Week 5 - Convergent Plates that Formed the Cascade Range

This week I visited the Cascade Range in Northern America, which extends from South Western Canada through the North Western US into California. The mountains are formed by the converging force of the Pacific and North American plates. The stress produced by the subduction of the Pacific plate compresses the North American plate side and uplifts the area into the mountain ranges that are present now.

Source: https://www.bpa.gov/news/newsroom/Pages/BPAs-participation-in-Cascadia-Rising-exercise-featured-in-NWPPA-Bulletin.aspx

As is typical of dip-slip faults, the friction and resulting heat create volcanoes that form in a parallel line to the fault. The Cascade Range is home to several well-known volcanoes, such as Mount St. Helena, Mount Rainier and several others. These fault lines are reverse or thrust faults, since the stress is a compression force. Faults are the dominant stress feature across the Range.

Source: https://volcanoes.usgs.gov/observatories/cvo/cascade_volcanoes.html

Along the mountain range, new rock is being formed through volcanic activity. This igneous rock is deposited by volcanoes and vents, which then cools to harden and form new rocks. The subduction activity also acts to uplift the Cascade Range, slowly raising it from the surrounding plate. Nearer to the fault line, the action of the subducting Pacific plate sliding under the North American plate deposits rock along the fault, called the accretionary wedge. This formed the Upper Western US and is composed of rock that once composed the bottom of the Pacific Ocean.