Question 1

What is an example of pyroclastic materials?

Accepted Answer

A)  Lava-fountain blobs 
B)  pumice 
C)  Lava-fountain blobs, pumice, and ash 
D)  ash 
A)  Lava-fountain blobs 
B)  pumice 
C)  Lava-fountain blobs, pumice, and ash 
D)  ash

Question 2

Why are igneous rocks that consist of coarse-grained crystals called phaneritic?

Accepted Answer

A)  Phaneritic comes from the Greek word aphaneros, meaning invisible. 
B)  They form deep within the ocean. 
C)  Phaneritic comes from the Greek word phaneros, meaning visible. 
D)  They are porphyritic rocks. 
A)  Phaneritic comes from the Greek word aphaneros, meaning invisible. 
B)  They form deep within the ocean. 
C)  Phaneritic comes from the Greek word phaneros, meaning visible. 
D)  They are porphyritic rocks.

Question 3

Volcanoes are present at convergent plate boundaries because

Accepted Answer

A)  the plates rub together, causing friction and heat. 
B)  water is carried down with the subducting plate and causes the mantle to melt. 
C)  heat from the inner mantle travels up along the subducting plate. 
D)  decompression melting due to decreased pressure at the boundary causes the mantle to melt and rise into volcano formations. 
A)  the plates rub together, causing friction and heat. 
B)  water is carried down with the subducting plate and causes the mantle to melt. 
C)  heat from the inner mantle travels up along the subducting plate. 
D)  decompression melting due to decreased pressure at the boundary causes the mantle to melt and rise into volcano formations.

Question 4

Figure 4.22  
-According to Figure 4.22 which types of volcanic rock can be found in composite volcanoes?

Accepted Answer

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

Question 5

A scientist at a canyon notices observes a dike cuts across the sedimentary layers. How did it get there?

Accepted Answer

A)  It was there before the layers; the layers built upon above and beneath it over millions of years. 
B)  There was an earthquake  a layer of igneous rock was thrust into the sedimentary layers.. 
C)  Magma rose from within the earth and intruded the sedimentary layers. 
D)  A piece of a volcano broke off beneath the earth.. 
A)  It was there before the layers; the layers built upon above and beneath it over millions of years. 
B)  There was an earthquake  a layer of igneous rock was thrust into the sedimentary layers.. 
C)  Magma rose from within the earth and intruded the sedimentary layers. 
D)  A piece of a volcano broke off beneath the earth..

Question 6

Despite their large size, batholiths are emplaced over a relatively short period of time.

Accepted Answer

A) True 
 B)False

Question 7

Which of the following is not a property of a cinder cone?

Accepted Answer

A)  usually less than 600 meters tall 
B)  typically produced by one, prolonged eruption 
C)  can be up to 10000 meters tall 
D)  composed of basaltic to andesitic cinder 
A)  usually less than 600 meters tall 
B)  typically produced by one, prolonged eruption 
C)  can be up to 10000 meters tall 
D)  composed of basaltic to andesitic cinder

Question 8

Many economically important metallic elements like gold and silver are disseminated throughout magma. Why are we able to mine these metals?

Accepted Answer

A)  They are easy to pick out of lava flows with tools that reach a few meters away. 
B)  They don't melt; they float in lava flows and are then trapped when the lava melts; humans go in and mine the lava flows. 
C)  They become concentrated by fractional crystallization into the last bit of the magma that remains after most of the silicate minerals have formed. 
D)  They float up to the surface of the lava and harden on top of the flow. 
A)  They are easy to pick out of lava flows with tools that reach a few meters away. 
B)  They don't melt; they float in lava flows and are then trapped when the lava melts; humans go in and mine the lava flows. 
C)  They become concentrated by fractional crystallization into the last bit of the magma that remains after most of the silicate minerals have formed. 
D)  They float up to the surface of the lava and harden on top of the flow.

Question 9

Which process forms a'a lava formations?

Accepted Answer

A)  Very thick lava squeezes out in large mounds. 
B)  Thin lava runs quickly over a large area. 
C)  Lava stops flowing while it is still hot and forms ropes. 
D)  Lava continues flowing after a crust forms. 
A)  Very thick lava squeezes out in large mounds. 
B)  Thin lava runs quickly over a large area. 
C)  Lava stops flowing while it is still hot and forms ropes. 
D)  Lava continues flowing after a crust forms.

Question 10

Highly vesicular, intermediate-sized pyroclastic fragments of dacite or rhyolite are called

Accepted Answer

A)  cinder. 
B)  pumice. 
C)  scoria. 
D)  lapilli. 
A)  cinder. 
B)  pumice. 
C)  scoria. 
D)  lapilli.

Question 11

A scientist identifies a rock sample as very rare. Why did he do so?

Accepted Answer

A)  He observed that the rock is fine grained and has a lot of silica, making it mafic. 
B)  He observed that the sample is fine grained and has very little silica, making it ultra-mafic. 
C)  He observed that the rock is coarse grained and has a lot of silica, making it ultra-mafic. 
D)  He observed that the rock is fine grained and has very little silica, making it felsic. 
A)  He observed that the rock is fine grained and has a lot of silica, making it mafic. 
B)  He observed that the sample is fine grained and has very little silica, making it ultra-mafic. 
C)  He observed that the rock is coarse grained and has a lot of silica, making it ultra-mafic. 
D)  He observed that the rock is fine grained and has very little silica, making it felsic.

Question 12

A student notes that a rock contains mica and plagioclase feldspar and concludes that the rock is an intermediate rock. What piece of further information could best determine if the student's conclusion was the correct one?

Accepted Answer

A)  the grain size of the crystals 
B)  the color of the rock 
C)  the amphibole content of the rock 
D)  the silicate content of the rock 
A)  the grain size of the crystals 
B)  the color of the rock 
C)  the amphibole content of the rock 
D)  the silicate content of the rock

Question 13

Why are lahars so dangerous?

Accepted Answer

A)  They are the hottest of all lava flows. 
B)  They contain deadly chemicals. 
C)  Hot pyroclastic fragments melt ice and snow; this mixture flows extremely fast. 
D)  They are the most explosive of all volcanic eruptions. 
A)  They are the hottest of all lava flows. 
B)  They contain deadly chemicals. 
C)  Hot pyroclastic fragments melt ice and snow; this mixture flows extremely fast. 
D)  They are the most explosive of all volcanic eruptions.

Question 14

Why do pyroclastic flows always have higher casualty tolls than lava flows?

Accepted Answer

A)  Pyroclasic flows are much hotter. 
B)  Lava flows are better predicted. 
C)  Pyroclastic flows occur more often. 
D)  Pyclastic flows move at velocities exceeding 100 km/hr. 
A)  Pyroclasic flows are much hotter. 
B)  Lava flows are better predicted. 
C)  Pyroclastic flows occur more often. 
D)  Pyclastic flows move at velocities exceeding 100 km/hr.

Question 15

Why don't all magmas erupt? (4.10)

Accepted Answer

When rocks partially melt, the resulting

Question 16

Why is diorite considered a coarse-grained intermediate rock?

Accepted Answer

A)  It contains a medium amount of silica. 
B)  It contains a lot of silica. 
C)  It contains very little silica. 
D)  It is made up of the elements in the middle of the periodic table. 
A)  It contains a medium amount of silica. 
B)  It contains a lot of silica. 
C)  It contains very little silica. 
D)  It is made up of the elements in the middle of the periodic table.

Question 17

Which of the following is considered an indirect volcanic hazard?

Accepted Answer

A)  lava flows 
B)  ash fall 
C)  lahars 
D)  tsunamis 
A)  lava flows 
B)  ash fall 
C)  lahars 
D)  tsunamis

Question 18

If volcanic rocks are formed on the earth's surface, what is another word for them?

Accepted Answer

A)  extrusive 
B)  intrusive 
C)  plutonic 
D)  lava 
A)  extrusive 
B)  intrusive 
C)  plutonic 
D)  lava

Question 19

The composition of the magma determines the minerals that form in an igneous rock.

Accepted Answer

A) True 
 B)False

Question 20

Which of the following causes the formation of large crystals such as pegmatite?

Accepted Answer

A)  high fluid content of magma 
B)  high heavy metal content of magma 
C)  high silica content of magma 
D)  high solidification factor of magma 
A)  high fluid content of magma 
B)  high heavy metal content of magma 
C)  high silica content of magma 
D)  high solidification factor of magma

Exam 4: Formation of Magma and Igneous Rocks

What is an example of pyroclastic materials?

Why are igneous rocks that consist of coarse-grained crystals called phaneritic?

Volcanoes are present at convergent plate boundaries because

Figure 4.22 -According to Figure 4.22 which types of volcanic rock can be found in composite volcanoes?

A scientist at a canyon notices observes a dike cuts across the sedimentary layers. How did it get there?

Despite their large size, batholiths are emplaced over a relatively short period of time.

Which of the following is not a property of a cinder cone?

Many economically important metallic elements like gold and silver are disseminated throughout magma. Why are we able to mine these metals?

Which process forms a'a lava formations?

Highly vesicular, intermediate-sized pyroclastic fragments of dacite or rhyolite are called

A scientist identifies a rock sample as very rare. Why did he do so?

A student notes that a rock contains mica and plagioclase feldspar and concludes that the rock is an intermediate rock. What piece of further information could best determine if the student's conclusion was the correct one?

Why are lahars so dangerous?

Why do pyroclastic flows always have higher casualty tolls than lava flows?

Why don't all magmas erupt? (4.10)

Why is diorite considered a coarse-grained intermediate rock?

Which of the following is considered an indirect volcanic hazard?

If volcanic rocks are formed on the earth's surface, what is another word for them?

The composition of the magma determines the minerals that form in an igneous rock.

Which of the following causes the formation of large crystals such as pegmatite?

Why Study Earth

Minerals: Building Blocks of the Planet

Rocks and Rock-Forming Processes

Formation of Sediment and Sedimentary Rocks

Formation of Metamorphic Rocks

Earth Materials As Time Keepers

Earth Materials As Time Keepers

Making Earth

Motion Inside Earth

Deformation of Rocks

Global Tectonics: Plates and Plumes

Tectonics and Surface Relief

Soil Formation and Landscape Stability

Mass Movements: Landscapes in Motion

Streams: Flowing Water Shapes the Landscape

Water Flowing Underground

Glaciers: Cold-Climate Sculptors of Continents

Shorelines: Changing Landscapes Where Land Meets Sea

Wind: a Global Geologic Process

Global Warming: Real Time Change in the Earth System

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