How would you describe the motion of plates in a collision zone?

The plates move INTO each other in a convergent boundary causing a collision. As the plates collide, the denser plate becomes subducted under the less dense plate. There is enormous stress between the two plates as they move past each other. This stress from the friction causes the plates to warp at the boundary. The geographical feature formed at such a boundary is the mid-ocean trench - along the boundary.