Here's why:

* Active margins occur where an oceanic plate collides with a continental plate. This collision leads to:

* Subduction: The denser oceanic plate sinks beneath the continental plate.

* Volcanic activity: Magma rises from the subducting plate, creating volcanoes.

* Earthquakes: The collision and movement along the fault zone cause frequent earthquakes.

* Mountain ranges: The collision forces the continental plate to buckle and uplift, creating mountains.

The Pacific coast of North America exhibits all these characteristics. The Juan de Fuca Plate is subducting under the North American Plate, causing the Cascade Range volcanoes, frequent earthquakes, and the formation of the Coast Mountains.