With a volume of 8 to 9 km3 (1.9 to 2.2 cu mi), Mount Bailey is slightly smaller than neighboring Diamond Peak.

According to Klamath tradition, their medicine men and priests would feast on the mountain's summit and commune with the upper world.

Over time, as the range built up, newer activity diminished older Tertiary age rock.

Creating lava plateaus, Pliocene activity, mostly basaltic and andesitic, was probably responsible for the original cones at Bailey, Thielsen, and Union Peak.

[8] Bailey is comprised by a central tephra cone, upon which basaltic andesite eruptions streamed over, building up to create the current volcano.

[9] It is currently inactive, having been since approximately the time Mount Mazama became active, sometime in the early Pleistocene epoch.

[11] Bailey is a popular hiking and skiing site, due to its steep climbs and views of Diamond Lake.