The volcano lies at the northern end of the 15-mile (24 km) long Mount Bachelor Volcanic Chain, which underwent four major eruptive episodes during the Pleistocene and the Holocene.

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).

[11] Constructed towards the end of the Pleistocene Epoch, these mountains are underlain by more ancient volcanoes that subsided due to parallel north–south faulting in the surrounding region.

[14][16] Most of the surrounding volcanoes consist of mafic (rich in magnesium and iron) lavas;[16] only South and Middle Sister have an abundance of silicic rocks such as andesite, dacite, and rhyodacite.

[6] Despite the small scale of this erosion, it has extensively altered the northern face of Mount Bachelor, breaking down its lava into fine powder, particularly at the glacier terminus, where the terminal moraine resembles dust.

There is no geothermal activity at present, though some areas popularly thought to be fumaroles are caused by air movement through the porous structure.

[13] Within the Bachelor chain, mafic (rich in magnesium and iron) eruptive activity consisting mostly of lava flows and tephra fall[5] took place over four discrete periods,[31][32][b] beginning approximately 18,000 to 15,000 years ago as a Pleistocene glacier in the area began to retreat.

[19][33] During this first eruptive episode, the majority of activity occurred in the center of the chain, forming the Sheridan Mountain shield volcano.

[25] Hyaloclastite deposits and thick lava flows with ice also formed in this area,[19] along with the Talapus and Katsuk Buttes from scoria produced by later, milder Strombolian eruptions (which eject incandescent cinder, lapilli, and volcanic bombs).

[25] By 12,000 years ago, Mount Bachelor was close to its current size, as the oldest moraines from glaciers on the mountain (which are covered by lava flows from this third eruptive episode) can be dated to this time period.

Because lava flows move slowly, they can be outmaneuvered by animals and humans, though they do pose a threat to streams and rivers, which they may dam or divert, leading to potential flood risks.

During the war, Bend's community depended on sawmills and agriculture, with a small ski area opening at Mount Bachelor in 1941.

[2][4] In the 1980s, struggles of the homebuilding and lumber industries meant that Deschutes County saw a 15 percent unemployment rate, but construction of a local mall, a chair to the top of Mount Bachelor, and the High Desert Museum helped the economy improve with time.

[9] In 2013, the United States Forest Service approved a new master plan for further development of the resort, including a mountain bike park, more chair lifts, more trails, a zip line, and improved lodge amenities.

[37] The volcano's summit hosts the Mount Bachelor Observatory, located at an elevation of 9,000 feet (2,700 m) above sea level, and maintained by a research group at the University of Washington Bothell and the ski resort.

Research at the observatory investigates long-range transport of pollution from the Asian continent, measuring chemical features of plumes that reach the Pacific Northwest.

[26] Nationally known,[41] the resort is one of the largest in the Pacific Northwest with a skiable area of 3,683 acres (14.9 km2) and a vertical drop of 3,365 feet (1,026 m),[40] in addition to six terrain parks.

The resort offers interpretive tours with a naturalist on local flora and fauna,[43] in addition to snowshoeing,[44] snowboarding,[45] snow tubing, dog sledding, and department stores.