What type of mountains are the Cascades in Northern CA, OR, WA and Canada? How did they form?
The mountains of the Cascades are a folded mountain belt. They are the result of the collision between the North American plate and the Juan de Fuca plate. These are two lithospheric plates. As they collide, the stress of their collision is causing the western edge of North America to fold and buckle. Additionally, the Juan de Fuca plate is being shoved down into the mantle beneath North America. As it gets forced deeper into the mantle, water in the plate facilitates the melting of the rocks of the plate and overlying mantle. The molten rock thus created (magma) rises upward eventually generating volcanism on the surface. So, it is these two processes, folding and volcanism, that have built up the Cascade Mountains.
