Earth Sciences 1022A/B Chapter Notes - Chapter 3: Magma Chamber, Igneous Rock, Geothermal Gradient

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Published on 22 Sep 2012
Department
Igneous Rocks 9/18/2012 9:17:00 AM
- Ignis “fire”
- Form from molten material magma (less dense than rocks)
magma is formed through process partial melting
o occurs at various levels of crust and upper mantle
magma that reaches earth’s surface = lava, melted portion = melt, solid =
silicate minerals
forms at surface
o extrusive / volcanic
sometimes loses mobility before reaching surface, igneous rock forms at
depth
o intrusive / plutonic
o occurs in BC
primary magma
o from direct melting of rocks, has not evolved yet
secondary magma
o changed and evolved
Generating Magma from Solid Rock
HEAT
- Geothermal gradient, hotter deep in the earth
Pressure also increases with depth
PRESSURE
Increase in confining pressure causes rise in rock’s melting temperature
Decompression melting is triggered where confining pressure drops
When rock goes up from convective upwelling, moves into zones of lower
pressure, thus melts generates magma along ocean ridges where plates are
drifting apart
VOLATILES
rock’s water content can affect rock to melt at lower temperatures
wet rock has lower melting temp than dry
- Magma due to lighter density, rises through volcano
- Volcanoes came from ancient god of fire, Volcan
Figure 1
- Pattern occurs called “texture”
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Document Summary

Form from molten material magma (less dense than rocks) Magma is formed through process partial melting: occurs at various levels of crust and upper mantle. Magma that reaches earth"s surface = lava, melted portion = melt, solid = silicate minerals forms at surface: extrusive / volcanic. Sometimes loses mobility before reaching surface, igneous rock forms at depth intrusive / plutonic: occurs in bc. Primary magma: from direct melting of rocks, has not evolved yet. Geothermal gradient, hotter deep in the earth. Increase in confining pressure causes rise in rock"s melting temperature. Decompression melting is triggered where confining pressure drops. When rock goes up from convective upwelling, moves into zones of lower pressure, thus melts generates magma along ocean ridges where plates are drifting apart. Volatiles rock"s water content can affect rock to melt at lower temperatures. Wet rock has lower melting temp than dry. Magma due to lighter density, rises through volcano. Volcanoes came from ancient god of fire, volcan.

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