Researchers have determined that the columns were created by cold water percolating down into — and steam rising up out of — hot volcanic ash spewed by a cataclysmic explosion 760,000 years ago
The blast, 2,000 times larger than the 1980 eruption of Mt. St. Helens, created the Long Valley Caldera, a massive 10-by-2-mile sink that includes the Mammoth Lakes area. It also covered much of the eastern Sierra Nevada range with a coarse volcanic tuff, or ash fall.
[Found here via here. Caption from here.]
Tacky Raccoons 