Question 1

Why is peridote considered a coarse-grained ultramafic rock?

Accepted Answer

A)  It contains a lot of silica. 
B)  It contains a lot of feldspar. 
C)  It contains a medium amount of silica. 
D)  It contains very little silica. 
A)  It contains a lot of silica. 
B)  It contains a lot of feldspar. 
C)  It contains a medium amount of silica. 
D)  It contains very little silica.

Question 2

Name the type of volcano described here: "Thick, steep, lava-flow domes form these young volcanoes made of dacitic and rhyolitic rock."

Accepted Answer

A)  shield volcano 
B)  dome complex volcano 
C)  cinder cone volcano 
D)  composite volcano 
A)  shield volcano 
B)  dome complex volcano 
C)  cinder cone volcano 
D)  composite volcano

Question 3

What type of crystal texture is formed when magma cools slowly within warm rock underground?

Accepted Answer

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

Question 4

The lava at Kilauea volcano in Hawaii erupts at a temperature of approximately 1000 degrees Celsius. How could geologists overcome this problem when studying the lava flow?

Accepted Answer

A)  Pour water on the lava. 
B)  Don't bother studying the lava flow. 
C)  Take pictures from far away and study them in the lab. 
D)  Wear heat-resistant clothing and use tools that reach the flow from a few meters away. 
A)  Pour water on the lava. 
B)  Don't bother studying the lava flow. 
C)  Take pictures from far away and study them in the lab. 
D)  Wear heat-resistant clothing and use tools that reach the flow from a few meters away.

Question 5

What four processes result in the diversity of igneous rock? (4.7)

Accepted Answer

1. Different types of rock can melt or p

Question 6

What is an effect of a volcano with Rhyolitc magma?

Accepted Answer

A)  Rhyolitic magma has low gas content; volcanoes with this type of magma erupt gently. 
B)  Rhylotic magma has low viscosity; volcanoes with this type of magma erupt more often. 
C)  Rhyolitic magma has high gas content; volcanoes with this type of magma erupt violently. 
D)  Rhyolitic magma has low gas content; volcanoes with this type of magma erupt less often. 
A)  Rhyolitic magma has low gas content; volcanoes with this type of magma erupt gently. 
B)  Rhylotic magma has low viscosity; volcanoes with this type of magma erupt more often. 
C)  Rhyolitic magma has high gas content; volcanoes with this type of magma erupt violently. 
D)  Rhyolitic magma has low gas content; volcanoes with this type of magma erupt less often.

Question 7

Why is gabbro considered a coarse-grained mafic rock?

Accepted Answer

A)  It contains a lot of silica. 
B)  It is extremely rare. 
C)  It contains a lot of feldspar. 
D)  It contains a lot of magnesium and iron. 
A)  It contains a lot of silica. 
B)  It is extremely rare. 
C)  It contains a lot of feldspar. 
D)  It contains a lot of magnesium and iron.

Question 8

In which ways does pressure influence different rock compositions' melting points?

Accepted Answer

A)  the more pressure, the higher the melting point 
B)  the more pressure, the lower the melting point 
C)  pressure changes the composition of the rock, raising the melting point 
D)  pressure changes the composition of the rock, lowering the melting point 
A)  the more pressure, the higher the melting point 
B)  the more pressure, the lower the melting point 
C)  pressure changes the composition of the rock, raising the melting point 
D)  pressure changes the composition of the rock, lowering the melting point

Question 9

Why is tonalite considered a coarse-grained felsic rock?

Accepted Answer

A)  It contains very little silica. 
B)  It contains a lot of silica and feldspar. 
C)  It contains a lot of silica and magnesium. 
D)  It contains a lot of iron and magnesium. 
A)  It contains very little silica. 
B)  It contains a lot of silica and feldspar. 
C)  It contains a lot of silica and magnesium. 
D)  It contains a lot of iron and magnesium.

Question 10

Why is crystal size an important component in igneous rock texture?

Accepted Answer

A)  It shows if the rock formed underwater or underground. 
B)  It shows if the rock underwent metamorphism or lithification. 
C)  It shows what color the rock is. 
D)  It shows if the rock cooled underground or above ground. 
A)  It shows if the rock formed underwater or underground. 
B)  It shows if the rock underwent metamorphism or lithification. 
C)  It shows what color the rock is. 
D)  It shows if the rock cooled underground or above ground.

Question 11

Why are dissolved gases present in magma, but not lava?

Accepted Answer

A)  The gases condense to form liquids once magma hits the earth's surface. 
B)  The gases escape once magma hits the earth's surface. 
C)  The gases combust once magma hits the earth's surface. 
D)  The gases crystallize once magma hits the earth's surface. 
A)  The gases condense to form liquids once magma hits the earth's surface. 
B)  The gases escape once magma hits the earth's surface. 
C)  The gases combust once magma hits the earth's surface. 
D)  The gases crystallize once magma hits the earth's surface.

Question 12

How can you tell apart volcanic and plutonic rocks?

Accepted Answer

A)  Look at their fracturing properties. 
B)  Volcanic rocks are fine grained; plutonic rocks are coarse grained. 
C)  Volcanic rocks are colder than plutonic rocks. 
D)  Volcanic rocks are older than plutonic rocks. 
A)  Look at their fracturing properties. 
B)  Volcanic rocks are fine grained; plutonic rocks are coarse grained. 
C)  Volcanic rocks are colder than plutonic rocks. 
D)  Volcanic rocks are older than plutonic rocks.

Question 13

Names given to the different types of igneous intrusions are attributed to their

Accepted Answer

A)  shape and size. 
B)  composition and crystal size. 
C)  location and depth. 
D)  process of formation. 
A)  shape and size. 
B)  composition and crystal size. 
C)  location and depth. 
D)  process of formation.

Question 14

Briefly describe what makes volcano types different from one another and give an example of a type. (4.3)

Accepted Answer

Different magma compositions and types o

Question 15

Batholiths are larger than stocks.

Accepted Answer

A) True 
 B)False

Question 16

Why is dacite considered a fine-grained rock felsic rock?

Accepted Answer

A)  It contains very little silica. 
B)  It contains a lot of silica and feldspar. 
C)  It contains a lot of iron and magnesium. 
D)  It contains an intermediate amount of silica. 
A)  It contains very little silica. 
B)  It contains a lot of silica and feldspar. 
C)  It contains a lot of iron and magnesium. 
D)  It contains an intermediate amount of silica.

Question 17

Why are pyroclastic flows and lahars the most deadly and destructive volcanic phenomena? (4.9)

Accepted Answer

They are extremely fast-moving and far-f

Question 18

What is a benefit of ash and lapilli ejections?

Accepted Answer

A)  They produce highly fertile soil in tropical regions. 
B)  They contain extremely valuable minerals. 
C)  The chemicals cause extremely important rainfall in tropical regions. 
D)  They often rid farms of pests. 
A)  They produce highly fertile soil in tropical regions. 
B)  They contain extremely valuable minerals. 
C)  The chemicals cause extremely important rainfall in tropical regions. 
D)  They often rid farms of pests.

Question 19

Why would decompression of the mantle cause the production of mafic magma?

Accepted Answer

A)  Mafic magma is produced at high pressures. 
B)  With less pressure comes higher melting points. 
C)  Mafic magma is produced at low pressure. 
D)  With less pressure comes lower melting points. 
A)  Mafic magma is produced at high pressures. 
B)  With less pressure comes higher melting points. 
C)  Mafic magma is produced at low pressure. 
D)  With less pressure comes lower melting points.

Question 20

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

Accepted Answer

A)  He observed that the rock has a lot of silica, making it mafic. 
B)  He observed that the rock has a lot of silica, making it ultra-mafic. 
C)  He observed that the sample has little silica, making it felsic. 
D)  he observed that the sample has a lot of silica, making it felsic. 
A)  He observed that the rock has a lot of silica, making it mafic. 
B)  He observed that the rock has a lot of silica, making it ultra-mafic. 
C)  He observed that the sample has little silica, making it felsic. 
D)  he observed that the sample has a lot of silica, making it felsic.

Exam 4: Formation of Magma and Igneous Rocks

Why is peridote considered a coarse-grained ultramafic rock?

Name the type of volcano described here: "Thick, steep, lava-flow domes form these young volcanoes made of dacitic and rhyolitic rock."

What type of crystal texture is formed when magma cools slowly within warm rock underground?

The lava at Kilauea volcano in Hawaii erupts at a temperature of approximately 1000 degrees Celsius. How could geologists overcome this problem when studying the lava flow?

What four processes result in the diversity of igneous rock? (4.7)

What is an effect of a volcano with Rhyolitc magma?

Why is gabbro considered a coarse-grained mafic rock?

In which ways does pressure influence different rock compositions' melting points?

Why is tonalite considered a coarse-grained felsic rock?

Why is crystal size an important component in igneous rock texture?

Why are dissolved gases present in magma, but not lava?

How can you tell apart volcanic and plutonic rocks?

Names given to the different types of igneous intrusions are attributed to their

Briefly describe what makes volcano types different from one another and give an example of a type. (4.3)

Batholiths are larger than stocks.

Why is dacite considered a fine-grained rock felsic rock?

Why are pyroclastic flows and lahars the most deadly and destructive volcanic phenomena? (4.9)

What is a benefit of ash and lapilli ejections?

Why would decompression of the mantle cause the production of mafic magma?

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

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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