Relate density and crustal thickness to mountain buildings?

The process of mountain building is called orogeny. Mountains are usually formed on continental crust. Continental crust is buoyant and less dense than oceanic crust. When these plates interact the less dense continental plate will override the more dense oceanic plate which will subduct. The resulting compression created by the interaction of the plates cause folding leading to the creation of fold mountain ranges. Fold mountain ranges are the thickest sections of the earth's crust. 

Answerseafloor spreading;

Adrought is taking place