| The crust is composed of two basic rock types
granite and basalt. The continental crust is composed mostly of granite. The oceanic crust
consists of a volcanic lava rock called basalt. Basaltic rocks of the
ocean plates are much denser and heavier than the granitic rock of the
continental plates. Because of this the continents ride on the denser
oceanic plates. The crust and the upper layer of the mantle together
make up a zone of rigid, brittle rock called the Lithosphere. The layer
below the rigid lithosphere is a zone of asphalt-like consistancy called
the Asthenosphere. The asthenosphere is the part of the mantle that
flows and moves the plates of the Earth.
Click on the "Next" button to learn more!