Igneous rocks hw
How do the crystallization and settling of the earliest formed minerals affect the composition of the remaining magma?
After the earliest formed minerals have settled, the resulting magma will be more felsic than the original magma
What is the rock name of an intermediate rock with two distinct grain sizes?
Andesite porphyry
What is required to generate an igneous rock with a fine-grained texture?
A fine-grained texture is the product of rapid cooling and crystallization of lava.
What is an accessory mineral?
A mineral that makes up a relatively small portion of the total rock composition
How is basaltic magma transformed into felsic magma?
Basaltic magma partially melts the continental crust, which is more felsic in composition.
Why does partial melting result in a magma having a composition different from the rock which it was derived?
Because different minerals melt at different temps., minerals that melt at lower temps will melt from the rock first, creating a magma formed from the minerals that melted first
Pyroclastic debris from a volcanic eruption can include _____.
ash and cinders
What is the term used to describe a very large, widespread, and deep intrusive body of igneous rock?
batholith
Which of the following terms is the best described as a massive pluton?
batholith
A phaneritic texture is characteristic of a(n) ______ igneous rock that cooled ________.
intrusive; below the surface
Why does magma have a tendency to rise after its formation?
it is less dense than the surrounding rock
What is one way a glassy texture forms?
lava cools rapidly
As a result of partial melting, magma originates in __________.
mantle and crust
Ultramafic rocks contain __________ and are commonly found in __________.
olivine; mantle
What do pumice and scoria have in common?
They both exhibit a vesicular texture.
Most igneous rocks never reach the surface. However, igneous rocks other than those formed in volcanoes are found exposed on many parts of Earth. How do you account for this phenomenon?
They formed at depth and have been exposed by uplift and erosion.
At a subduction zone melting is triggered by _____
the introduction of water
How do light-colored igneous rocks differ from dark-colored igneous rocks?
Dark colored igneous rocks have a higher iron and magnesium content than light colored rocks
What causes an elevated geothermal gradient in a divergent plate setting?
Decompression melting of the mantle
What is the term for a tabular igneous pluton that occurs in an orientation that is discordant with the bedding surfaces of adjacent sedimentary rocks?
Dike
What is the difference between extensive igneous rocks and intrusive igneous rocks?
Extrusive igneous rocks cool and solidify on the Earth's surface, whereas intrusive igneous rocks cool and solidify beneath the Earth's surface
Once a source partially melts, what does it produce?
Felsic magma and mafic residue
You have found a mafic rock with a phaneritic texture. What is a potential rock name?
Gabbro
Which of the following best describes the difference between granite and rhyolite?
Granite is phaneritic and rhyolite is aphanitic.
Which of the following choices below lists the four basic compositional groups of igneous rocks, ranging from the highest silica content to the lowest silica content?
Granite, andesitic, basalt, ultramafic
Igneous rocks of felsic composition have ____ and ____ relative to magic igneous rocks.
Greater silica; lower melting temperature
Intrusive and extrusive igneous rocks are classified based on what criteria?
How quickly the molten rock cools and crystallizes, and where this occurs with respect to Earth's surface.
How are igneous rocks formed?
Igneous rocks are formed by the cooling and crystallization of molten rock.
Which of the following is true about magic igneous rocks?
Mafic igneous rocks are rich in Fe, Mg, and Ca
Based on the diagram shown in the video, name two minerals that are unlikely to coexist in the same igneous rock?
Muscovite and Pyroxene
Which of the following igneous rocks contains no mineral crystals?
Obsidian
Which of the following textures describe an igneous rocks with anomalously large crystals?
Pegmatitic
Fill in the blanks using the choices below:___are minerals typically found in igneous rocks that have high silica content, whereas____ are minerals that are typically found in igneous rocks with a low silica content.
Plagioclase feldspar and quartz; pyroxene and olivine
Which of these crystals would be the first to crystallize in a body of magma?
Pyroxene
According to Bowen's reaction series, ____ is one of the first minerals to melt, but last to crystallize.
Quartz
Based on what you learned in this video, what minerals make up rhylolite?
Quartz, K-feldspar, and plagioclase feldspars, with relatively fewer biotite and amphiboles
What is the term for a tabular igneous pluton that occurs in an orientation that is concordant with the bedding surfaces of adjacent sedimentary rocks?
Sill
What is the geothermal gradient, and how does it relate to the melting curve of peridotite?
The geothermal gradient is the increase in temperature with depth under the Earth's surface. The melting curve of peridotite is consistently higher than the geothermal gradient.
What does it mean if an igneous rock has an an aphanitic texture?
The igneous rock exhibits mineral crystals too small to see with the naked eye
In a subduction zone, water driven from subduction oceanic crust causes
The melting temperature of mantle rocks to decrease
What does an igneous rock with a pyroclastic texture tell a geologist?
The rock was likely formed by a violent volcanic eruption
In what type of igneous feature would you find rocks with a vesicular texture?
The surface of a lava flow
How does decompression melting occur?
When hot, solid mantle rock ascends, it moves to areas of lower pressure. This reduction in pressure allows the hot material to melt into a less compressed liquid phase.
When lava erupts at Earth's surface, what type of rock is produced?
extrusive
Working in the field, you see a thin, dark-colored igneous sill across the valley. Without seeing the sill up close, what texture would you expect it to possess?
fine grained
Which of the following textures indicates two stages of cooling and crystallization?
porphyritic
Which of the following describes a texture containing bubble-shaped cavities
vesicular
