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Geology Final
Chapter 3
37
Geology
Undergraduate 2
12/10/2012

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Term
Lava is magma on the Earth's surface
Definition
True
Term
Extrusive igneous rocks are typically fine grained because they crystallized slowly, deep below the Earth's surface.
Definition
False
Term
A dike is a discordant intrusive igneous structure.
Definition
True
Term
The geothermal gradient is the rate at which pressure increases with increasing depth beneath the surface.
Definition
False
Term
Mafic igneous rocks are silica-poor.
Definition
True
Term
A mineral's melting point generally increases with increasing pressure.
Definition
True
Term
The sequence in which minerals crystallize in a cooling igneous melt is called Bowen's Reaction Series.
Definition
True
Term
A pluton is an igneous structure that crystallized at very shallow depths.
Definition
False
Term
Partial melting of the lower continental crust produces a silicic magma that eventually solidifies into granite or rhyolite.
Definition
True
Term
An ultramafic rock is composed almost entirely of quartz.
Definition
False
Term
The geothermal gradient for a volcanic region is greater than that for the continental interior.
Definition
True
Term
Pegmatites are extremely coarse-grained igneous rocks.
Definition
True
Term
Basaltic magmas crystallize at higher temperatures than granitic magmas.
Definition
True
Term
Igneous rocks may be either ____ if they form on or near Earth's surface, or ___ if they solidify under ground.
Definition
extrusive; intrusive
Term
______ igneous rocks, like gabbro and basalt, are silica-deficient with high magnesium and iron.
Definition
Mafic
Term
___ is a coarse-grained igneous rock (grains > 1 mm diameter) with visible grains of quartz.
Definition
Granite
Term
Fine-grained igneous rocks (grains < 1.0 mm) that have small grains cooled rapidly and are likely to be _______.
Definition
extrusive
Term
A _______ is a tabular (thin but large area) intrusive body that is concordant (parallel to the host rock structure).
Definition
sill
Term
_____ rocks have coarse crystals in a fine-grained matrix.
Definition
Porphyritic
Term
Both andesite and ___ are composed of feldspars and 30% to 50% ferromagnesian minerals
Definition
diorite
Term
___ are igneous rocks that are silica-deficient but high in iron and magnesium.
Definition
mafic
Term
Igneous rocks that are silica-rich with high aluminum, sodium, and potassium are _____ rocks.
Definition
silicic
Term
A ______ is an intrusive structure that formed from magma that solidified within the "throat" of a volcano.
Definition
volcanic neck
Term
The most common minerals in a granite are the ______.
Definition
feldspars
Term
______ is the predominant igneous rock of the continents.
Definition
Granite
Term
The melting point of a mineral generally _____ with increasing pressure (or depth).
Definition
increases
Term
Hawaii and __________ eruptions are related to intraplate igneous activity
Definition
yellowstone
Term
On its slow journey through the crust, mafic magma evolves into intermediate magma by differentiation and assimilation of ______.
Definition
silicic rocks
Term
Most of the basalt and gabbro on the ocean floor is created at mid oceanic ridges, which are also ____.
Definition
divergent plate boundaries
Term
The crust beneath the world's oceans is mafic ________.
Definition
bassalt and gabbro
Term
How is a sill different from a dike?
Definition
Sills are parallel to the layering in the country rock.
Term
The coarse-grained equivalent of basalt is a(n) ______.
Definition
gabbro
Term
What type of melting takes place when a body of hot mantle rock moves upward and the pressure is reduced to the extent that the melting point drops to the temperature of the body?
Definition
decompression melting
Term
What is the sequence of crystallization along the discontinuous branch of Bowen's reaction series?
Definition
olivine, pyroxene, amphibole, mica
Term
Viscosity is a property of a fluid that relates to how easily the fluid flows. A material that is viscous __.
Definition
flows less easily
Term
Imagine two magmas that are identical in all respects (for example, same chemistry, pressure, volume) except that one magma is hotter than the other. Which magma will have the higher viscosity?
Definition
The cooler magma will be more viscous.
Term
What is the process through which magma differentiation takes place?
Definition
crystal settling
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