

Photographer: Nel Graham

Summary Author: Nel Graham

A short hike to the top of the Devil's Postpile on Mammoth Mountain, in the Sierra Nevada of California, reveals the tile-like pattern shown above. Slow cooling of basalt, from the top down, is responsible for these nearly 120 degree shrinkage cracks. The top of the posts were scoured by glaciers during the last glaciation. Visible on the tiles faces are glacial striations, which show the direction of motion of the glacier. A water bottle was placed for scale purposes. Photo taken in July 2008.

Photo Details: Camera: Panasonic DMC-TZ4; Focal Length: 4.7mm (35mm equivalent: 28mm); Aperture: f/8.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 100.

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