Question 1

Mafic rocks have silica contents of __________and are mainly composed of_________ .

Accepted Answer

A)   around 50%, pyroxene and plagioclase feldspar
B)   up to 70% quartz and feldspar
C)   under 40%, olivine and pyroxene
D)   more than 85%, potassium rich feldspars and micasE) B) and C)
F) A) and C)

Question 2

Which texture would be most unlikely to occur in an extrusive igneous rock?

Accepted Answer

A)   glassy
B)   pyroclastic
C)   aphanitic
D)   phaneriticE) A) and B)
F) A) and C)

Question 3

Which statement best describes the crystallization of magmas?

Accepted Answer

A)   During crystallization, which can occur over an interval of about 200° C, the composition of the residual melt continuously changes as particular ions are selectively removed and incorporated into certain minerals that crystallize early at high temperature.
B)   A felsic magma produces only one rock type equal to the melt composition by crystallizing quartz, feldspar, and ferromagnesian minerals in fixed proportions and compositions until all of the melt is used up.
C)   Like the freezing of water, cooling magmas hit their crystallization temperature and stop cooling until all the melt has crystallized, whereupon cooling resumes.
D)   Early formed crystals are big and irregular in shape, but gradually get smaller and have better developed faces with time as they react with the residual melt.E) None of the above
F) C) and D)

Question 4

Which of the following best describes an aphanitic texture?

Accepted Answer

A)   The rock consists of broken, volcanic- rock and mineral fragments.
B)   The rock is crystalline; mineral grains are of distinctly different sizes.
C)   The rock is crystalline; mineral grains are too small to be visible without a magnifying lens or microscope.
D)   The mineral grains have glassy textures.E) C) and D)
F) All of the above

Question 5

Felsic rocks like granite_______ .

Accepted Answer

A)   make up most of the ocean floor and volcanic island chains
B)   are major constituents of the continental crust
C)   are extremely rare on Earth but abundant on the Moon
D)   form mainly in volcanic island chainsE) B) and C)
F) A) and C)

Question 6

Explosive volcanic eruptions occur___________ .

Accepted Answer

A)   when crystallization forces exceed the strength of the volcano
B)   when violently escaping gases evolve suddenly to drop the magma density and propel molten magma from the chamber
C)   in response to deflation of the volcano
D)   whenever basaltic magma extrudes on the seafloorE) A) and B)
F) B) and D)

Question 7

Felsic rocks have silica contents of______ are rich in______ .

Accepted Answer

A)   around 50%, pyroxene and plagioclase feldspar
B)   more than 85%, calcium rich feldspars and amphiboles
C)   about 70%, quartz and feldspar
D)   under 40%, olivine and pyroxeneE) B) and C)
F) All of the above

Question 8

Pyroxene, hornblende, and biotite are all minerals found on the ___________series of Bowen's Reaction Series.

Accepted Answer

The answer of Pyroxene, hornblende, and biotite are all minerals...

Question 9

What would you name a light pink, aphanitic, fragmental pyroclastic with sparse quartz phenocrysts?

Accepted Answer

A)   andesite breccia
B)   quartz porphyry
C)   rhyolite tuff
D)   porphyritic graniteE) All of the above
F) B) and C)

Question 10

What is the most common extrusive rock type for any volcanic environment on the Earth or even on the Moon?

Accepted Answer

A)   rhyolite
B)   obsidian
C)   andesite
D)   basaltE) A) and B)
F) A) and C)

Question 11

What small, intrusive igneous rock bodies often contain gem- quality crystals of minerals such as beryl and tourmaline and high concentrations of relatively rare elements such as lithium, cesium, and uranium?

Accepted Answer

A)   welded tuff sheets
B)   granitic pegmatites
C)   diorite plutons
D)   basaltic lavasE) B) and C)
F) All of the above

Question 12

Which of the following minerals crystallize early in Bowen's reaction series?

Accepted Answer

A)   quartz
B)   biotite
C)   muscovite
D)   olivineE) All of the above
F) A) and B)

Question 13

What kind of coarse grained plutonic rock would you expect to find in the ocean crust underneath an undersea basaltic volcano?

Accepted Answer

A)   gabbro
B)   peridotite
C)   diorite
D)   graniteE) A) and C)
F) None of the above

Question 14

As melts cool their viscosity increases (they lose their mobility and get stiffer)  even before they start to crystallize because_________ .

Accepted Answer

A)   their ions become more disordered
B)   the silica tetrahedra in the melt start to link up and make larger and stronger units
C)   they increase in volume
D)   all of the sodium and potassium escapeE) All of the above
F) B) and D)

Question 15

The main factors which directly govern the development of texture in all igneous rocks are________

Accepted Answer

A)   cooling rate, dissolved volatiles, and silica content
B)   weathering and climate
C)   buoyancy, crystal settling, and partial melting
D)   volcano or pluton size and shapeE) A) and C)
F) None of the above

Question 16

What two rock types are often found interlayered in the same volcanic deposit?

Accepted Answer

A)   obsidian and pumice
B)   andesite and komatiite
C)   granite and gabbro
D)   peridotite and basaltE) A) and C)
F) B) and D)

Question 17

The most common non- ferromagnesian silicate minerals (>40 %)  in most igneous rocks are_________

Accepted Answer

A)   olivine
B)   feldspar
C)   quartz
D)   calciteE) A) and B)
F) All of the above

Question 18

Which of the following is the major dissolved volatile constituent in both magmas and volcanic gases?

Accepted Answer

A)   methane
B)   water
C)   nitrous oxide
D)   carbon monoxideE) A) and D)
F) All of the above

Question 19

The molten portion of magmas and lavas is made up of_________ .

Accepted Answer

A)   silicate minerals that have already crystallized
B)   solid high pressure forms of water, carbon dioxide, and sulfur dioxide
C)   complex anion frameworks of oxygen with silicon and aluminum and cation modifiers made up of different amounts of calcium, sodium, iron, magnesium, and potassium
D)   metamorphic fluidsE) B) and C)
F) A) and D)

Question 20

_________is the dominant feldspar in basalt.

Accepted Answer

A)   Microcline
B)   Orthoclase
C)   Plagioclase
D)   PyroxeneE) All of the above
F) B) and D)

Exam 14: Mass Wasting: the Work of Gravity

What would you name a light pink, aphanitic, fragmental pyroclastic with sparse quartz phenocrysts?

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The molten portion of magmas and lavas is made up of_________ .

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Which texture would be most unlikely to occur in an extrusive igneous rock?

Correct AnswerverifiedShow Answer

Which statement best describes the crystallization of magmas?

Correct AnswerverifiedShow Answer

What small, intrusive igneous rock bodies often contain gem- quality crystals of minerals such as beryl and tourmaline and high concentrations of relatively rare elements such as lithium, cesium, and uranium?

Correct AnswerverifiedShow Answer

The main factors which directly govern the development of texture in all igneous rocks are________

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Which of the following is the major dissolved volatile constituent in both magmas and volcanic gases?

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_________is the dominant feldspar in basalt.

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Explosive volcanic eruptions occur___________ .

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What kind of coarse grained plutonic rock would you expect to find in the ocean crust underneath an undersea basaltic volcano?

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As melts cool their viscosity increases (they lose their mobility and get stiffer) even before they start to crystallize because_________ .

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Which of the following minerals crystallize early in Bowen's reaction series?

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The most common non- ferromagnesian silicate minerals (>40 %) in most igneous rocks are_________

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What two rock types are often found interlayered in the same volcanic deposit?

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Which of the following best describes an aphanitic texture?

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Felsic rocks like granite_______ .

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What is the most common extrusive rock type for any volcanic environment on the Earth or even on the Moon?

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Pyroxene, hornblende, and biotite are all minerals found on the ___________series of Bowen's Reaction Series.

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Felsic rocks have silica contents of______ are rich in______ .

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Mafic rocks have silica contents of __________and are mainly composed of_________ .

Correct AnswerverifiedShow Answer

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Felsic rocks have silica contents of are rich in .

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Mafic rocks have silica contents of __and are mainly composed of_ .

Correct Answer
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