There are two types of crusts - the continental and the oceanic. The continental crust is

There are two types of crusts - the continental and the oceanic. The continental crust is thicker below the mountains than below the plains. Both continental and oceanic crusts are less dense than the mantle, so both float in the mantle. Continental crust floats higher in the mantle than oceanic crust because continental crust is both less dense and thicker than oceanic crust.