Exam 2 part 1 Flashcards
Study for exam 2.
What are Felsic and Mafic rocks and what do the terms mean?
Igneous Rocks, Felsic and Mafic are terms to describe what they are made of
What does felsic and mafic mean in terms of composition?
It means that felsic rocks have more silica in them while mafic rocks do not.
What influences Magma behavior?
Silica content
Generally, what silica content does Granitic Magma have and what consistency does it have?
It generally has a high silica content and it’s consistency is also viscous, meaning it has high resistance to internal flow
Generally, what silica content does Basaltic Magma have and what consistency does it have?
It generally has a low silica content and it’s consistency isn’t viscous, meaning it has low resistance to internal flow
What does intermediate mean for felsic and mafic rocks?
It means that it’s in the middle between felsic and mafic rocks in terms of it’s silica content.
What kind of rock is Phaneritic and where can you find it?
It’s a coarse grained igneous rock and you can find it from cooled magma underground
What kind of rock is Aphantitic and where can you find it?
It’s a fine grained igneous rock and you can find it from cooled magma above around.
What is the name of a Felsic Phaneritic rock?
Granite
What is the name of a Felsic Aphanitic
Rhyolite
What are Obsidian and Pumice and what is the difference between them?
They are both igneous rocks with glassy texture, but obsidian is compact and dark in color while Pumice is frothy and light in color
What are Andesite and Diorite and what is the difference between them?
They are both igneous rocks but Andesite has a volcanic origin and is fine grained and Diorite has a Plutonic origin and is coarse grained
What is Basalt and what is it made of?
Volcanic igneous rock with a amphanic texture. Made of calcium-rich plagioclase feldspar and pyroxene.
What is the most common extrusive igneous rock?
Basalt
What is Gabbo and what is an equivalent of?
Plutonic igneous rock with a Phanetitic texture. Equivelant of Basalt meaning it’s also made of calcium rich plagioclase feldspar and pyroxene
Which rock is a significant percent of the ocean floor?
Gabbo
What are pyroclastic rocks?
Fragments ejected during a volcanic eruption
What is tuff?
Ash-sized fragments
What is Volcanic Breccia?
Fragments bigger than ash
What is tuff made of?
It can be made of anything that’s in the lava flow. Tuff is just a fragment size
How does heat work in the crust?
It gets warmer, 20 celcius to 30 celcius per kilometer
If rocks are near their melting point, where are they usually?
In the lower crust and upper mantle
When you have a lot of pressure on a rock what does it do?
It increases the rock’s melting point in temperature
What happens if you decrease the pressure of a rock that has had a lot of pressure on it?
It will melt because of decompression melting
Where does decompression melting occur?
It occurs in the asthenosphere
What are volatiles?
They are primarily water.
What do volatiles do?
They cause rocks to melt at a lower temperature
How do minerals crystallize?
they crystallize in systematic fashion based on their melting points
Does anything change in magma when it crystallizes?
Yes, the composition of the liquid portion of magma makes continuous changes through out crystallization
What are the 3 processes that can change a magma’s composition?
1) Magmatic Differentiation
2) Assimilation
3) Magma mixing
What is Magmatic Differentiation?
This is what crystal settling is. Where earlier formed crystals in the magma settle at the bottom of the chamber because they are heavier.
What is Assimilation?
A change in the magma’s composition by adding some of the rock that surrounds the magma.
What is magma mixing?
When two chemically distinct magmas produce a composition quite different from either original magma
What is partial melting
It’s when the melting of rocks is incomplete
Where do most basaltic magma originate from?
Most originate from the partial melting of ultra mafic rock in the mantle at oceanic ridges
What kind of magma is common at the Earth’s surface?
Large out pourings of basaltic magma is common at the Earth’s surface
What are the 2 ways that Andestic magma is formed?
1) It’s produced by the interaction of basaltic magma and silica-rich rock in the crust.
2) Magmatic Differentiation
How is granitic magma formed?
They form as the end product of crystallizations of andesitic magma.
Which magma is the most viscous? Can this magma reach the surface?
Granitic magma, they tend to lose their mobility before reaching the surface.
What kind of structures do granitic magma produce?
They tend to produce large plutonic structures.
