The battling forces of fire and ice created the Devils Postpile: over 400 unusually symmetrical columns of basalt towering six hundred feet high, on the eastern side of the sierras, just outside of Mammoth.
The columns began forming roughly a hundred thousand years ago when a large lava flow from the Upper Soda Springs area began cooling. As the molten lava cooled slowly and evening, vertical joints – cracks in the rocks due to expansion – formed the multi-sided columns. The basalt columns -- like the giant's causeway in Ireland -- formed naturally into hexagonal columns. The columns then came into contact with a massive moving glacier that left highly visible glacial striations and a glacial polish.
Three geologic features make the Devils Postpile unique. First, the lack of common horizontal jointing. Second, the uncommon symmetry of the columns are found only a few places throughout the world, Finally, the visible marks left by the glacial movement.
The Devils Postpile has twice been threatened with destruction. The first, in the late 1800s, was when gold was found near Mammoth and the area around the Devils Postpile were removed from the sanctuary of Yosemite National Park. Luckily, the columns were spared being dynamited in the search for gold.
The second threat, in the early 1900s, was when a proposed hydroelectric dam called for the destruction of the postpile. Thanks to the persuasive voice of Californian Walter L. Huber, president Taft turned the Devils Postpile into a National Monument in 1911.
Today the Devils Postpile National Monument offers an active hiking and camping locations and breath taking view including that of the 100 foot Rainbow Falls.