Question

What provides the mechanism by which mantle rocks melt and magma is produced?

Answer 1

Decompression

Explanation:

At mid-ocean ridges, decompression melting is the major mechanism by which mantle rock is melted and ultimately turned into oceanic crust.

Decompression melting is when we bring rocks up from high pressure to low pressure with little heat exchange. Objects that travel along a path with no heat exchange with the surroundings are said to be adiabatic.

So the mantle is brought up along an adiabatic path and then melts upon decompression, then we get magma!