Editing Cascadia subduction zone (section)

{{Short description|Convergent plate boundary that stretches from northern Vancouver Island to Northern California}}
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| image2            = 9.0 Cascadia scenario (median).pdf
| footer            = Area of the Cascadia subduction zone (left) and a USGS scenario ShakeMap for a Mw9.0 event
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The '''Cascadia subduction zone'''  is a {{cvt|960|km}} [[convergent boundary|convergent]] [[plate boundary]], about {{cvt|70|-|100|mi|-2|order=flip}} off the Pacific coast of North America, that stretches from northern [[Vancouver Island]] in [[Canada]] to [[Northern California]] in the United States.  It is capable of producing 9.0+ [[Moment magnitude scale|magnitude]] earthquakes and [[tsunami]]s that could reach 30&nbsp;m (100&nbsp;ft) high. The Oregon Department of Emergency Management estimates shaking would last 5–7 minutes along the coast, with strength and intensity decreasing further from the epicenter.<ref>{{cite web | url=https://www.oregon.gov/oem/hazardsprep/pages/cascadia-subduction-zone.aspx | title=Oregon Department of Emergency Management : Cascadia Subduction Zone : Hazards and Preparedness : State of Oregon }}</ref> It is a very long, sloping [[subduction]] zone where the [[Explorer plate|Explorer]], [[Juan de Fuca plate|Juan de Fuca]], and [[Gorda plate|Gorda]] plates move to the east and slide below the much larger mostly continental [[North American plate]]. The zone varies in width and lies offshore beginning near [[Cape Mendocino]], Northern California, passing through [[Oregon]] and [[Washington (state)|Washington]], and terminating in Canada at about [[Vancouver Island]] in [[British Columbia]].<ref name="Schulz2015" />

The Explorer, Juan de Fuca, and Gorda plates are some of the remnants of the vast ancient [[Farallon plate]] which is now mostly subducted under the North American plate. The North American plate itself is moving slowly in a generally southwest direction, sliding over the smaller plates as well as the huge oceanic [[Pacific plate]] (which is moving in a northwest direction) in other locations such as the [[San Andreas Fault]] in central and southern California.

Tectonic processes active in the Cascadia subduction zone region include [[Accretion (geology)|accretion]], [[subduction]], deep [[earthquake]]s, and active [[volcanism]] of the [[Cascade Volcanoes|Cascades]]. This volcanism has included such notable eruptions as [[Mount Mazama]] ([[Crater Lake]]) about 7,500 years ago, the [[Mount Meager massif]] ([[Bridge River Vent]]) about 2,350 years ago, and [[Mount St. Helens]] in 1980.<ref name="emporia.edu">{{cite web|url=http://www.emporia.edu/earthsci/student/geller2/cascadia.html |title=Cascadia Subduction Zone Volcanism in British Columbia |access-date=2008-12-18 |url-status=dead |archive-url=https://web.archive.org/web/20100602050632/http://www.emporia.edu/earthsci/student/geller2/cascadia.html |archive-date=2010-06-02 }} USGS</ref> Major cities affected by a disturbance in this subduction zone include [[Vancouver]] and [[Victoria, British Columbia]]; [[Seattle]], Washington; and [[Portland, Oregon]].