Why does magma in the mantle rise to the crust above it?

The magma rises to the crust above it mostly because of the cracks that appear in the crust and the high pressure from the mantle that pushes the magma through these cracks. The cracks in the crust appear because of the tectonic activities, on and in close proximity to the plate boundaries. This is why the volcanic activities, a product of rising magma, are found along the plate boundaries. The magma can rich the crust and solidify in it, or it can come out on the surface in the form of lava flows. The one that solidifies inside the crust forms the intrusive igneous rocks, while the one that comes on the surface forms the extrusive igneous rocks. The rocks formed from the magma are the basis for the formation of the other rock types, as well as for the formation of land masses, and soils.