Question

Rocks can melt without changing temperature when the pressure exerted on them is

Answer 1

By low temperature, it can melt. High pressure will raise the  melting point of the rock.  

Answer 2

The answer is "decreased". Theoretically speaking this is called decompression melting, It is the reduction in pressure which enables the rock to melt, leading to magma foundation.

Step-by-step explanation:

It is known that a rapid decrease in pressure can cause the mantle to melt, even without an increase in temperature. This is called decompression melting.