Geology Cafe

Introduction to Geology

Quiz 7 - Igneous Rocks, Volcanoes, and Volcanic Activity
1. The geothermal gradient is:
a. the change in temperature that increases with depth.
b. averages 20 to 30 degrees C per kilometer in the upper crust.
c. can vary significantly from one location to another.
d. all of the above.

2. What process (or processes) can generate magma?
a. decreases in pressure (such as caused by an earthquake)
b. introduction of volatiles (water, gases) under high pressure
c. increased rate of heat flow
d. all of the above

3. Which factors help produce the texture of igneous rocks?
a. the amount of dissolved gasses in magma.
b. the amount of silica present.
c. the rate at which magma cools.
d. all of the above.

4. Igneous rocks are classified based on:
a. number of elements.
b. chemical composition.
c. texture.
d. a and b only.
e. b and c only.

5. Which of these rock types contain the most quartz?
a. granite
b. andesite
c. gabbro
d. basalt
e. pyroxenite

6. Which of these rock types has a fine-grained texture?
a. diorite
b. granite
c. peridotite
d. gabbro
e. basalt

7. Which of these is an ultramafic rock?
a. diorite
b. rhyolite
c. gabbro
d. peridotite
e. andesite

8. According to Bowen's reaction series, which of the following minerals has the highest crystallization temperature?
a. biotite
b. quartz
c. olivine
d. potassium feldspar
e. pyroxene

9. Most of the upper mantle is made up of:
a. gabbro and basalt
b. andesite and diorite
c. peridotite and pyroxenite
d. a'a and pahoehoe
e. granite and rhyolite

10. Devils Tower, Wyoming (used in the movies Close Encounters of a Third Kind and Paul) is an example of a:
a. sill
b. stock
c. dike
d. palisade
e. cinder cone

Extra Credit
: The hottest lava observed on the Earth surface are associated with:
a. supervolcanoes (continental hotspots), like Yellowstone.
b. composite volcanoes, like Mount St. Helens in the Cascades volcanic arc.
c. oceanic hotspots, like Kilauea volcano on Hawaii.
d. island arc volcanoes, like Mount Pelee on the Caribbean island of Martinique.
e. continental rift zones, like the East African Rift volcanoes like Erta Ale, Ethiopia.