These curved columnar joints in the Bishop Tuff are exposed in Owens River Gorge SW of Long Valley caldera in California. The 5- to 6-sided columns are about 1-3 m wide and curve downward to a common point, forming a feature known as a joint rosette. The rosettes are the site of large fossil fumaroles and often are overlain by fumarole mounds. These mounds may have formed as a result of volatiles produced when the hot Bishop pyroclastic flows overran and vaporized the ancestral Owens River.

Photo by R.V. Fisher, 1984 (University of California Santa Barbara).

This image is made available under the Creative Commons BY-NC-ND 4.0 license terms.

Keywords: outcrop | deposit | pyroclastic flow | tuff | ignimbrite | pyroclastic density current | PDC

Long Valley