Deck 6: Up From the Inferno: Magma and Igneous Rocks

Question 1

A body of rock begins at location A in the figure below.The rock,over a period of time,moves to location B and begins to melt.This is an example of melting due to ________.

A)fractional crystallization
B)heat transfer
C)addition of volatiles
D)decompression

Answer 1

D

Question 2

Decay of 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 difference between magma and lava is ________.

A)magma cools more rapidly than lava
B)magma is found at the surface,whereas lava is found below the surface
C)magma is found beneath the surface,whereas lava is found at the surface
D)There is no difference;the two terms mean the same thing.

Answer 3

C

Question 4

In general,if a body of igneous (source)rock is subjected to partial melting,the magma that is produced is expected to be ________.

A)identical in chemical composition to the source rock
B)more mafic than the source rock
C)more felsic than the source rock
D)The melt composition is not predictable.

Question 5

Injecting hot fudge into ice cream and causing the ice cream to melt is an appropriate analogy for which cause of magma melt?

A)melting due to a decrease in pressure
B)melting due to an addition of volatiles
C)melting due to heat transfer from rising magma
D)flux melting

Question 6

Viscosity does NOT depend on ________.

A)temperature
B)volatile content
C)silica content
D)the total volume of the magma body

Question 7

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

Question 8

A majority of the melts in the Earth form through the partial melting of ultramafic mantle rock.These newly formed magmas are ________.

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

Question 9

Important volatiles in magmas include ________.

A)mafic minerals,such as olivine
B)potassium and aluminum
C)water and carbon dioxide
D)silicon and iron

Question 10

When magma crystallizes,________ are formed.

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

Question 11

Igneous rocks ________.

A)are formed through the freezing or crystallization of a melt
B)are formed by changing existing rock by the application of heat and pressure
C)are formed by depositing loose material into layers
D)form by chemically precipitating from solutions

Question 12

In general,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)

Question 13

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 14

Given the solidus and liquidus curves below,which location represents material that is partially melted?

A)A
B)B
C)C
D)D

Question 15

Very early in Earth's history (during the Hadean Eon),the Earth ________.

A)was very cold,so no igneous rocks had yet formed
B)was so hot that it was,at times,completely molten
C)was entirely composed of loose material called regolith
D)had a similar diversity in rock types as seen today

Question 16

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

A)increase
B)decrease
C)stay the same
D)Volatile content has no effect on viscosity.

Question 17

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)are highly flammable
D)have a tendency to evaporate into gases

Question 18

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 19

Which type of magma has the greatest silica content?

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

Question 20

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 21

All other factors equal,if a body of magma becomes more felsic,its viscosity will ________.

A)increase
B)decrease
C)stay the same
D)Chemical composition has no effect on viscosity.

Question 22

The silicate mineral that is found in the greatest variety of igneous rocks of various compositions is ________.

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

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

In the figure provided below,what type of igneous intrusion is the vertical rock unit shown by letter A?

A)dike
B)sill
C)pluton
D)laccolith

Question 25

A sill is a(n)________.

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

Question 26

An irregular-shaped and blob-like igneous rock body that cooled beneath the surface of Earth is ________.

A)a dike
B)pluton
C)a sill
D)a laccolith

Question 27

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

A)more felsic
B)more mafic
C)dominated by nonsilicate minerals
D)increasingly dense

Question 28

Which of the following is NOT a factor controlling the cooling rate of magma?

A)depth of intrusion
B)shape and size of magma body
C)presence of circulating groundwater
D)tectonic setting

Question 29

Plutons and batholiths are ________.

A)concordant igneous rocks derived from the cooling of mafic lava flows
B)regionally extensive discordant intrusive igneous rocks
C)small volcanic features developed from pyroclastic debris flows
D)igneous rock formations that cool extremely quickly

Question 30

In the figure provided below,what type of igneous intrusion is the horizontal rock unit shown by letter A?

A)dike
B)sill
C)pluton
D)laccolith

Question 31

A volcanic neck,such as that seen at Shiprock,New Mexico (below),is a(n)________.

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

Question 32

If you found tuff deposits at an ________ igneous setting,you could conclude that the source magma had a ________ viscosity.

A)intrusive;high
B)intrusive;low
C)extrusive;high
D)extrusive;low

Question 33

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)are less dense

Question 34

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 35

All other factors being equal (i.e.,depth,volume,temperature,etc.),which type of igneous intrusion would cool fastest?

A)pluton
B)dike
C)batholith
D)All intrusions cool at the same rate.

Question 36

In regard to the cooling of molten rock,a ________ volume and a ________ shape cool faster.

A)larger;spherical
B)larger;pancake
C)smaller;spherical
D)smaller;pancake

Question 37

Magma tends to ________.

A)move upward,away from where it formed
B)move downward,away from where it formed
C)move laterally
D)stay in one place

Question 38

If a body of magma is subjected to fractional crystallization,the first rock that is expected to crystallize from the magma will be ________.

A)identical in chemical composition to the magma
B)more mafic than the magma
C)more felsic than the magma
D)The composition of the rock is not predictable.

Question 39

Bowen's continuous reaction series describes the crystallization behavior of which single mineral (with variable chemical composition)?

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

Question 40

As compared to coarse-grained igneous rocks,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 41

Pegmatites,which often 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 42

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

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

Question 43

Bombs,ash,and cinders are all examples of ________.

A)intrusive igneous rocks
B)hot spots
C)volatiles
D)pyroclastic debris

Question 44

Which of the following is NOT a characteristic of the extrusive igneous rock obsidian?

A)It is composed of volcanic glass.
B)It possesses conchoidal fracture.
C)It is typically felsic in composition.
D)It likely cooled very slowly.

Question 45

Pillow basalts attain their distinctive blob-like shapes because their parent lavas do not travel far prior to solidification.This is because the parent lavas ________.

A)are completely devoid of volatiles and thus travel slowly
B)erupt underwater and thus cool very quickly
C)are highly felsic and thus travel slowly
D)are ultramafic and thus freeze at exceptionally high temperatures

Question 46

At which of the following does an island volcanic arc occur in the present day?

A)the Aleutian Islands of Alaska
B)the Andes Mountains
C)Hawaii
D)Mt.St.Helens,Washington

Question 47

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

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

Question 48

At which of the following does a continental volcanic arc occur in the present day?

A)the Aleutian Islands of Alaska
B)the Andes Mountains
C)Hawaii
D)Japan

Question 49

The presence of vesicles in an igneous rock is evidence that the source melt ________.

A)had a mafic composition
B)contained dissolved volatiles
C)underwent fractional crystallization
D)was stoping and assimilating wall rock

Question 50

Ash and lava fragments that cascade down the sides of a volcano eventually settle and lithify to form an extrusive igneous rock called ________.

A)basalt
B)andesite
C)hyaloclastite
D)tuff

Question 51

Large igneous provinces involve more than just the formation of large volumes of igneous rock.Which of the following global events has NOT been attributed to large igneous provinces?

A)sea-level rise
B)climate change
C)extinction
D)large outcrops of granite

Question 52

Vesicular is a term used to describe a texture in ________ igneous rocks.

A)crystalline
B)glassy
C)pyroclastic
D)intrusive

Question 53

The figure below shows mafic magma as it meets the seafloor,which cools to form an igneous rock called ________.

A)pegmatite
B)pillow basalt
C)laccolith
D)pluton

Question 54

Large igneous provinces are formed by ________,which can flow tens to hundreds of kilometers.

A)flood basalts
B)sills
C)super plumes
D)highly explosive eruptions

Question 55

At which of the following does a famous example of hot-spot volcanism occur?

A)the Aleutian Islands of Alaska
B)the Andes Mountains
C)Hawaii
D)Mt.St.Helens,Washington

Question 56

Mt.Kilimanjaro is an active volcano in Tanzania in eastern Africa that has formed as a result of ________.

A)converging plates
B)subducting plates
C)rifting
D)oceanic hot spots

Question 57

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

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

Question 58

Volcanoes that do NOT occur along either present or emergent plate boundaries are associated with ________.

A)continental rifts
B)hot spots
C)mid-ocean ridges
D)subduction zones

Question 59

As compared to aphanitic igneous rocks,phaneritic rocks are ________.

A)coarser grained
B)finer grained
C)more mafic
D)more felsic