Question 1

Most volcanoes are found at or near divergent and convergent plate boundaries.

Accepted Answer

A) True 
 B)False  True

Question 2

The texture of an igneous rock consisting of coarse-grained crystals surrounded by very small crystals is called

Accepted Answer

A)  aphanitic. 
B)  phaneritic. 
C)  porphyritic. 
D)  glassy. 
A)  aphanitic. 
B)  phaneritic. 
C)  porphyritic. 
D)  glassy. C

Question 3

Which of the following is a difference between a shield volcano and a composite volcano?

Accepted Answer

A)  Shield volcanoes' lava flows are thin and long whereas composite volcanoes' lava flows are thicker and shorter. 
B)  Shield volcanoes have a much steeper slope than composite volcanoes. 
C)  Shield volcanoes are much hotter than composite volcanoes. 
D)  Shield volcanoes maximum height is much smaller than composite volcanoes. 
A)  Shield volcanoes' lava flows are thin and long whereas composite volcanoes' lava flows are thicker and shorter. 
B)  Shield volcanoes have a much steeper slope than composite volcanoes. 
C)  Shield volcanoes are much hotter than composite volcanoes. 
D)  Shield volcanoes maximum height is much smaller than composite volcanoes. A

Question 4

A scientist identifies a rock sample as andesite. 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 rock has a decent amount of silica, making it intermediate. 
D)  He observed that the sample has little 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 rock has a decent amount of silica, making it intermediate. 
D)  He observed that the sample has little silica, making it felsic.

Question 5

A volcanologist extracts a piece of rock near a volcano site and observes no visible crystals. After studying the rock for a while, he assumes it is obsidian. Why does he do so?

Accepted Answer

A)  Obsidian is always hot. 
B)  Obsidian forms underground. 
C)  Obsidian is green. 
D)  Obsidian forms in lava flows. 
A)  Obsidian is always hot. 
B)  Obsidian forms underground. 
C)  Obsidian is green. 
D)  Obsidian forms in lava flows.

Question 6

The lava at Kilauea volcano in Hawaii moves down slope at speeds of 1-10 meters per second; fast for a lava flow. What could account for this?

Accepted Answer

A)  The lava is spewing out of the cone at fast speeds. 
B)  The lava is more thin. 
C)  The lava is very thick. 
D)  The slope is steep. 
A)  The lava is spewing out of the cone at fast speeds. 
B)  The lava is more thin. 
C)  The lava is very thick. 
D)  The slope is steep.

Question 7

Why is plutonic a synonym of intrusive?

Accepted Answer

A)  Pluto was the Greek god of the sea; intrusive rock is formed in the sea. 
B)  They mean the same thing in everyday talk. 
C)  Pluto was the Greek god of the underworld; intrusive rock is formed underground. 
D)  Pluto was the Greek god of fire; intrusive rock is formed during volcanic eruption. 
A)  Pluto was the Greek god of the sea; intrusive rock is formed in the sea. 
B)  They mean the same thing in everyday talk. 
C)  Pluto was the Greek god of the underworld; intrusive rock is formed underground. 
D)  Pluto was the Greek god of fire; intrusive rock is formed during volcanic eruption.

Question 8

Highly vesicular, intermediate-sized pyroclastic fragments of basalt or andesite are called

Accepted Answer

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

Question 9

Why do felsic rocks typically have the lightest color?

Accepted Answer

A)  They contain olivine and pyroxene. 
B)  They contain pyroxene, amphibole, and plagioclase feldspar. 
C)  They contain quartz, mica, amphibole, sodium-rich plagioclase feldspar, and potassium feldspar. 
D)  They contain olivine, pyroxene, and calcium-rich plagioclase feldspar. 
A)  They contain olivine and pyroxene. 
B)  They contain pyroxene, amphibole, and plagioclase feldspar. 
C)  They contain quartz, mica, amphibole, sodium-rich plagioclase feldspar, and potassium feldspar. 
D)  They contain olivine, pyroxene, and calcium-rich plagioclase feldspar.

Question 10

Volcanic is a product of combustion.

Accepted Answer

A) True 
 B)False

Question 11

Which process forms pahoehoe 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 12

Why is methane gas the least abundant gas in magmas?

Accepted Answer

A)  Methane is only found deep within the earth. 
B)  Methane is repelled by heat. 
C)  Water vapor, carbon dioxide, and odorous sulfur compounds are the primary gases. 
D)  Methane turns to liquid in the presence of magma. 
A)  Methane is only found deep within the earth. 
B)  Methane is repelled by heat. 
C)  Water vapor, carbon dioxide, and odorous sulfur compounds are the primary gases. 
D)  Methane turns to liquid in the presence of magma.

Question 13

Volcanic bombs do not explode.

Accepted Answer

A) True 
 B)False

Question 14

A scientist identifies a rock sample as basalt. 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 little silica, making it mafic. 
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 little silica, making it mafic.

Question 15

Magma consists of oxides of silicon, aluminum, magnesium, iron, calcium, sodium and potassium. Why is this so?

Accepted Answer

A)  They are all heavy elements located beneath the surface of the earth. 
B)  They are all attracted to heat. 
C)  They all have low melting points. 
D)  They are all oxides. 
A)  They are all heavy elements located beneath the surface of the earth. 
B)  They are all attracted to heat. 
C)  They all have low melting points. 
D)  They are all oxides.

Question 16

Why is pegmatite an economically important igneous rock?

Accepted Answer

A)  Pegmatite's crystals are huge, so they are very valuable. 
B)  Pegmatite is very rare, so it is valuable. 
C)  Pegmatite's crystallization process causes the enrichment of rare ore minerals. 
D)  Pegmatite is perfect for the production of certain weaponry. 
A)  Pegmatite's crystals are huge, so they are very valuable. 
B)  Pegmatite is very rare, so it is valuable. 
C)  Pegmatite's crystallization process causes the enrichment of rare ore minerals. 
D)  Pegmatite is perfect for the production of certain weaponry.

Question 17

How do igneous products form and why do geologists study these processes? (4.1)

Accepted Answer

Igneous products form where magma crysta

Question 18

Briefly describe how igneous rocks are classified. (4.2)

Accepted Answer

Composition (minerals present) and textu

Question 19

Why is the texture of the igneous rock obsidian glassy?

Accepted Answer

A)  Obsidian commonly forms at the surface of lava flows. 
B)  Obsidian always forms beneath the earth's surface. 
C)  Obsidian is aphanitic. 
D)  Obsidian is phaneric. 
A)  Obsidian commonly forms at the surface of lava flows. 
B)  Obsidian always forms beneath the earth's surface. 
C)  Obsidian is aphanitic. 
D)  Obsidian is phaneric.

Question 20

Why are igneous rocks that form below earth's surface called plutonic rocks?

Accepted Answer

A)  Pluto was the Greek god of the underworld. 
B)  Igneous rocks formed underground are the same as those formed on Pluto. 
C)  Plutonic, in Latin, means intrusive. 
D)  Plutonic means non-eruptive, and intrusive rocks don't erupt. 
A)  Pluto was the Greek god of the underworld. 
B)  Igneous rocks formed underground are the same as those formed on Pluto. 
C)  Plutonic, in Latin, means intrusive. 
D)  Plutonic means non-eruptive, and intrusive rocks don't erupt.

Exam 4: Formation of Magma and Igneous Rocks

Most volcanoes are found at or near divergent and convergent plate boundaries.

The texture of an igneous rock consisting of coarse-grained crystals surrounded by very small crystals is called

Which of the following is a difference between a shield volcano and a composite volcano?

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

A volcanologist extracts a piece of rock near a volcano site and observes no visible crystals. After studying the rock for a while, he assumes it is obsidian. Why does he do so?

The lava at Kilauea volcano in Hawaii moves down slope at speeds of 1-10 meters per second; fast for a lava flow. What could account for this?

Why is plutonic a synonym of intrusive?

Highly vesicular, intermediate-sized pyroclastic fragments of basalt or andesite are called

Why do felsic rocks typically have the lightest color?

Volcanic is a product of combustion.

Which process forms pahoehoe lava formations?

Why is methane gas the least abundant gas in magmas?

Volcanic bombs do not explode.

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

Magma consists of oxides of silicon, aluminum, magnesium, iron, calcium, sodium and potassium. Why is this so?

Why is pegmatite an economically important igneous rock?

How do igneous products form and why do geologists study these processes? (4.1)

Briefly describe how igneous rocks are classified. (4.2)

Why is the texture of the igneous rock obsidian glassy?

Why are igneous rocks that form below earth's surface called plutonic rocks?

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

Filters