Cliff and columnar basalt, Devil’s Postpile National Monument, California
This small national monument near Mammoth Lakes in the eastern Sierra Nevada is celebrating its centennial this week. It was spared a watery burial one hundred years ago today when congress saved it from a proposed dam on July 6, 1911.
Its unusual basalt columns are the by-product of an ancient lava lake, which rapidly formed and then cooled leaving behind the perfectly shaped hexagonal pillars that make up the cliff. The constant force of winter freeze and thaw is slowly eroding the formation, and the symmetrical blocks that look as though they were snapped together are littered at its base like a child’s building blocks.
The road to the monument, which is closed in winter but easily accessible the rest of the year, is just past the Mammoth Mountain ski area and is also the jumping off point for the popular Minarets and Ansel Adams Wilderness.
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