Deck 4: Up From the Inferno: Magma and Igneous Rocks

Question 1

When rock is partially melted,the chemistry of the melt is ____________.

A) more mafic than the original chemistry of the rock that was partially melted
B) more felsic than the original chemistry of the rock that was partially melted
C) identical to the original chemistry of the rock that was partially melted
D) completely unpredictable (it could be more mafic or more felsic)

Answer 1

B

Question 2

Radioactive isotopes,differentiation of Earth's iron core,gravity-driven compression,and meteoric bombardment all caused early Earth to ____________.

A) glow brighter than the Sun
B) be much cooler than at present
C) be much hotter than at present
D) be much more oblong than at present

Answer 2

C

Question 3

The formation of magma within Earth is NOT caused by which of the following processes?

A) decompression (drop in pressure)
B) addition of volatiles
C) transfer of heat from adjacent magma or very hot rocks
D) loss of volatiles to the atmosphere

Answer 3

D

Question 4

Volatiles refer to substances that ____________.

A) crystallize most rapidly out of a melt
B) melt immediately upon contact with a hot body of magma
C) have a tendency to evaporate and are stable as gases

Question 5

Igneous rocks ____________.

A) are formed through the freezing of melt
B) can be produced at the surface of the Earth as well as deep below the surface
C) are the most common type of rocks within Earth
D) all of the above

Question 6

A blob-like igneous rock body that has cooled beneath the surface of Earth is called a ____________.

A) guyot
B) pluton
C) lava flow
D) andesite

Question 7

If a body of magma becomes more felsic,its viscosity will ____________.

A) increase
B) decrease
C) stay the same

Question 8

A dike is ____________.

A) a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock
B) a cooled layer of lava
C) an intrusion formed within the magma chamber of a volcano
D) a sheetlike intrusion that cuts across preexisting layers

Question 9

Geologically,melts are equivalent to both ____________.

A) felsic and mafic magmas
B) felsic and mafic lavas
C) lavas and magmas
D) fine-grained and coarse-grained igneous rocks

Question 10

When magma crystallizes,____________ are formed.

A) intrusive igneous rocks C. volatiles
B) extrusive igneous rocks D. pyroclastic debris

Question 11

Very early in Earth's history,it was so hot that the surface was likely entirely molten.

Question 12

A sill is ____________.

A) a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock
B) a cooled layer of lava
C) an intrusion formed within the magma chamber of a volcano
D) a sheetlike intrusion that cuts across preexisting layers

Question 13

Due to fractional crystallization and assimilation of surrounding host rock,most magmas that rise slowly through the crust evolve chemically to become ____________.

A) more felsic
B) more mafic
C) dominated by nonsilicate minerals

Question 14

If a body of magma is subjected to fractional crystallization,the rock that results is expected to be ____________.

A) identical in chemical composition to the magma
B) more mafic than the magma
C) more felsic than the magma

Question 15

All of the Earth's internal heat was acquired very early in its history through meteoric impact and differentiation of the core.The Earth's interior loses heat to space but does not currently receive heat through any known process.

Question 16

The difference between lava and magma is that ____________.

A) magma is light in color and lava is dark
B) magma usually has mafic composition and lava usually has felsic composition
C) magma is found beneath the Earth's surface, whereas lava has reached the surface
D) magma flows more quickly than lava

Question 17

A volcano emits ash,which falls from the sky,settles in layers,and is eventually cemented.The resultant rock is termed ____________.

A) pumice
B) granite
C) tuff
D) ignimbrite

Question 18

If the volatile content of magma is increased,its viscosity will ____________.

A) increase
B) decrease
C) stay the same

Question 19

As compared to coarse-grained igneous rocks,all fine-grained igneous rocks ____________.

A) cool and solidify more quickly
B) cool and solidify more slowly
C) solidify at higher temperatures
D) solidify at lower temperatures

Question 20

The geotherm is the rate of change of ____________.

A) pressure with depth in Earth's interior
B) temperature with depth in Earth's interior
C) temperature with altitude in Earth's atmosphere
D) temperature with latitude on Earth's surface

Question 21

Bowen's continuous reaction series describes the crystallization behavior of a single mineral (with variable chemical composition),____________.

A) olivine
B) plagioclase
C) pyroxene
D) quartz

Question 22

Pegmatites,which occur in dikes,are unusual among shallow intrusive rocks in that they ____________.

A) possess porphyritic texture
B) possess exceptionally coarse grains
C) are mineralogically identical to the extrusive rock basalt
D) are glassy, cooling so rapidly that crystals do not have time to form

Question 23

In Bowen's discontinuous reaction series,the first mineral to crystallize from a mafic melt is ____________.

A) olivine
B) plagioclase
C) pyroxene
D) quartz

Question 24

Coarse-grained gabbro is most similar in mineral composition to fine-grained ____________.

A) andesite
B) basalt
C) komatiite
D) rhyolite

Question 25

As compared to mafic igneous rocks,all felsic igneous rocks ____________.

A) cool and solidify more quickly
B) cool and solidify more slowly
C) solidify at higher temperatures
D) solidify at lower temperatures

Question 26

Coarse-grained diorite is most similar in mineral composition to fine-grained ____________.

A) andesite
B) basalt
C) komatiite
D) rhyolite

Question 27

All other factors being equal,intrusive rocks that form deep within Earth ____________ than intrusive rocks that cool near the surface.

A) are more felsic
B) contain a smaller proportion of volatiles
C) cool more slowly
D) cool more rapidly

Question 28

Obsidian ____________.

A) is volcanic glass
B) possesses conchoidal fracture
C) typically is felsic in composition
D) all of the above

Question 29

Important volatiles in magmas include ____________.

A) iron- and magnesium-rich minerals, such as olivine
B) potassium and aluminum
C) water and carbon dioxide
D) trinitrotoluene and nitroglycerin

Question 30

Which type of magma has the greatest silica content?

A) felsic
B) intermediate
C) mafic
D) ultramafic

Question 31

Most commonly,felsic igneous rocks ____________.

A) contain more iron and magnesium than intermediate rocks
B) are lighter in color than mafic rocks
C) are darker in color than mafic rocks
D) are found in oceanic crust

Question 32

Coarse-grained granite is most similar in mineral composition to fine-grained ____________.

A) andesite
B) basalt
C) komatiite
D) rhyolite

Question 33

Stoping by magmas occurs when ____________.

A) pieces of surrounding country rock are broken off and assimilated
B) the magma stops flowing and starts to solidify
C) the magma becomes fully solidified to form intrusive rock
D) the magma alters a thin rind of surrounding country rock

Question 34

When rock is melted within Earth,typically the entire volume of rock is transformed from a solid state to a liquid.

Question 35

An igneous rock with a mixed texture of coarse grains (phenocrysts)surrounded by fine crystals (groundmass)is termed ____________.

A) porphyritic
B) phaneritic
C) aphanitic
D) necrotic