Geography and Geology
Mount Bailey is part of the High Cascades in the western United States. The High Cascades have long been glaciated, by both Pacific-bred storms and natural, elevation-caused, glaciation. In fact, glaciation probably formed on them as early as the late Miocene. 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.
Mount Bailey heads the Mount Bailey chain, which consists of the mountain and smaller cinder cones trending north. Similarly to its neighbor Mount Thielsen, it is a shield volcano with precipitous summit slopes, and the two are almost equal in appearance. Built around the same time as Rodley Butte, according to morphological study, the current volcano is no more than 100,000 years old, and formed relatively close to Diamond Peak's current cone. Despite its similarity to Rodley Butte, both in age and original composition, Bailey switched from erupting basaltic andesite to pure andesite (silicon dioxide).
Bailey is comprised by a central tephra cone, upon which basaltic andesite eruptions streamed over, building up to create the current volcano. Eventually switching to andesite, it may have been built over several eruptions or even eruptive periods, judging from the silicic nature of its rock. It is currently inactive, having been since approximately the time Mount Mazama became active, sometime in the early Pleistocene epoch.
Read more about this topic: Mount Bailey (Oregon)
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“The totality of our so-called knowledge or beliefs, from the most casual matters of geography and history to the profoundest laws of atomic physics or even of pure mathematics and logic, is a man-made fabric which impinges on experience only along the edges. Or, to change the figure, total science is like a field of force whose boundary conditions are experience.”
—Willard Van Orman Quine (b. 1908)