Question

Explain where the magma for volcanoes at divergent plate boundaries comes from and how it rises to the surface. In this explanation describe how mantle convection is related to the motion of the tectonic plates.

Answer 1

The earth's crust is comprised of lithospheric plates and they are divided into the continental crust (plates) and the oceanic crust (plates). These plates are constantly in motion over the Asthenosphere layer. This motion takes place due to the convection current that initiates in the mantle. This initiation of convection current is because of the heat radiated from the core of the earth. This plate motion takes place in three different ways, such as-

(a) Divergent plate motion

(b) Convergent plate motion

(c) Transform plate motion

In a divergent plate motion, the two plates move in the opposite direction. As a result of which the hot, less dense magma rises up and comes out towards the surface. This magma originates from the deeper mantle due to the convection current.

Hence, the convection current is the main mechanism behind the plate motion.