cascadia event

The Cascadia subduction zone (also referred to as the Cascadia fault) is a convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long, sloping subduction zone that separates the Explorer, Juan de Fuca, and Gorda plates, on the one hand, and the North American Plate, on the other.
The denser oceanic plate is subducting beneath the less dense continental plate offshore of British Columbia, Washington, Oregon, and northern California. The North American Plate is moving in a southwest direction, overriding the oceanic plate. The Cascadia subduction zone is where the two plates meet.
Tectonic processes active in the Cascadia subduction zone region include accretion, subduction, deep earthquakes, and active volcanism of the Cascades. This volcanism has included such notable eruptions as Mount Mazama (Crater Lake) about 7,500 years ago, Mount Meager about 2,350 years ago, and Mount St. Helens in 1980. Major cities affected by a disturbance in this subduction zone include Vancouver and Victoria, British Columbia; Seattle, Washington; and Portland, Oregon.

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