The most recent activity was 130,000 years ago. Magma ranging from basalt to rhyolite in composition has been erupted. The volcanic field is best known for the Valles caldera which formed 1.12 million years ago and produced the Bandelier Tuff. The geothermal and hot springs systems are caused by flow of groundwater through the caldera. Some of the water rises to the surface to supply fumaroles and hot springs.
Geothermal activity continues.
Based on the long history of the Jemez volcanic field and past cycles in activity it probably should be considered a dormant volcano that will probably erupt again. Bandelier Tuff in Bandelier National Monument. Photograph by Pranoti Asher, July 1989. Bandelier National Monument preserves village sites of 13th-century Pueblo Indians. Photograph by Pranoti Asher, July 1989.