GEOG 150 Lecture Notes - Lecture 3: Metamorphic Rock, Igneous Rock, Continental Crust
Igneous rocks
Formed when magma cools and hardens
Sedimentary rocks
Formed when sediment gradually accumulates in layers and over a long period of time hardens into
rocks
Metamorphic rocks
Formed when pre-existing rock is subjected to intense heat and pressure which cause physical and/or
chemical changes
The rock cycle
Magma COOLS AND HARDENS-> IGNEOUS ROCK
Igneous rock, sedimentary rock, or metamorphic rock WEATHERS-> SEDIMENT
Sediment is cemented/compacted/ LITHIFIED-> SEDIMENTARY ROCK
Igneous rock or sedimentary rock are subjected to intense heat and pressure/ METAMORPHISM->
METAMORPHIC ROCK
Metamorphic rock or rock in mantle MELTS-> MAGMA
Magma
Created by the melting of rocks
General characteristics of magma
parent material of igneous rocks
formed by partial melting of Earth's crust
magma at surface is called lava
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The three components of magma
melt (liquid)
crystals of silicate materials (solid)
volatiles (gas)
Melt
Liquid component of magma that is composed of mobile ions of the eight most common elements in
Earth's crust
Volatiles
The gaseous component of Earth's crust which are dissolved gases in the melt that vaporize at surface
pressure
Three most common volatiles in magma
Water vapor
Carbon Dioxide
Sulfur Dioxide
Geothermal gradient
The rate of increasing temperature in respect to increasing depth in the Earth's interior
Source of magma
The Earth's crust and mantle
Three conditions in which magma forms
Decompression melting
Heat transfer
Addition of water
Decompression melting
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Occurs when confining pressure drops significantly, by hot, solid mantle rock ascending in zones of
convection upwelling, thus moving into regions of lower pressure.
Where does decompression melting occur
At divergent plate boundaries. The hot mantle rises and melts, replacing the material that has shifted
horizontally away.
Heat transfer
When magmas rise towards the surface, intruding into the cold crust, and upon solidification they lose
their heat and transfer it to the surrounding crust.
Where does heat transfer occur?
Continental rift valleys, hot spots, and subduction related environments.
Addition of water
Water and other volatiles act as salt does to ice, so water causes rock to melt at lower temperatures;
When cool slabs of oceanic lithosphere descend into the mantle, heat and pressure drive water from the
subducting oceanic crust into the hot mantle, generating magma.
Where does the addition of water occur?
Occurs mainly at convergent plate boundaries
Types of magma
Mafic/Basaltic
Intermediate/Andesitic
Felsic/Granitic
Felsic/Granitic
composition
minerals
high silica content
high viscosity
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Document Summary
Formed when sediment gradually accumulates in layers and over a long period of time hardens into rocks. Formed when pre-existing rock is subjected to intense heat and pressure which cause physical and/or chemical changes. Igneous rock, sedimentary rock, or metamorphic rock weathers-> sediment. Igneous rock or sedimentary rock are subjected to intense heat and pressure/ metamorphism-> Metamorphic rock or rock in mantle melts-> magma. General characteristics of magma parent material of igneous rocks formed by partial melting of earth"s crust magma at surface is called lava. The three components of magma melt (liquid) crystals of silicate materials (solid) volatiles (gas) Liquid component of magma that is composed of mobile ions of the eight most common elements in. The gaseous component of earth"s crust which are dissolved gases in the melt that vaporize at surface pressure. The rate of increasing temperature in respect to increasing depth in the earth"s interior.
