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Introduction to Geology
Volcanic Stones
The Origins of Magma and
Igneous Rocks
The Rock Cycle
The Formation of Igneous Rocks
Eruption as lava or ash
Forms magma chamber (solidifies or rises)
Accumulates into rising magma body
Partial melting of source
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The Origins of Magma
The four main factors that influence the origins of magma are:
* Temperature
* Water Content
* Pressure
* Mineral Composition
Geologic Settings in which Magma Originates
Magma Formation and the Geothermal Gradient
The Formation of Magma
The Formation of Magma
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The Formation of Magma
Solid
Pressure tends
to hold lattice
together
Liquid
Increasing temperate vibrates
atoms and can break bonds
Melting Rocks
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The Formation of Magma
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Solid asthenosphere
rises to fill gap
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Decompression
melting
The Formation of Magma
Pillow basalt
Sheeted dikes
of basalt
Gabbro
Mantle
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The Formation of Magma
Crustal Heating
Decompression
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The Formation of Magma
Few volcanoes
Felsic rocks
(granite)
Burial and heating
of crustal rocks
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Melting during
subduction before
collision (but shuts off)
The Formation of Magma
Oceanic island
Rising
mantle
plume
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Crustal
melting
and caldera
in continent
Huge
basalt
flows on
continents
The Formation of Magma
Mostly felsic and
intermediate rocks
Mafic magma
melts crust
Adding water
melts mantle
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The Formation of Magma
Mostly mafic and
intermediate
rocks
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Add water to
hot mantle
The Formation of Magma
Hot water circulates in ridge; added in
pores and in minerals
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Water in minerals released at depth
Mantle Melting and Plate Tectonics
The Formation of Magma
The Formation of Magma
Observe these settings where large magma chambers form, and propose
causes of melting for each site
Mid-ocean ridge
Oceanic hot spot
Subduction beneath
continent
Continental
collision
Continental hot spot
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This Concludes
Volcanic Stones
The Origins of Magma and
Igneous Rocks