Geology and Minerals

Cascade Volcanic Arc calderas

The Cascade Volcanic Arc is a chain of volcanoes stretching from southern British Columbia down to northern California. Within the arc there is a variety of stratovolcanoes like Mount Rainier and broad shield volcanoes like Medicine Lake. But calderas are very rare in the Cascades, with very few forming over the 39 million year lifespan of the arc. The few eruptions that do form calderas rarely make it into the VEI 7 range, staying confined to the VEI 6 range in most cases. The only volcanoes known to have produced eruptions within the VEI 7 range are Crater Lake, the Mt. Baker Volcanic Field, and the Lassen Volcanic Center. All of the exceptionally large caldera-forming eruptions within the cascades erupted silica-rich magmas, with the three VEI 7s erupting mainly rhyodacite and rhyolite.

Also on this shelf

See also

• ▸Biogenic substance
• ▸Garibaldi Volcanic Belt
• ▸Alluvial fan

Uncatalogued shelf

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