Notice the line of volcanoes that form the Cascade Range, extending from northern California to southern Canada. These are active volcanoes, meaning that they still erupt from time to time. What sequence of plate tectonic events is causing these volcanoes to form

Colliding plates (slab pull)

Explanation:

Volcanoes are formed when tectonic plates collide with one another and one plate is pushed beneath another, they can also be formed when move away from each other. this give rise to hot magma rising from the earth upper mantle crust to the surface.

Cascade range volcanoes consist of a oceanic plate sub-ducting beneath a continental plate and they are still active and erupting from time to time due to colliding plate, the major driving force for it movement is a slab pull