Mountains

The thicker parts of the continents float higher than the thinner parts, and any process that thickens the continental crust will bring about the uplift of the thickened portion. Continental crust "floats" in the mantle, and can be compared to the way an ice cube floats in water. An ice cube floats because it is lighter per unit volume than water—that is, ice is less dense than liquid water. The ice cube may weigh a few ounces, and rise a centimeter above the water's surface. An iceberg might weigh millions of tons, but float a hundred feet out of the water, because although it is vastly heavier than the ice cube, it is still less dense than water per unit volume—it floats. The more there is of it, the higher it floats. Similarly, any mass of continental crust, no matter how thick, is still less dense per unit volume than the mantle rock beneath it. Thus the edge of the continent begins rising to a higher elevation, and mountains begin to form.

Mountains are generated both at the edges of plates, and within plates. Other processes, such as sedimentation and erosion, modify the shape of the land that has been forged by plate tectonics.