Cascade Volcanoes

The Cascade Volcanoes are a chain of volcanoes in western North America, formed as the Juan de Fuca Plate and related oceanic plates descend beneath the North American Plate.

Cascadia Subduction Zone: A convergent plate boundary where the Juan de Fuca Plate and related plates descend beneath North America. This plate boundary supplies the tectonic setting and water-rich mantle melting behind the Cascade arc.
Mount St. Helens: An active stratovolcano in Washington known for its catastrophic 1980 eruption. Its 1980 eruption illustrates how explosive activity can reshape a Cascade volcano and its surroundings.
Volcanic hazard: A threat to people or infrastructure caused by volcanic activity or its associated processes. Cascade hazards include ashfall, lava, pyroclastic flows, lahars, and volcanic gases.
Juan de Fuca Ridge: An underwater spreading ridge where new oceanic crust forms off the Pacific Northwest. Crust produced here travels eastward before joining the subduction system beneath the Cascades.
Juan de Fuca Plate: A small oceanic tectonic plate that is subducting beneath western North America. Its descent drives much of the volcanism in the northern and central Cascades.
Mount Rainier: A heavily glaciated active stratovolcano in Washington and the highest peak in the Cascade Range. Its glaciers and nearby population make volcanic lahars a major regional hazard.
Lahar: A fast-moving mixture of water, volcanic debris, and sediment flowing down a volcano's slopes or valleys. Rain and melting ice can turn Cascade volcanic debris into destructive valley-filling flows.
Farallon Plate: An ancient oceanic plate that was largely consumed by subduction beneath western North America. Its remnants and earlier subduction shaped the tectonic history that preceded the modern Cascade arc.
Volcanic arc: A curved chain of volcanoes that forms above a subduction zone. The Cascades are a continental example of this global volcanic pattern.
Mount Hood: A potentially active stratovolcano in northern Oregon and the state's highest mountain. It is a prominent southern Washington–Oregon segment of the chain, with glaciers and persistent unrest.

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