What happens when molten material travels along the underside of the crust?

Explanation:

The earth is comprised of denser materials such as iron and nickel and other siderophile elements in the core and silicate materials in the mantle. The temperature at the core of the earth is extremely high that generates a force, that allows the molten materials (magma) to rise up from the bottom of the mantle towards the crust, in the form of convection currents. This upward movement of magma forces the lithospheric plates to move.

Thus, magma rises from the bottom of the mantle towards the crust.