The outer layer of the earth, the crust, is not a solid, unbroken layer but is actually cracked like the shell of an egg. The crust is divided into tectonic plates:
Continental and Oceanic Crust
As we now know the earth’s crust is divided up into a series of plates. Some of these plates are above sea level (known as continental crust) and some of these plates are below sea-level (known as oceanic crust).
There are some extremely important differences between them: