Final answer:
The Cascade Mountain Range was formed primarily by the modern subduction of the Juan de Fuca and Gorda Plates under the North American Plate, resulting in an active volcanic range.
Step-by-step explanation:
Part of the process of the formation of the Cascade Mountain Range involves the subduction of the Juan de Fuca and Gorda Plates beneath the North American Plate. Unlike the Sierra Nevada range, which exposes the eroded core of ancient volcanoes, the Cascade Range is modern and active.
This subduction zone is responsible for the range's numerous volcanoes, including prominent peaks like Mount Rainier and Mount Saint Helens.