Geology 101
Exam #2
Fall 2002


1. Why do magmas rise to the surface?
a. Coriolis force
b. they are aphanitic
c. magma is not as dense as solid rock
d. magma is denser than solid rock
e. as ash settles it pushes down on a caldera

2. A porphyritic rock is one
a. in which mineral grains are generally small
b. in which mineral grains are generally large
c. that contains large phenocrysts in a matrix
d. that forms from settled ash
e. that contains abundant glass such as obsidian

3. Which of these is/are associated with a subduction zone?
a. Columbia River flood basalts
b. Mt. Rushmore
c. Sierra Nevada batholith
d. Hawaiian islands
e. volcanic island arcs

4. Maurice and Katya Kraft
a. were killed by a volcano
b. invented the reflecting goniometer
c. are the names of the (hypothetical) first minerals every discovered
d. were the first people to figure out that continents drift
e. are responsible for coming up with the system for dividing minerals into classes

5. Ions are
a. atoms that are bonded to other atoms
b. atoms formed of the common elements
c. atoms that have an electrical charge because the lost or gained an electron
d. the same thing as compounds
e. atoms that are very soluble in water because they are large and easily dissolved

6. 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.

7. 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

8. Which of the following is a passive continental margin?
a. west coast of Europe
b. west coast of South America
c. west coast of the United States
d. east coast of Japan
e. all of the above

9. In general, gems are
a. rare minerals
b. radioactive minerals
c. beautiful varieties of common minerals
d. not colored or dyed or altered in any way from the way they occur naturally
e. made of diamond

10. What information is key to identifying the locations of lithospheric plate boundaries?
a. location of earth quakes
b. location of granites
c. location of passive margins
d. variations in igneous rock types
e. all of the above

11. Calcite and halite are two of the most common minerals that precipitate from water. Why?
a. the elements that make up the two minerals are very common
b. the elements that make up the two minerals are very soluble
c. only a small change in conditions can cause these minerals to precipitate
d. ocean waters are rich in the elements that make up these two minerals
e. all of the above

12. All minerals must, by definition, be crystalline. This means that
a. they have geometric shapes with flat crystal faces
b. they have a fixed chemical composition
c. they have unique physical properties that help identify them
d. their atoms occur in a specific, repeating, pattern
e. all of the above

13. What are the three basic types of plate boundaries
a. subduction, reduction, deduction
b. rifts, seams, valleys
c. mid ocean ridges, spreading centers, subduction zones
d. volcanic arcs, transform faults, subduction zones
e. divergent, convergent, transform fault

14. The primary difference between magma and lava is:
a. one occurs at divergent plate boundaries, the other at convergent plate boundaries
b. they are produced from different parent materials
c. magma becomes lava anytime it is in a cooling condition
d. one is below the ground, the other is above ground
e. there is no difference, they are different words for the same thing

15. The reason over 50 people died when Mt. St. Helens erupted is because
a. the eruption took place on Monday
b. the eruption was a fissure eruption
c. the eruption was a complete surprise
d. the basalt flowed over the ground at high speed
e. people didn't believe the warnings and were too close

16. When we use a number to describe a mineral's hardness, we are using the _________________.
a. Mohs scale
b. Richter scale
c. Peterson tenacity test
d. Abrasion scale
e. cleavage number

17. Which of the following is/are involved in the formation of new crust at mid ocean ridges?
a. hot asthenosphere rises
b. magma reaches the surface
c. pillow basalts may form
d. crust moves away from ridges
e. all of the above

18. What is a Wadati-Benioff zone?
a. anywhere there is a passive continental margin
b. a place where passive continental margins meet spreading centers
c. the location of an active mid ocean ridge or other spreading center
d. earthquake zone associated with a subduction zone
e. a place such as California where a major transform fault occurs

19. Bowen's reaction series shows:
a. which minerals crystallize first as a magma cools from a liquid to a solid
b. which rocks will develop an aphanitic texture and which will form a phaneritic texture
c. why quartz, potassium feldspars, and muscovite form as mafic minerals, while olivine and pyroxene form as felsic minerals
d. which magmas will form extrusive igneous rocks and which will form intrusive igneous rocks
e. which minerals crystallize first as a magma changes from a solid to a liquid

20. Salt crystals are considered to be minerals, but sugar crystals are not. Why?
a. salt is inorganic but sugar is organic
b. salt is organic but sugar is inorganic
c. salt is soluble in water and sugar is not
d. sugar is soluble in water and salt is not
e. sugar is very soft.

21. The force that causes pyroclastic volcanoes to explode violently is
a. pressure from volcanic gases
b. density differences within the magma that force part of the magma upward
c. the Vikings are the crummiest football team I have ever seen
d. hot convection currents in the asthenosphere that pushes magma upward
e. gravity

22. What is the prime characteristic that mineralogists use to put minerals into classes?
a. hardness
b. how the minerals formed
c. color
d. size of mineral grains
e. chemistry

23. Two minerals that have identical composition but different atomic arrangements are called _________.
a. halides
b. silicates
c. kimberlites
d. facets
e. polymorphs

24. All silicate mineral have what in common?
a. they all form from magmas
b. they all contain silicon-oxygen tetrahedra
c. they all contain iron and magnesium
d. they all contain silicic acid
e. they all break down quickly at the Earth's surface

25. Which of the following is NOT a mineral?
a. quartz
b. copper
c. granite
d. calcite
e. plagioclase (feldspar)

26. If new crust is being created at mid ocean ridges, we might think that means that the Earth is getting larger. But, it isn't. Why doesn't the Earth get larger?
a. transform faults take up some of the "slack"
b. island arcs are also sites of new crustal formation
c. continents drift apart making more room for the new crust
d. old crust is subducted in subduction zones
e. all of the above

27. A rock made of shell fragments is a ____________ rock.
a. clastic sedimentary
b. chemical sedimentary
c. igneous
d. metamorphic
e. lithic

28. An extrusive igneous rock composed primarily of plagioclase and perhaps some olivine, pyroxene or amphibole is called
a. sandstone
b. granite
c. komatiite
d. basalt
e. pyroclastic

29. Which of the following are important factors that determine the type of soil that may form in an area?
a. substrate
b. climate
c. slope steepness
d. vegetation type
e. all of the above

30. When a rock is attacked by water, wind, gravity or some other force and breaks up into smaller pieces, this is an example of _________ weathering.
a. chemical
b. solutional
c. biological
d. mechanical
e. proportional

31. What is the largest of all intrusive igneous bodies?
a. dike
b. sill
c. loppolith
d. pluton
e. batholith

32. Which one of the following rocks probably underwent the fastest cooling rate?
a. granite
b. gabbro
c. basalt
d. obsidian
e. all of the above 33. An intrusive (plutonic) K-feldspar, quartz and perhaps some plagioclase, amphibole or biotite is called
a. sandstone
b. granite
c. komatiite
d. basalt
e. pyroclastic

34. "A coherent, naturally occurring solid, consisting of an aggregate of minerals or a mass of glass."
a. crystal
b. rock
c. formation
d. unit
e. any of the above

35. Which type of rock typically shows foliation?
a. plutonic (intrusive) igneous
b. volcanic (extrusive) igneous
c. conglomerate
d. metamorphic
e. heavy metal

Short/Medium Answer Questions

1. Andalusite and Sillimanite are two different minerals (that you probably have never heard of) that have exactly the same composition. That means they are polymorphs. How can this be? What I am asking is this: how can two distinctly different minerals have the same composition? (Although it is not particularly relevant to this question, the formula for the two is Al2SiO5.)

2. Some crystals develop nice smooth crystal faces, so they reflect light well and sparkle. Most crystals do not. They may just be blobby shapes with no smooth faces. Explain this.

3 When you melt ice, you get water. When you melt wax, you get liquid wax. Clearly, in these two cases, what you get depends on what you melt. the crust and mantle of the Earth are not exactly the same composition, and magmas come from both. So, we might expect that we would get two types of magmas. But, we see much more variety than that, even though the various parts of the Earth are relatively uniform in composition. So, why do we see magmas of many different compositions at the Earth's surface? Explain this