Igneous Rocks Test
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Question #1
1. The process whereby ions begin to arrange themselves into orderly patterns is called
A.
a. ionization
B.
b. crystallization
C.
c. solidification
D.
d. packing
E.
e. none of the above
Question #2
2. In the early 1900’s, pioneering investigations by _______ established the sequence in which minerals crystallize from magma.
A.
a. Smith
B.
b. Playfair
C.
c. Bowen
D.
d. Lyle
E.
e. Ussher
Question #3
3. The extrusive (fine grained) equivalent of true granite is the rock
A.
a. rhyolite
B.
b. basalt
C.
c. obsidian
D.
d. tuff
E.
e. diorite
Question #4
4. Igneous rocks are classified most often by their _________ and mineral composition.
A.
a. size
B.
b. color
C.
c. texture
D.
d. shape
E.
e. formation
Question #5
5. __________ are the spherical or elongated openings seen in many aphanitic rocks left by escaping gas bubbles as magma solidifies.
A.
a. Phenocrysts
B.
b. Inclusions
C.
c. Vesicles
D.
d. Clasts
E.
e. none of the above.
Question #6
6. Which one of the following does NOT take place during the rapid cooling of magma
A.
a. ions quickly loose their motion
B.
b. small crystals form
C.
c. large numbers of crystal nuclei form
D.
d. ions readily combine
E.
e. ions migrate long distances
Question #7
7. Which of the following is a coarse-grained intrusive igneous rock similar to gray granite, but lacking visible quartz crystals?
A.
a. basalt
B.
b. andesite
C.
c. peridotite
D.
d. obsidian
E.
e. diorite
Question #8
8. According to Bowen’s reaction series, the first ferromagnesian mineral to crystallize from a typical magma is:
A.
a. quartz
B.
b. olivine
C.
c. pyroxene
D.
d. orthoclase
E.
e. biotite mica
Question #9
9. As magma migrates upward it may incorporate some of the surrounding country rock in a process called:
A.
a. mixing
B.
b. differentiation
C.
c. assimilation
D.
d. acquiring
E.
e. none of the above
Question #10
10. Which one of the following does NOT refer to the texture of an igneous rock?
A.
a. glassy
B.
b. porphyritic
C.
c. clastic
D.
d. aphanitic
E.
e. phaneritic
Question #11
11. Igneous rocks which have potassium feldspar and quartz as their primary components are said to have a(n) ________ composition.
A.
a. granitic
B.
b. mafic
C.
c. basaltic
D.
d. clastic
E.
e. porphyritic
Question #12
12. The process of developing more than one rock type from a common magma is called magmatic
A.
a. isolation
B.
b. segregation
C.
c. streak
D.
d. differentiation
E.
e. compounding
Question #13
13. Rocks composed almost entirely of ferromagnesian minerals are often referred to as
A.
a. felsic
B.
b. clastic
C.
c. ultramafic
D.
d. glassy
E.
e. granitic
Question #14
14. The most important factor affecting the texture of an igneous rock is the _______ of the magma.
A.
a. location
B.
b. starting temperature
C.
c. composition
D.
d. rate of cooling
E.
e. final temperature
Question #15
15. A rock which has large crystals embedded in a matrix of smaller crystals is said to have a(n) _______ texture.
A.
a. aphanitic
B.
b. fragmental
C.
c. glassy
D.
d. phaneritic
E.
e. none of these.
Question #16
16. The slow cooling of magma results in the formation of rather __________ mineral crystals.
A.
a. large
B.
b. irregular
C.
c. small
D.
d. colorless
E.
e. odd-shaped
Question #17
17. The intrusive equivalent of basalt is _____________.
A.
a. granite
B.
b. gabbro
C.
c. diorite
D.
d. andesite
E.
e. obsidian
Question #18
18. Igneous rocks that form at the surface or as small masses within the upper crust possess a very fine-grained texture called
A.
a. porphyritic
B.
b. aphanitic
C.
c. conchoidal
D.
d. phaneritic
E.
e. fragmental
Question #19
19. The left branch of Bowen’s reaction series is called a(n) _____ reaction series because each mineral has a different crystalline structure.
A.
a. discontinuous
B.
b. intermediate
C.
c. continuous
D.
d. changing
E.
e. alternate
Question #20
20. The best-known and most important ore deposits are those that are produced from ________ solutions.
A.
a. brine
B.
b. hydrothermal
C.
c. potassium
D.
d. carbonate
E.
e. secondary
Question #21
21. Which one of the following terms is used by geologists to denote any rock with a high percentage of ferromagnesian minerals?
A.
a. calcic
B.
b. mafic
C.
c. ferric
D.
d. felsic
E.
e. masic
Question #22
22. Rocks that consist of unordered atoms are referred to as
A.
a. coarse grained
B.
b. fragmental
C.
c. volatile
D.
d. glass
E.
e. none of the above
Question #23
23. The igneous rock ________ is composed of about 25 to 35 percent quartz and over 50 percent potassium feldspar and sodium-rich feldspar.
A.
a. basalt
B.
b. peridotite
C.
c. granite
D.
d. obsidian
E.
e. none of the above.
Question #24
24. Igneous rocks of this composition crystallize at very high temperatures.
A.
a. Granitic (felsic)
B.
b. Andesitic (intermediate)
C.
c. Basaltic (mafic)
D.
d. Ultramafic
Question #25
25. Rocks of this type contain mostly the minerals quartz and feldspar
A.
a. Granitic (felsic)
B.
b. Andesitic (intermediate)
C.
c. Basaltic (mafic)
D.
d. Ultramafic
Question #26
26. Rocks of this composition contain pyroxene and calcium-rich plagioclase feldspar.
A.
a. Granitic (felsic)
B.
b. Andesitic (intermediate)
C.
c. Basaltic (mafic)
D.
d. Ultramafic
Question #27
27. Rocks of this type crystallize at the lowest (coolest) temperatures.
A.
a. Granitic (felsic)
B.
b. Andesitic (intermediate)
C.
c. Basaltic (mafic)
D.
d. Ultramafic
Question #28
28. Which of the following is the rock type with phaneritic texture and andesitic composition?
A.
a. Granite
B.
b. Diorite
C.
c. Rhyolite
D.
d. Andesite
E.
e. Basalt
Question #29
29. Which of the following rock types is a dark rock with phaneritic texture?
A.
a. Peridotite
B.
b. Diorite
C.
c. Rhyolite
D.
d. Andesite
E.
e. Basalt
Question #30
30. Which factors help produce the texture of igneous rocks?
A.
a. the amount of dissolved gases in magma
B.
b. the rate at which magma cools
C.
c. the amount of silica present
D.
d. all of the above
E.
e. only b and c
Select the letter that labels the correct part of the image.
Question #31
31. The magma here is probably most silica-rich.
A.
A
B.
B
C.
C
Question #32
32. The magma here is probably most rich in iron and magnesium.
A.
A
B.
B
C.
C
Question #33
33. The magma here is intermediate in composition
A.
A
B.
B
C.
C
Question #34
34. biotite mica
A.
A
B.
B
C.
C
D.
D
Question #35
35. quartz
A.
A
B.
B
C.
C
D.
D
Question #36
36. potassium feldspar
A.
A
B.
B
C.
C
D.
D
Question #37
37. plagioclase feldspar
A.
A
B.
B
C.
C
D.
D
Question #38
38. plagioclase feldspar
A.
A
B.
B
Question #39
39. pyroxene
A.
A
B.
B
Question #40
40. The picture to the right represents a type of rock formed from a fine-grained volcanic ash flow with a frothy, glassy texture. Which is the rock type?
A.
a. porphyry
B.
b. obsidian
C.
c. pumice
D.
d. komatiite
E.
e. peridotite