Gibraltar Rock, Mount Rainier

March 01, 2002


Provided by: Tim Martin, Greensboro Day School
Summary authors & editors: Tim Martin

Mount Rainier like many of the volcanoes of the Pacific Northwest is a stratovolcano. This image of Gibraltar Rock was taken from atop Disappointment Cleaver (elevation 12,300’) on the east side of Mount Rainier. The Ingraham glacier has eroded the north side of Gibraltar Rock exposing the eruptive history of Mt. Rainier.

Stratovolcanoes also known as composite cones, are built up with alternating layers of lava flows and tephra. The layers of ash and tephra are much softer. The erosion of this volcanic tuff is responsible for the undercut stair steps seen on the east (left) side of this image.

In the background, Mount Adams (elevation 12,276’) rises above the Cascade Range.

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