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The distribution of volcanoes
Transcript of The distribution of volcanoes
Magma is created by the melting of rock . . . any rock.
But, volcanoes do not occur everywhere . .
They occur in specific tectonic settings.
Over hotspots hot rock deep in the mantle rises to areas of lower pressure where it expands and melts.
Up-welling and thinning of the lithosphere causes melting along divergent boundaries.
Something has to happen to cause rocks to melt.
Melting occurs when the pressure on hot rocks is reduced.
Water is a flux--it reduces the melting temperature of hot rocks.
This is the principle cause of melting along subduction zones.
Melting of continental crust will occur if mafic magma pools at its base.
Felsic sediments with low melting temperatures will melt if transported into the mantle along a subduction zone
In summary, melting occurs where:
1. pressure is reduced
2. water is released into hot rocks
3. felsic rocks are dragged into regions of
high temperature, and
4. where mafic magma pools at the
base of the continent
These processes are all related to
Water can also
cause hot rocks to