Basalt
Basalt is the most common extrusive
rock on earth. It is mostly extruded as lava flows.
There are 4 types of Basalt according
to thier zone of formation.
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Ocean Floor
Basalt
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Magma is produced by plate spreading
resulting in adiabatic decompression melting of the peridotite mantle. |
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Ocean Island
Basalt
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These basalts are caused by adiabatic
decompression of mantle plumes. They are oceanic hot spot volcanoes.
Examples are: Hawaii, Azore, Canary
Islands, Easter Island, Reunion. |
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Island
Arc Basalt
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These basalts are formed above subduction
zones by decompression melting of the mantle due to the addition of volatiles.
Examples: Ambrym, Lopevi, Tinakula. |
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Continental
Basalt
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These are formed in Rift Valleys
by adiabatic melting within mantle plumes due to plate spreading.
Examples: East African Rift Valley,
Baikal Rift (Siberia), Rio Grande Rift (USA). |
    
Basalt
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Copyright John Seach
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