1. Chapter 4

2. 1. Which of the following features would indicate an igneous rock cooled quickly?
large mineral crystals
small mineral crystals
dark-colored minerals
light-colored minerals

3. 2. What distinguishes a felsic extrusive rock (rhyolite) from a felsic intrusive igneous rock (granite)?
mineral composition
crystal size
both of these

4. 3. Where is the most likely location for molten rock to cool and minerals to form quickly?
in Earth’s crust
at Earth’s surface
in Earth’s core
in Earth’s mantle

5. 4. The presence of large amounts of igneous rocks composed of small mineral crystals is suggestive of what process occurring in the past?
volcanic eruptions
earthquakes
floods
landslides

6. 5. What kind of cooling history do porphyritic textures indicate?
slow
fast
instantaneous
slow then fast
fast then slow

7. 6. Silica is abundant in most igneous rocks, meaning that the elements
6. Silica is abundant in most igneous rocks, meaning that the elements and make up a large percentage of their weight.
iron and magnesium
sodium and potassium
silicon and oxygen
calcium and aluminum

8. 7. The primary difference between felsic and mafic igneous rocks is:
crystal size.
mineral composition.
cooling rate.
depth of formation.

9. 8. Felsic igneous rocks contain more. and are
8. Felsic igneous rocks contain more and are in color compared to mafic igneous rocks.
iron; darker
iron; lighter
silica; darker
silica; lighter

10. 9. Rocks of which composition will melt at the lowest temperature?
mafic
intermediate
felsic
All of these will melt at the same temperature.

11. 10. Rocks of which composition will melt at the highest temperature?
mafic
intermediate
felsic
All of these will melt at the same temperature.

12. 11. Which mineral will crystallize at the highest temperature?
quartz
muscovite
olivine
pyroxene
All of these will crystallize at the same temperature.

13. 12. Which mineral will crystallize at the lowest temperature?
quartz
muscovite
olivine
pyroxene
All of these will crystallize at the same temperature.

14. 13. Partial melting will cause minerals with a relatively
13. Partial melting will cause minerals with a relatively melting point to become a liquid.
lower
higher

15. 14. Increased pressure will the melting temperature of a rock.
decrease
not change

16. 15. The addition of water will the melting temperature of a rock.
increase
decrease
not change

17. 16. The body of igneous rock shown is composed of large mineral crystals and formed .
slowly below the surface
quickly below the surface
slowly at the
surface
D. quickly at the

18. 17. What type of igneous intrusion is shown?
dike
sill
pluton

19. 18. Which tectonic setting is most likely to have intermediate plutons?
hot spot
spreading center
subduction zone

20. 19. What is a major process of magma production at spreading centers?
partial melting
decompression melting
fluid-induced melting

21. 20. What is a major process of magma production at subduction zones?
partial melting
decompression melting
fluid-induced melting