In the Eastern Sierra, Owens Valley sits the Long Valley Caldera. The caldera was formed 760,000 years ago depositing volcanic ash that was cemented together by heat and pressure. Today a Crowley Lake Reservoir sits in what remains of the caldera. Researchers have determined that the columns were created by cold water percolating down into — and steam rising up out of — hot volcanic ash cemented the ash into more resistant columns that were exposed by wave action of the lake water.