How are they formed?

What are they?

An actively deforming region

*outermost shell of a rocky planet

where two (or more) tectonic plates or fragments of lithosphere* move toward one another and collide

Oceanic-continental

Oceanic-oceanic

If one crust is denser than the other

The denser Crust is forced under the less dense crust ,into the mantle

Process is called subduction and the area it takes place is called the subduction zone

Oceanic plate pushes into and subducts under a continental plate

Overriding continental plate is lifted up and a mountain range is created