Question 1

In a series of basaltic lava flows on Hawaii, the top and bottom of each flow is difficult to distinguish just by looking at the layers of rock. What are some rock characteristics (texture, mineralogy, etc.)and other features that you might use to recognize individual lava flows?

Accepted Answer

Crystal size, vesicu...

Question 2

________is characterized by very coarse mineral grains.

Accepted Answer

A)  Obsidian
B)  Pegmatite
C)  Pumice
D)  Granite

Question 3

All of the following are factors that affect the generation of magma EXCEPT for _________ .

Accepted Answer

A)  volatiles
B)  pressure
C)  crystal size
D)  heat

Question 4

What do pumice and obsidian have in common?

Accepted Answer

A)  ultramafic composition
B)  glassy texture
C)  basaltic composition
D)  phaneritic texture B

Question 5

________is the dominant lava erupted from volcanoes on Hawaii and Iceland.

Accepted Answer

A)  Basalt
B)  Peridotite
C)  Rhyolite
D)  Andesite

Question 6

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 too small to be visible without a magnifying lens or microscope.
C)  The mineral grains have glassy textures.
D)  The rock is crystalline; mineral grains are of distinctly different sizes.

Question 7

Which of the following igneous rocks exhibit aphanitic texture?

Accepted Answer

A)  rhyolite, gabbro
B)  andesite, diorite
C)  andesite, rhyolite
D)  granite, gabbro

Question 8

A(n)________texture refers to rocks composed mainly of mineral and volcanic fragments.

Accepted Answer

The answer of A(n)________texture refers to rocks composed mainly of...

Question 9

In a porphyritic volcanic rock, which mineral grains are the last to crystallize?

Accepted Answer

A)  vesicles
B)  pegmatites
C)  matrix or groundmass
D)  phenocrysts

Question 10

Technically, the process whereby ions arrange themselves into orderly patterns during the cooling of a liquid is called________ .

Accepted Answer

The answer of Technically, the process whereby ions arrange themselves...

Question 11

Consider Bowen's reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt?

Accepted Answer

A)  sodium- rich plagioclase
B)  olivine
C)  quartz
D)  orthoclase

Question 12

The last minerals to crystallize on Bowen's Reaction Series result in igneous rocks with a ________composition.

Accepted Answer

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

Question 13

Which igneous rock or magma has the lowest silica (SiO2 ) content?

Accepted Answer

A)  andesite
B)  granite
C)  peridotite
D)  basalt

Question 14

What magma- generating process is exhibited by the diagram below? When does this process take place?

Accepted Answer

Decompression melting. This occurs when confining pressure drops enough to lower melting points.
Such drops in pressure occur when rock ascends due to convective upwelling like that at divergent plate boundaries.

Question 15

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

Accepted Answer

A)  olivine
B)  biotite
C)  quartz
D)  muscovite

Question 16

Changing the composition of magma by incorporating surrounding host rock is known as________ .

Accepted Answer

A)  assimilation
B)  magma mixing
C)  differentiation
D)  partial melting

Question 17

Which of the following are used for studying rocks with a polarizing microscope?

Accepted Answer

A)  thin sections
B)  polished cubes
C)  broken chips
D)  grain karats

Question 18

________is the name given to molten rock below the Earth's surface.

Accepted Answer

The answer of ________is the name given to molten rock...

Question 19

A(n) ________texture represents a single, long period of cooling and crystallization.

Accepted Answer

A)  pyroclastic
B)  aphanitic
C)  phaneritic
D)  glassy

Question 20

Extrusive igneous rocks are typically finer grained than intrusive igneous rocks. Why?

Accepted Answer

A)  The extrusive magma, because it is deep below the surface, cools very slowly producing very small mineral grains.
B)  Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow.
C)  The extrusive magma cools quickly so the mineral grains do not have time to grow.
D)  Intrusive magma is cooler because it is well insulated by the surrounding rock. C

Exam 4: Igneous Rocks and Intrusive Activity

In a series of basaltic lava flows on Hawaii, the top and bottom of each flow is difficult to distinguish just by looking at the layers of rock. What are some rock characteristics (texture, mineralogy, etc.)and other features that you might use to recognize individual lava flows?

Correct AnswerverifiedCrystal size, vesicu...View AnswerShow Answer

________is characterized by very coarse mineral grains.

Correct AnswerverifiedShow Answer

All of the following are factors that affect the generation of magma EXCEPT for _________ .

Correct AnswerverifiedShow Answer

What do pumice and obsidian have in common?

Correct AnswerverifiedB

________is the dominant lava erupted from volcanoes on Hawaii and Iceland.

Correct AnswerverifiedShow Answer

Which of the following best describes an aphanitic texture?

Correct AnswerverifiedShow Answer

Which of the following igneous rocks exhibit aphanitic texture?

Correct AnswerverifiedShow Answer

A(n)________texture refers to rocks composed mainly of mineral and volcanic fragments.

Correct AnswerverifiedShow Answer

In a porphyritic volcanic rock, which mineral grains are the last to crystallize?

Correct AnswerverifiedShow Answer

Technically, the process whereby ions arrange themselves into orderly patterns during the cooling of a liquid is called________ .

Correct AnswerverifiedShow Answer

Consider Bowen's reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt?

Correct AnswerverifiedShow Answer

The last minerals to crystallize on Bowen's Reaction Series result in igneous rocks with a ________composition.

Correct AnswerverifiedShow Answer

Which igneous rock or magma has the lowest silica (SiO2 ) content?

Correct AnswerverifiedShow Answer

What magma- generating process is exhibited by the diagram below? When does this process take place?

Correct AnswerverifiedDecompression melting. This occurs when confining pressure drops enough to lower melting points. Such drops in pressure occur when rock ascends due to convective upwelling like that at divergent plate boundaries.

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

Correct AnswerverifiedShow Answer

Changing the composition of magma by incorporating surrounding host rock is known as________ .

Correct AnswerverifiedShow Answer

Which of the following are used for studying rocks with a polarizing microscope?

Correct AnswerverifiedShow Answer

________is the name given to molten rock below the Earth's surface.

Correct AnswerverifiedShow Answer

A(n) ________texture represents a single, long period of cooling and crystallization.

Correct AnswerverifiedShow Answer

Extrusive igneous rocks are typically finer grained than intrusive igneous rocks. Why?

Correct AnswerverifiedC

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Crystal size, vesicu...
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B

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Which igneous rock or magma has the lowest silica (SiO₂ ) content?

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Decompression melting. This occurs when confining pressure drops enough to lower melting points. Such drops in pressure occur when rock ascends due to convective upwelling like that at divergent plate boundaries.

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C