Volcanoes of the Northern Oregon Cascade Range

January 26, 2023


Photographer: Marli Miller   
Summary Author: Marli Miller 

The Cascade Volcanoes form a linear chain that runs north-south from northern California to southern British Columbia. They form a line because they’re fed by magma that originates by subduction of the Juan de Fuca Plate beneath North America -- and the subduction zone trends north-south (see schematic figures below).

This photo shows part of the volcanic chain, from South Sister northward to Mts Jefferson and Hood; Mt. Adams in Washington appears faintly on the horizon. Two rhyolitic lava flows, erupted between 2000-2300 years ago, appear on the flanks of South Sister. Notice also the many smaller peaks and cones. The Oregon Cascades hosts more than a thousand volcanic vents that have erupted in the last 2 million years. These vents are mostly basaltic in composition but include andesitic and rhyolitic ones as well. Photo taken on December 16, 2022.

Oregon’s Cascade Range Coordinates: ~44.000, -121.900

Related Links:

Cascades Volcanoes in Oregon

Marli’s Website

Quaternary Magmatism in the Cascades 

Roadside Geology of Oregon