Question 1

A sample contains 60 % Plagioclase Feldspar and a medium amount of silica. What would you call it?

Accepted Answer

A)   an intermediate igneous rock
B)   a mafic igneous rock
C)   an ultramafic igneous rock
D)   a felsic igneous rockE) A) and B)
F) A) and C)

Question 2

Why do igneous rocks have so many uses (anything from building stone to abrasive in toothpaste) ?

Accepted Answer

A)   They are harmful to the environment, so we use them to prevent harm done.
B)   They are very easy to attain.
C)   They are strong because their finely intergrown mineral crystals are difficult to fracture along grain boundaries.
D)   They are cheap.E) A) and C)
F) B) and C)

Question 3

Why are rocks rich in feldspar and silica called felsic?

Accepted Answer

A)   Felsic is the Latin word that means rich in feldspar and silica.
B)   Felsic is the opposite of mafic.
C)   Felsic comes from feldspar and silica.
D)   Felsic is the opposite of ultramafic.E) B) and D)
F) B) and C)

Question 4

Volcanoes composed of multiple, overlapping volcanic domes are called a

Accepted Answer

A)   dome complex.
B)   shield volcano.
C)   composite volcano.
D)   cinder cone.E) B) and C)
F) All of the above

Question 5

Figure 4.22 
-According to Figure 4.22 which types of magma form cinder cones?

Accepted Answer

A)   Basaltic, Andesitic, and Dacitic
B)   Basaltic, Andesitic, Dacitic and Rhyolitic
C)   Basaltic and Andesitic
D)   BasalticE) A) and D)
F) C) and D)

Question 6

Which igneous rocks are typically the lightest in color?

Accepted Answer

A)   ultramafic
B)   felsic
C)   intermediate
D)   maficE) None of the above
F) A) and B)

Question 7

Figure 4.22 
-According to Figure 4.22 which types of magma can erupt as lava flows?

Accepted Answer

A)   Basaltic, Andesitic, and Dacitic
B)   Basaltic, Andesitic, Dacitic and Rhyolitic
C)   Basaltic and Andesitic
D)   BasalticE) A) and C)
F) A) and D)

Question 8

What process forms rocks with porphyritic texture?

Accepted Answer

A)   quick cooling above ground
B)   slow cooling below ground
C)   a mixture of quick and slow cooling as rock moves from a warmer environment to a cooler one
D)   slow cooling combined with pressure undergroundE) B) and C)
F) None of the above

Question 9

Why does Silica content in most magmas range from 45 to almost 80 percent by weight?

Accepted Answer

A)   Silica is very heavy and therefore throws off the percent weight.
B)   Silica is made up of silicon and oxygen, two elements most prevalent in the earth's crust.
C)   Silica is a very heavy gas.
D)   Silica is extremely light.E) A) and B)
F) A) and C)

Question 10

Why are rocks rich in magnesium and iron called mafic?

Accepted Answer

A)   Mafic is the opposite of felsic.
B)   Ferric is the same as mafic, which means rich in magnesium and iron.
C)   Mafic comes from magnesium and ferric.
D)   Mafic is the Latin word that means rich is magnesium and iron.E) None of the above
F) A) and B)

Question 11

Which is not a danger associated with volcanic ash?

Accepted Answer

A)   Ash gets caught in jet engines causing them to fail.
B)   Ash can set fire to everything it falls on.
C)   Ash can cause roofs to collapse.
D)   Ash, if exposed to enough heat, can turn back to lava.E) A) and C)
F) B) and D)

Question 12

How and why do rocks melt? (4.4)

Accepted Answer

Rocks melt gradually as the melting temp...

Question 13

Why does Basaltic magma have the lowest viscosity?

Accepted Answer

A)   Basaltic lava has more silicate.
B)   Basaltic lava has less silicate.
C)   Basaltic lava is hotter than other flows.
D)   Basaltic lava is less hot than other flows.E) C) and D)
F) B) and C)

Question 14

Why are there different types of volcanoes and different volcanic eruptions? (4.8)

Accepted Answer

Volcanic phenomena and volcanic landform...

Question 15

What did Tuttle and Bowen observe in their experiment that helps geologists try to understand how magma is made? (4.5)

Accepted Answer

The melting temperature of granite is mu...

Question 16

Igneous rocks are overwhelmingly composed of silicate minerals. Why is this so?

Accepted Answer

A)   Silicates are very heavy.
B)   Silicates compose a huge amount of the earth's crust.
C)   Silicates are only found in igneous rocks.
D)   Silicates are very rare.E) All of the above
F) C) and D)

Question 17

All igneous rocks exhibit identical grain size.

Accepted Answer

A) True 
 B)False

Question 18

Why is granite considered a coarse-grained felsic rock?

Accepted Answer

A)   It contains a lot of feldspar and silica.
B)   It contains little feldspar and silica.
C)   It contains a lot of magnesium and iron.
D)   It contains a lot of feldspar and a little silica.E) All of the above
F) B) and C)

Question 19

A geologist looks at a piece of rock from Yosemite National Park under a microscope and sees tiny crystals of olivine, pyroxene, and plagioclase feldspar. What process might have formed this rock?

Accepted Answer

A)   melting underground, violent volcanic eruption, and solidification above ground
B)   melting underground, flowing to Earth's surface, and solidification above ground
C)   solidification underground, violent volcanic eruption of ash and solid rock
D)   both melting and crystallization undergroundE) B) and C)
F) A) and C)

Question 20

Which minerals usually give mafic and ultramafic rocks their dark colors?

Accepted Answer

A)   plagioclase feldspar and pyroxene
B)   amphibole and pyroxene
C)   olivine and pyroxene
D)   plagioclase feldspar and olivineE) B) and C)
F) None of the above

Exam 4: Formation of Magma and Igneous Rocks

What process forms rocks with porphyritic texture?

Correct AnswerverifiedShow Answer

Which is not a danger associated with volcanic ash?

Correct AnswerverifiedShow Answer

Why do igneous rocks have so many uses (anything from building stone to abrasive in toothpaste) ?

Correct AnswerverifiedShow Answer

Why are rocks rich in feldspar and silica called felsic?

Correct AnswerverifiedShow Answer

Why are there different types of volcanoes and different volcanic eruptions? (4.8)

Correct AnswerverifiedVolcanic phenomena and volcanic landform...View AnswerShow Answer

A geologist looks at a piece of rock from Yosemite National Park under a microscope and sees tiny crystals of olivine, pyroxene, and plagioclase feldspar. What process might have formed this rock?

Correct AnswerverifiedShow Answer

Why does Silica content in most magmas range from 45 to almost 80 percent by weight?

Correct AnswerverifiedShow Answer

Why are rocks rich in magnesium and iron called mafic?

Correct AnswerverifiedShow Answer

Figure 4.22 -According to Figure 4.22 which types of magma form cinder cones?

Correct AnswerverifiedShow Answer

All igneous rocks exhibit identical grain size.

Correct AnswerverifiedShow Answer

What did Tuttle and Bowen observe in their experiment that helps geologists try to understand how magma is made? (4.5)

Correct AnswerverifiedThe melting temperature of granite is mu...View AnswerShow Answer

Which minerals usually give mafic and ultramafic rocks their dark colors?

Correct AnswerverifiedShow Answer

Figure 4.22 -According to Figure 4.22 which types of magma can erupt as lava flows?

Correct AnswerverifiedShow Answer

A sample contains 60 % Plagioclase Feldspar and a medium amount of silica. What would you call it?

Correct AnswerverifiedShow Answer

Why is granite considered a coarse-grained felsic rock?

Correct AnswerverifiedShow Answer

Igneous rocks are overwhelmingly composed of silicate minerals. Why is this so?

Correct AnswerverifiedShow Answer

Why does Basaltic magma have the lowest viscosity?

Correct AnswerverifiedShow Answer

Volcanoes composed of multiple, overlapping volcanic domes are called a

Correct AnswerverifiedShow Answer

Which igneous rocks are typically the lightest in color?

Correct AnswerverifiedShow Answer

How and why do rocks melt? (4.4)

Correct AnswerverifiedRocks melt gradually as the melting temp...View AnswerShow Answer

Correct Answer
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Volcanic phenomena and volcanic landform...
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Correct Answer
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Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
The melting temperature of granite is mu...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
Rocks melt gradually as the melting temp...
View Answer