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. “These columns are spectacular products of a natural experiment in the physics of hydrothermal convection,” Noah Randolph-Flagg, 25, a Ph.D. candidate and lead author of the study, said in an interview.
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.
Randolph-Flagg said researchers not only discovered the origin of the columns but also learned a great deal about the surrounding landscape. “They have a lot to tell us about what the region was like before and after the caldera exploded, and about how volcanoes can change the local climate,” he said.
The columns began forming as snowmelt seeped into the still-hot tuff. The water boiled, creating “evenly spaced convection cells similar to heat pipes,” according to the study to be presented next month in San Francisco at an American Geophysical Union meeting, the world’s largest conference in geophysical sciences. Analyses by X-rays and electronic microscopes of samples of the columns found that tiny spaces in these convection pipes were cemented into place by erosion-resistant minerals.
Randolph-Flagg estimated that as many as 5,000 columns exist within a 2-to-3 square-mile area east of the lake. They appear in clusters and are diverse in size and shape.
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