Mount Bachelor, formerly named Bachelor Butte, is a dormant stratovolcano atop a shield volcano in the Cascade Volcanic Arc and the Cascade Range of central Oregon, United States. Named Mount Bachelor because it stands apart from the nearby Three Sisters, it lies in the eastern segment of the central portion of the High Cascades, the eastern segment of the Cascade Range. The volcano lies at the northern end of the long Mount Bachelor Volcanic Chain, which underwent four major eruptive episodes during the Pleistocene and the Holocene. The United States Geological Survey considers Mount Bachelor a moderate threat, but Bachelor poses little threat of becoming an active volcano in the near future. It remains unclear whether the volcano is extinct or just inactive.
The Mount Bachelor ski area has operated on the mountain since 1958, and the volcano's summit hosts the Mount Bachelor Observatory. A center of winter recreation, the area offers alpine skiing and snowboarding, cross-country skiing, and dog sledding, among other activities. The summit can be reached by a climbing trail that travels over lava from the volcano.
Geography
Mount Bachelor lies in the Cascade Range, within Deschutes County, in the U.S. state of Oregon. and reaches an elevation of .
Weather varies greatly in the area due to the rain shadow caused by the Cascade Range. Air from the Pacific Ocean rises over the western slopes, which causes it to cool and dump its moisture as rain (or snow in the winter). Precipitation increases with elevation. Once the moisture is wrung from the air, it descends on the eastern side of the crest, which causes the air to be warmer and drier. On the western slopes, precipitation ranges from annually, while precipitation over the eastern slopes varies from in the east. Temperature extremes reach in summers and during the winters.
Geology
thumb|upright=1.2|Topographic map of area (with Bachelor near bottom center)
Mount Bachelor joins several other volcanoes in the eastern segment of the Cascade Range known as the High Cascades, which is the largest Mount Bachelor formed between 18,000 and 8,000 years ago. Bachelor is composed of basalt and basaltic andesite, there is also little pyroclastic rock. There is no summit crater.
Lava flows from Mount Bachelor's summit feature phenocrysts including clinopyroxene, olivine (more rare), and plagioclase, with two phases for the clinopyroxene featuring augite and pigeonite. Textures for these eruptive products vary from intersectal to intergranular, seriate to glomeroporphyritic to subophitic, and trachytic to non-aligned.
Bachelor last erupted between 10,000 and 8,000 years ago, and is entirely covered with Mazama Ash from the catastrophic eruption of Mount Mazama about 6,845 years ago. There is no geothermal activity at present, though some areas popularly thought to be fumaroles are caused by air movement through the porous structure. beginning approximately 18,000 to 15,000 years ago as a Pleistocene glacier in the area began to retreat. Mount Bachelor poses little threat of becoming an active volcano in the near future. If Mount Bachelor were to erupt, it would significantly affect the ski industry on the volcano, endangering visitors. An eruption from Mount Bachelor, the Three Sisters to the north, or another nearby vent in the Mount Bachelor Chain may be unlikely, but any would pose threats to the ski area. Expansion continued into the 1970s, with the ski area receiving 257,000 visitors between 1974 and 1975, and more than 500,000 between 1982 and 1983.
Recreation
thumb|right|The chair lift to Mount Bachelor's summit, as seen in 1986
Mount Bachelor ski area operates a chairlift during the summer as well as during the ski season (weather permitting), in addition to six terrain parks. The resort represents a center of winter recreational activities within Deschutes County, operating within the Deschutes National Forest and partnering with the United States Forest Service to offer activities while preserving the Oregon Cascades and the forest area. The resort offers interpretive tours with a naturalist on local flora and fauna, in addition to snowshoeing, snowboarding, snow tubing, dog sledding, and department stores. During the summer, fishing is a popular activity in the local lakes and streams, as is hiking and camping.
Climbing to the top of Mount Bachelor follows a trail that begins at an elevation of and gains to reach the summit. A single-track trail, it traverses over lava from the volcano, which appears in jagged formations. The volcano's summit offers views of the rest of the Mount Bachelor chain to the south, in addition to Lookout Mountain,