The lighter plates rests on top


Source: Wikipedia Commons
Source: Wikipedia Commons

The lighter plates rests on top

The earths continents are a result of the lighter masses originally resting closer to the center, shifted and moved up early in the history of the planet. We know that the continental plates are significantly lighter than the heavier ocean plates. This is due to the fact that tightness of the masses increases as we get closer to the center of the earth.  

The ocean plates melts and creates mountain formations

As a result of the ocean plates spreading, the heavier plates resting on the bottom of the sea gets pushed under the lighter continental plates. This results in the ocean plates melting and is pushed to the surface, creating mountain chains and mountain formations.  

Source: Geology.com
Source: Geology.com

Wegeners model

The continental plates and the ocean plates are measured to be around 100 to 200 km thick, and forms the outer "shell" (Lithosphere) covering the earth. As for the Lithospheric plates, they are covering the layer underneath, called the Asthenosphere. The earth isn't, as most people tend to believe, completely rounded. The earth`s natural form is that its pushed down at the poles and bulges out around equator.