Convection Currents:a current in a fluid that results from convection.
Oceanic Crust: the relatively thin part of the earth's crust that underlies the ocean basins. It is geologically young compared with the continental crust and consists of basaltic rock overlain by sediments.
Continental Crust:the relatively thick part of the earth's crust that forms the large landmasses. It is generally older and more complex than the oceanic crust.