Very hot magma rises toward the surface because it is less dense. The magma
becomes
as it cools, and
back toward the
core

form in the mantle where hot magma keeps rising.
then cools and sinks again

The movement of magma under the crust applies
plates
to tectonic plates

Rising hot magma pushes up on the crust, causing it to break and allowing
to form
happens where magma moving sideways and lava
forming new crust pushes plates in opposite directions.

Oceanic trenches form where denser oceanic crust is pushed under lighter
crust. The subducted plate begins to melt as it moves
into the mantie