What formed Mount Rainier?

Answer 1

Mount Rainier, along with the other Cascade volcanoes, was formed as a result of a subduction zone. Off the coast in this region the small Juan De Fuca Plate, composed of oceanic crust, is colliding with and sliding under the continental crust of the North American Plate. As this plate descends into the mantle seawater and other volatiles seep into the superheated mantle rocks, altering their chemistry and allowing them to melt despite the immense pressure. This molten rock, called magma rises through the crust, aided by cracks and emerges on the surface during volcanic eruptions. Material from these eruptions piles up into volcanic mountains.

Answer 2

Mount Rainier was formed by a series of volcanic eruptions that built up layers of lava, ash, and debris over millions of years. The mountain is a stratovolcano, which means it is composed of alternating layers of hardened lava flows, volcanic ash, and debris. The most recent major eruption of Mount Rainier occurred around 1,000 years ago.

Answer 3

Mount Rainier is itself a volcano. It was not formed by other volcanoes.