GM Questions Exam 1 Test with Complete Answers
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-olivi...
GM Questions Exam 1 Test
with Complete Answers
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
Which of the following best describes the difference between granite and rhyolite? -
Answer-Granite is phaneritic and rhyolite is aphanitic.
What is the rock name of an intermediate rock with two distinct grain sizes? - Answer-
Andesite porphyry
What do pumice and scoria have in common? - Answer-They both exhibit a vesicular
texture.
A ________ is a tabular, concordant pluton that is nearly horizontal and forms when
magma exploits a weakness between sedimentary layers. - Answer-sill
A ________ is a mushroom-shaped pluton that forms by injecting magma between
sedimentary strata, forcing the upper layers to arch upward. - Answer-laccolith
Which of the following is a characteristic of an igneous rock found in a batholith? -
Answer-phaneritic texture
What is the name of the preexisting rock through which intrusive igneous bodies
intrude? - Answer-Country rock
A dike is mostly likely to be composed of which of the following igneous rocks? -
Answer-basalt
Select the correct description of dikes and sills. - Answer-Dikes are discordant igneous
intrusions; sills are concordant igneous intrusions; both are tabular.
, How do batholiths, stocks, and laccoliths differ? - Answer-Batholiths are the largest type
of igneous bodies and occur in a linear fashion with a distance of 100km or more;
stocks are smaller than batholiths; laccoliths bend the sedimentary layers above them,
whereas the sedimentary layers below remain relatively undeformed.
To what does the term "country rock" refer? - Answer-the crustal rocks into which
igneous bodies intrude
Which of the following is true based off your observation of intrusive igneous rocks on
Earth's surface? - Answer-Intrusive igneous bodies are formed by magma intruding and
crystallizing in country rock below Earth's surface. Therefore, if we observe these
features at the surface today, they must be exposed by uplift and erosion.
What is the best interpretation for how the porphyritic texture of these rocks formed? -
Answer-The magma cooled slowly at first, forming large crystals, and then quickly,
forming small crystals from the remaining magma.
What is the difference between a dike and a sill? - Answer-Dikes crosscut sedimentary
layers; sills pry between horizontal layers.
Why are the dikes and sills so easily distinguished in Sinbad Country? - Answer-Basalt
and the hardened, baked zones are more resistant to erosion than the sedimentary
rocks.
Why are sills only located fairly close to the Earth's surface? - Answer-Sills form as
magma intrudes with enough force to overcome the weight of the rocks above.
Why don't the baked zones along the edges of the dikes and sills show evidence of
metamorphism? - Answer-They weren't under enough pressure and didn't remain hot
for a long enough period of time.
Approximately how long did it take for the magma that fed each dike in Sinbad Country
to be injected? - Answer-The magma was injected in a matter of hours to days.
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
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