The Bishop Tuff is a welded ashflow that was deposited ~700,000 years ago (Dalrymple et al, 1965). Here the Owen's River incised the Bishop Tuff exposing beautiful columnar rhyolite. The columnar fracture pattern is made by rapid cooling caused be a fumeral of escaping steam. Water that the Bishop Tuff was deposited over was heated and pressurized, leading to an explosive escape through fumeral mounds that dot the region. The roset, curved jointing is orthogonal to isotherms and tubes of escaping hot water (Sheridan, 1970).
All photos by Timothy Sherry
Dalrymple, G. Brent, Allan Cox, and Richard R. Doell. "Potassium-argon age and paleomagnetism of the Bishop Tuff, California." Geological Society of America Bulletin 76.6 (1965): 665-674.
Sheridan, Michael F. "Fuarmolic Mounds and Ridges of the Bishop Tuff, California." Geological Society of America Bulletin 81.3 (1970): 851-868.