converging, (b) diverging

D. (a) active, (b) non-active

E. none of the above combinations

38. A/an _____ is best defined as “a material with specific chemical and physical properties.”

A. element

B. mineral

C. rock

D. phase

E. none of the above

39. In question 24, I pointed out how a feldspar would weather to a clay (by the loss of certain elements and the addition of water). In the process of metamorphism, clays alter to form other minerals, often with the loss of water. Which mineral below might form from a clay mineral with the formula Al₂Si₂O₅(OH)₄ during metamorphism?

A. Al₂SiO₅

B. Mg₃SiO₅

C. Fe₃SiO₅

D. Ca₃SiO₅

E. none of the above

40. Metamorphic rocks are classified based upon:

A. where and how they form

B. their composition and texture

C. what they are made of

D. grain size

E. none of the above combinations

41. There are two basic textures for metamorphic rocks. (a)_____ rocks form from directed stresses, while (b)_____ rocks form from rocks which only contain one mineral.

A. (a) Foliated, (b) non-foliated

B. (a) Non-foliated, (b) foliated

C. (a) Schist, (b) slate

D. (a) Marble, (b) phyllite

E. none of the above combinations

42. When a shale undergoes directed-stress metamorphism, which of the following rock sequences would it form over time?

A. slate, phyllite, schist, gneiss

B. gneiss, schist, phyllite, slate

C. marble, quartzite

D. marble

E. none of the above

43. The foliation direction in a schist is _____ to the main stress direction.

A. parallel

B. perpendicular

C. Schist is not foliated.

D. Foliation direction and stress direction are not related.

E. none of the above

44. Geologists use (a)_____ to determine “what event came first,” and they use (b)_____ to determine the number of years since some event occurred.

A. (a) relative time, (b) absolute time

B. (a) absolute time, (b) relative time

C. (a) radioactive dating, (b) cross-cutting relationships

D. (a) tree rings, (b) varves

E. none of the above

45. Which is the correct series of geologic eras, from oldest to youngest?

A. paleozoic, mesozoic, cenozoic

B. cenozoic, paleozoic, mesozoic

C. mesozoic, cenozoic, paleozoic

D. mesozoic, paleozoic, cenozoic

E. none of the above

46. The law of superposition states that:

A. younger sediments overlie older sediments

B. older sediments overlie younger sediments

C. old rocks are on top of young rocks

D. both B and C

E. none of the above

47. The law of cross-cutting relationships states that:

A. new material cuts old

B. old material cuts new

C. sediments are deposited horizontally

D. sediments are deposited vertically

E. none of the above

48. Radioactive dating is the main method geologists use to determine the age of rocks. In this method geologists use the fact that a/an (a)____ element decays to form its (b)_____ and by knowing the decay rate ages can be determined.

A. (a) parent, (b) daughter

B. (a) daughter, (b) parent

C. (a) radioactive, (b) parent

D. both A and C

E. none of the above combinations

49. The half-life of U238 decaying to Pb206 is 4.5 billion years. What would be the ratio of U238 to Pb206 in a rock that formed at the same time the earth formed?

A. 4 to 1

B. 3 to 1

C. 2 to 1

D. 1 to 1

E. none of the above

50. I have made sure that my ID and name are correctly entered on the scan sheet, I will take the test with me when I leave, and I have answered all the questions on the test and entered them on the scan sheet.

A. yes

B. no