Valles Caldera - Geology and Science

Geology and Science

Valles Caldera is one of the smaller volcanoes in the supervolcano class. The circular topographic rim of the caldera measures 19 kilometers (12 miles) in diameter. The caldera and surrounding volcanic structures are the most thoroughly studied caldera complex in the United States. Research studies have concerned the fundamental processes of magmatism, hydrothermal systems, and ore deposition. Nearly 40 deep cores have been examined, resulting in extensive subsurface data.

The Valles Caldera is the younger of two calderas known at this location, having collapsed over and buried the Toledo Caldera, which in turn may have collapsed over yet older calderas. The associated Cerros del Rio volcanic field, which forms the eastern Pajarito Plateau and the Caja del Rio, is older than the Toledo Caldera. These two large calderas formed during eruptions 1.47 million and 1.15 million years ago. The Caldera and surrounding area continue to be shaped by ongoing volcanic activity. The El Cajete Pumice, Battleship Rock Ignimbrite, Banco Bonito Rhyolite, and the VC-1 Rhyolite were emplaced during the youngest eruption of Valles caldera, about 50,000–60,000 years ago. Seismic investigations show that a low-velocity zone lies beneath the caldera, and an active geothermal system with hot springs and fumaroles exists today.

The volcanic properties of the Valles Caldera make it a likely source for renewable and nonpolluting geothermal energy. However, some people oppose development of the geothermal energy, considering it destructive to scenic beauty and recreational and grazing use.

The lower Bandelier tuff which can be seen along canyon walls west of the Valles Caldera, including San Diego Canyon, is related to the eruption and collapse of the Toledo Caldera. The upper Bandelier tuff is believed to have been deposited during eruption and collapse of the Valles Caldera. The now eroded and exposed orange-tan, light-colored Bandelier tuff from these events creates the stunning mesas of the Pajarito Plateau.

These calderas and associated volcanic structures lie within the Jemez Volcanic Field. This volcanic field lies above the intersection of the Rio Grande Rift, which runs north-south through New Mexico, and the Jemez Lineament, which extends from southeastern Arizona northeast to western Oklahoma. The volcanic activity here is related to the tectonic movements of this intersection.