Walls of Crater Lake Caldera

February 08, 2006

Backboneepod2 copy

Provided and copyright by: Steve Kluge, Fox Lane High School
Summary authors & editors: Steve Kluge

The dramatic eruption and subsequent collapse of Mt. Mazama 7,000 years ago uncovered a remarkable cross section of the structure of that volcano, which is visible today on the inner walls of Crater Lake caldera in southwestern Oregon. During the final stages of Mt. Mazama's existence, pressures within the mountain caused large, radial cracks to form within it. In some instances those cracks were forced open and filled with hot, molten rock that later cooled and crystallized into huge vertical slabs of resistant rock, forming what geologists call radial dikes. Devil's Backbone is one of those dikes, standing tall and strong on the western shore of Crater Lake as the softer pumice and lava flows that once enclosed it weather away. The left hand image was taken in the late morning from the rim of the crater, leaving the side of the 'Backbone' facing the camera in the shade. The right hand image (a composite of 2 photos) was taken from the lake later in the afternoon. Note that the triangular slab in the foreground of this image stands 130 m tall (427 ft), dwarfing the pine trees that grow on and around it.

Mt. Mazama/Crater Lake is one of the Cascade Volcanoes of the U.S. Pacific Northwest. The Google Earth tour linked below begins and ends with a view of the Cascade Range.

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