GM questions Exam 1 with 100% correct
answers 2024
Which of the following textures indicates that a rock is of intrusive origin? - ANSWER-
Phaneritic
Which of the following textures indicates that a rock is volcanic in origin? - ANSWER-
Aphanitic
Which igneous texture has visible crystals that are a few millimeters across? -
ANSWER-Phaneritic
What is the geologic definition of texture? - ANSWER-Size, shape, and arrangement of
mineral grains in the sample
What creates the small holes found in a vesicular texture? - ANSWER-Volatiles
What substance makes ion migration easier in the later stages of magma crystallization,
which allows abnormally large mineral crystals to form and create pegmatites? -
ANSWER-water
Which of the following best describes a pegmatitic texture? - ANSWER-Large crystals
that form in a fluid-rich environment late in crystallization
has a large percentage of voids and is lightweight, so therefore has the ability to float in
water. - ANSWER-pumice
An igneous rock with a ______ texture solidified deep within Earth. - ANSWER-
Phaneritic
What factors influences the texture of an igneous rock? - ANSWER--the rate at which
the rock cools,
-the amount of silica that is present in the magma from which it forms, and
, -the amount of dissolved gases present in said magma
How do crystals in pegmatite grow so large? - ANSWER-Large crystals in pegmatites
are the result of a high percentage of the melt being composed of water, carbon dioxide,
and other materials. These materials enhance ion migration, allowing the crystals to
grow larger than usual.
What does a porphyritic texture indicate about the cooling history of an igneous rock? -
ANSWER-The rock began cooling under the Earth's surface, but then was moved to
above the Earth's surface where it finished cooling.
What is one way a glassy texture forms? - ANSWER-Lava cools rapidly.
Which of the following textures describes an igneous rock with anomalously large
crystals? - ANSWER-Pegmatitic
What does an igneous rock with a pyroclastic texture tell a geologist? - ANSWER-The
rock was likely formed by a violent volcanic eruption.
Which of the following textures indicates two stages of cooling and crystallization? -
ANSWER-Porphyritic
What large, overall igneous feature makes up the Sierra Nevada Mountains in
California? - ANSWER-batholith
What is a roof pendant? - ANSWER-older rock capping the batholith. This rock would
have been the roof of the magma chamber.
How do sheet joints and exfoliation domes form in granite plutons? - ANSWER-
Confining pressure on the plutons is removed through erosion of surrounding rock.
Plutons then expand.
Why is the monolith El Capitan in Yosemite National Park more resistant to erosion than
other igneous plutons in the park? - ANSWER-El Capitan is unfractured.
Ultramafic rocks contain __________ and are commonly found in __________. -
ANSWER-olivine; mantle
What is an accessory mineral? - ANSWER-A mineral that makes up a relatively small
portion of the total rock composition
answers 2024
Which of the following textures indicates that a rock is of intrusive origin? - ANSWER-
Phaneritic
Which of the following textures indicates that a rock is volcanic in origin? - ANSWER-
Aphanitic
Which igneous texture has visible crystals that are a few millimeters across? -
ANSWER-Phaneritic
What is the geologic definition of texture? - ANSWER-Size, shape, and arrangement of
mineral grains in the sample
What creates the small holes found in a vesicular texture? - ANSWER-Volatiles
What substance makes ion migration easier in the later stages of magma crystallization,
which allows abnormally large mineral crystals to form and create pegmatites? -
ANSWER-water
Which of the following best describes a pegmatitic texture? - ANSWER-Large crystals
that form in a fluid-rich environment late in crystallization
has a large percentage of voids and is lightweight, so therefore has the ability to float in
water. - ANSWER-pumice
An igneous rock with a ______ texture solidified deep within Earth. - ANSWER-
Phaneritic
What factors influences the texture of an igneous rock? - ANSWER--the rate at which
the rock cools,
-the amount of silica that is present in the magma from which it forms, and
, -the amount of dissolved gases present in said magma
How do crystals in pegmatite grow so large? - ANSWER-Large crystals in pegmatites
are the result of a high percentage of the melt being composed of water, carbon dioxide,
and other materials. These materials enhance ion migration, allowing the crystals to
grow larger than usual.
What does a porphyritic texture indicate about the cooling history of an igneous rock? -
ANSWER-The rock began cooling under the Earth's surface, but then was moved to
above the Earth's surface where it finished cooling.
What is one way a glassy texture forms? - ANSWER-Lava cools rapidly.
Which of the following textures describes an igneous rock with anomalously large
crystals? - ANSWER-Pegmatitic
What does an igneous rock with a pyroclastic texture tell a geologist? - ANSWER-The
rock was likely formed by a violent volcanic eruption.
Which of the following textures indicates two stages of cooling and crystallization? -
ANSWER-Porphyritic
What large, overall igneous feature makes up the Sierra Nevada Mountains in
California? - ANSWER-batholith
What is a roof pendant? - ANSWER-older rock capping the batholith. This rock would
have been the roof of the magma chamber.
How do sheet joints and exfoliation domes form in granite plutons? - ANSWER-
Confining pressure on the plutons is removed through erosion of surrounding rock.
Plutons then expand.
Why is the monolith El Capitan in Yosemite National Park more resistant to erosion than
other igneous plutons in the park? - ANSWER-El Capitan is unfractured.
Ultramafic rocks contain __________ and are commonly found in __________. -
ANSWER-olivine; mantle
What is an accessory mineral? - ANSWER-A mineral that makes up a relatively small
portion of the total rock composition
