Why is there melting and volcanism at subduction zones?

It’s relatively cold!

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Hydrous minerals warm up and dehydrate.

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• Hydration of oceanic floor at MOR• More and deeper hydration due to outer

rise faults (bending at trench)• Dehydration of hydrous minerals• Fluid moves up into warmer mantle

which melts.

Melting at subduction zones

Why are there deep Earthquakes?

• Normal stress across any fault plane is so high that you would need enormous stresses to cause it to move (i.e. high frictional strength.

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Negative volume change reduces friction

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