Earth Science: Geology, the Environment, and the Universe

Section 1: What are igneous rocks?

What Are Igneous Rocks?

1
Peridotite and dunite have __________ compositions.
A)felsic
B)mafic
C)ultramafic
D)intermediate
2
What is the source of heat inside Earth that melts rocks into magma?
A)geothermal energy
B)Earth's core is hotter for no reason.
C)the decay of radioactive elements
D)other molten rocks
3
Which is not a compositional classification of a magma?
A)basaltic
B)rhyolitic
C)andesitic
D)phaneritic
4
Extrusive rocks have fine-grained textures because __________.
A)they cooled inside Earth's crust
B)they cooled quickly
C)they cooled slow
D)they are derived from volcanoes
5
What is the last mineral to form on the left branch of Bowen's reaction series?
A)pyroxene
B)feldspar
C)olivine
D)quartz
6
Which rock has an intermediate composition?
A)rhyolite
B)diorite
C)dunite
D)basaltic
7
Granite is an example of __________ rock.
A)an extrusive igneous
B)a volcanic ash
C)an intrusive igneous
D)a partially melted
8
According to the figure, what happens to the melting point of rock as the depth and pressure increases?
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A)it decreases gradually
B)it decreases sharply
C)it increases gradually
D)it increases sharply
9
What process explains why a molten magma often is a mix of molten rock and crystals?
A)plate tectonics
B)melting points
C)partial melting
D)Bowen's reaction series
10
According to the figure showing a limited view of Bowen's reaction series, what type of mineral causes a continuous reaction series?
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A)magnesium
B)calcium
C)iron
D)sodium
11
What branch of Bowen's reaction series cools with a continuous change in composition?
A)the iron-magnesium groups
B)the carbonates
C)the feldspars
D)the silica chains
12
What is the temperature change in Earth's crust called?
A)geothermal gradient
B)radioactive decay
C)hydrothermal gradient
D)thermal energy
13
How are igneous rocks formed?
A)from the cementation of mineral grains
B)from the crystallization of magma
C)from increased pressures and temperatures
D)from the compaction of loose sediments
14
Oceanic crust melts at __________ than continental crust.
A)higher pressures and lower temperatures
B)higher temperatures
C)lower temperatures
D)the same temperature
15
Igneous rocks that cool on Earth's surface are called __________.
A)lava
B)molten
C)extrusive
D)intrusive
16
__________ explains the relationship between cooling magma and mineral formation.
A)Partial melting
B)Bowen's reaction series
C)Geothermal gradients
D)Branches of crystallization
17
What extrusive igneous rock has a mafic composition and a glassy texture?
A)diorite
B)basaltic glass
C)gabbro
D)obsidian
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