Mount Rainier was formed not in one great cataclysm, but by many years of volcanic activity. It is a composite volcano (or stratovolcano) made from sluggish, intermittent lava flows and explosive eruptions of ash and rock. ... Tons of rock, mud and debris rolled down the peak's northeast flank.

What plates formed Mount Rainier?

Mount Rainier (Figure 2.1) is one of about two dozen recently active volcanoes in the Cascade Range, a volcanic arc formed by subduction of the Juan de Fuca plate beneath the North American plate.

Was Mt Rainier created by a volcano?

Mount Rainier is an episodically active composite volcano, also called a stratovolcano. Volcanic activity began between one half and one million years ago, with the most recent eruption cycle ending about 1,000 years ago.