Cathedral Valley, Capitol Reef National Park, 2012.

Glass Mountain (foreground) is made of large gypsum (selenite) crystals deposited when seawater evaporated around 165 million years ago. After deposition and burial under rock layers, the gypsum began to move slowly upward along faults and fractures, sometimes forming small domes. Glass Mountain is one of those domes, rising 15 feet above the valley floor. Gypsum is water-soluble and over time precipitation will most-likely dissolve it to create a sinkhole.