Question 1

Light coloured aphanitic rocks ________.

Accepted Answer

A)  always form deep in the crust
B)  consist predominantly of small non-ferromagnesian minerals
C)  never form at the surface of the Earth
D)  consist predominantly of large ferromagnesian mineralsE) A) and B)
F) B) and C)

Question 2

Magmatic differentiation is the term geologists use for the classification and naming of igneous rocks.

Accepted Answer

A) True 
 B)False

Question 3

The size, shape, and geometric arrangement of mineral grains in igneous rocks is called ________ and it indicates ________.

Accepted Answer

A)  aphanitic form, how much water was present in the melt
B)  igneous geometry, the original % of partial melting
C)  geomorphology, depth of origin for the original magma
D)  texture, the environmental conditions in which the rock formedE) B) and C)
F) A) and C)

Question 4

The aphanitic equivalent of granite is

Accepted Answer

A)  rhyolite
B)  andesite
C)  basalt
D)  komatiiteE) None of the above
F) B) and D)

Question 5

Tabular sills and lava flows often have regular geometric grids of vertically oriented, thermal shrinkage cracks called ________.

Accepted Answer

A)  arthritic joints
B)  columnar joints
C)  hot flashes
D)  honeycomb fracturesE) A) and C)
F) B) and D)

Question 6

Three processes contribute to the formation of every igneous rock: ________.

Accepted Answer

A)  assimilation, crystallization, and dyke injection
B)  extrusion, intrusion, and consolidation
C)  partial melting, buoyant rise, and crystallization
D)  volcanism, plutonism, and magmatic differentiationE) A) and C)
F) A) and B)

Question 7

The phaneritic equivalent of basalt is

Accepted Answer

A)  gabbro
B)  granite
C)  diorite
D)  peridotiteE) A) and B)
F) B) and C)

Question 8

What would you name an intermediate coloured, coarse fragmental volcanic rock with large amphibole and plagioclase phenocrysts?

Accepted Answer

A)  hornblende andesite breccia
B)  hornblende granite porphyry
C)  hornblende diorite porphyry
D)  porphyritic hornblende gabbroE) A) and B)
F) All of the above

Question 9

Which of the following igneous rocks exhibit phaneritic texture?

Accepted Answer

A)  granite; tuff
B)  tuff; breccia
C)  basalt; pumice
D)  diorite; gabbroE) C) and D)
F) A) and B)

Question 10

Mafic rocks have silica contents of ________ and are mainly composed of ________.

Accepted Answer

A)  under 40%, olivine and pyroxene
B)  around 50%, pyroxene and plagioclase feldspar
C)  up to 70% quartz and feldspar
D)  more than 85%, potassium rich feldspars and micasE) None of the above
F) B) and D)

Question 11

What is/are thought to be the main mechanism(s) for generating basaltic melts from hot peridotite near its melting point in the upper mantle?

Accepted Answer

A)  conductive heating of basaltic ocean crust subducted into the mantle
B)  frictional heating of basaltic ocean crust as it slides down subduction zones
C)  intrusion of hotter solid mantle rocks from below
D)  drop of confining pressure or introduction of waterE) A) and C)
F) B) and C)

Question 12

What igneous texture refers to rocks composed mainly of mineral and volcanic fragments?

Accepted Answer

The answer of What igneous texture refers to rocks composed...

Question 13

________ is composed mainly of ferromagnesian minerals.

Accepted Answer

A)  Peridotite
B)  Rhyolite
C)  Andesite
D)  GraniteE) A) and D)
F) B) and C)

Question 14

Which of the following igneous rocks usually exhibit aphanitic texture?

Accepted Answer

A)  granite, gabbro
B)  andesite, rhyolite
C)  andesite, diorite
D)  rhyolite, gabbroE) A) and B)
F) A) and C)

Question 15

What phenocryst minerals would you expect to find in an aphanitic rhyolite flow?

Accepted Answer

A)  quartz and K-feldspar
B)  intermediate (Ca-Na) plagioclase and amphibole or pyroxene
C)  Ca-rich plagioclase and olivine
D)  apatite and muscoviteE) B) and D)
F) All of the above

Question 16

Match the description with the appropriate texture.
-________ mineral grains are of roughly equal size and coarse enough to be seen without a microscope or magnifying glass

Accepted Answer

A)  aphanitic 
B)  porphyritic 
C)  phaneritic 
D)  glassE) A) and B)
F) A) and C)

Question 17

How much silica do felsic igneous rocks commonly contain?

Accepted Answer

The answer of How much silica do felsic igneous rocks...

Question 18

Match the description with the appropriate texture.
-________ magma cools and consolidates without growth of mineral grains

Accepted Answer

A)  aphanitic 
B)  porphyritic 
C)  phaneritic 
D)  glassE) C) and D)
F) A) and B)

Question 19

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 20

Melting of rocks to form magma as a result of decreased pressure is known as ________.

Accepted Answer

decompress...

Exam 3: Igneous Rocks

Match the description with the appropriate texture. -________ mineral grains are of roughly equal size and coarse enough to be seen without a microscope or magnifying glass

Correct AnswerverifiedShow Answer

What phenocryst minerals would you expect to find in an aphanitic rhyolite flow?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The aphanitic equivalent of granite is

Correct AnswerverifiedShow Answer

What is/are thought to be the main mechanism(s) for generating basaltic melts from hot peridotite near its melting point in the upper mantle?

Correct AnswerverifiedShow Answer

Light coloured aphanitic rocks ________.

Correct AnswerverifiedShow Answer

Which of the following igneous rocks exhibit phaneritic texture?

Correct AnswerverifiedShow Answer

Three processes contribute to the formation of every igneous rock: ________.

Correct AnswerverifiedShow Answer

Match the description with the appropriate texture. -________ magma cools and consolidates without growth of mineral grains

Correct AnswerverifiedShow Answer

Tabular sills and lava flows often have regular geometric grids of vertically oriented, thermal shrinkage cracks called ________.

Correct AnswerverifiedShow Answer

Melting of rocks to form magma as a result of decreased pressure is known as ________.

Correct Answerverifieddecompress...View AnswerShow Answer

The size, shape, and geometric arrangement of mineral grains in igneous rocks is called ________ and it indicates ________.

Correct AnswerverifiedShow Answer

Mafic rocks have silica contents of ________ and are mainly composed of ________.

Correct AnswerverifiedShow Answer

Magmatic differentiation is the term geologists use for the classification and naming of igneous rocks.

Correct AnswerverifiedShow Answer

What igneous texture refers to rocks composed mainly of mineral and volcanic fragments?

Correct AnswerverifiedShow Answer

What would you name an intermediate coloured, coarse fragmental volcanic rock with large amphibole and plagioclase phenocrysts?

Correct AnswerverifiedShow Answer

How much silica do felsic igneous rocks commonly contain?

Correct AnswerverifiedShow Answer

________ is composed mainly of ferromagnesian minerals.

Correct AnswerverifiedShow Answer

Which of the following igneous rocks usually exhibit aphanitic texture?

Correct AnswerverifiedShow Answer

The phaneritic equivalent of basalt is

Correct AnswerverifiedShow Answer

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decompress...
View Answer

The size, shape, and geometric arrangement of mineral grains in igneous rocks is called and it indicates .

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Mafic rocks have silica contents of and are mainly composed of .

Correct Answer
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