Learning from Experience - Volcanoes

How did the Cascade Volcanoes Form?

The volcanoes of the western United States are the result of subduction of the Juan de Fuca and Gorga plates beneath the edge of the North American Plate. The oceanic plates are made at mid-ocean ridges (spreading centers) and are denser than the North American Plate. The North American Plate is made of continental crust and lithospheric mantle. Water from the oceanic plate helps to melt the hot asthenospheric mantle beneath the North American Plate. Magma rises through the plate to supply volcanoes. (From VolcanoWorld)

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