Thick deposits of welded pumice form cliffs along the Jemez River valley SW of the Valles caldera, capping darker-red, bedded sedimentary rocks at the base of the canyon. The lowermost pyroclastic-flow deposit, showing pronounced columnar jointing, is the Otowi member of the Bandelier Tuff. The top of the section is the Tshirege member of the Bandelier Tuff. The two eruptions, about 1.45 and 1.1 million years ago, ejected about 600 cu km of magma and resulted in the formation of Valles caldera.

Photo by Lee Siebert, 1989 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Valles Caldera