Mount Bachelor is a dormant stratovolcano in central Oregon’s High Cascades, standing apart from the nearby Three Sisters and anchoring the northern end of a fifteen-mile volcanic chain in the Deschutes National Forest. Built mainly of basalt and basaltic andesite atop a shield volcano, it formed between about eighteen thousand and eight thousand years ago, with its present shape largely established by roughly ten thousand years ago. Unlike many Cascade peaks, it has seen only limited glacial erosion. Though classed by the U.S. Geological Survey as a moderate volcanic threat, it is best known today for recreation, including a ski area, observatory, and summit trail.