Pacific NW—The Cascadia Subduction Zone (geomorphology)

2min 41s Novice

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What does the landscape reveal about geologic processes?

The Cascadia Subduction Zone of the Pacific Northwest is comprised of a collection of major geographic features, including the subducting plate, the subduction plate boundary, the Coast Range, the Puget-Willamette lowlands, and the Cascades Mountain Range.

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Keypoints:

All these geographic features are related to the subduction zone:

  • Offshore plate boundary (often accompanied by a trench when older cold oceanic plate dives beneath another oceanic plate or continent. The Juan de Fuca Plate is young and warm, so doesn't result in such a trench as it doesn't dive as steeply)
  • Coast Range due to compression of the plate
  • Central valley, which is caught between the Coast Range and the
  • Arc Volcanoes, which grow above the point where the subducting plate reaches about 100 km depth. Melting of the rock requires a particular pressure/temperature regime.

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