Valle Grande,

Valle Grande, N.M., near Los Alamos

Valle Grande Supervolcano

Country:	United States
Subregion Name:	New Mexico (USA)
Volcano Number:	121002-D
Volcano Type:	Caldera
Volcano Status:	Pleistocene-Fumarolic
Last Known Eruption:	Pleistocene
Summit Elevation:	3430 m	11,253 feet
Latitude:	35.87°N	35°52'0"N
Longitude:	106.57°W	106°34'0"W
The 22-km-wide Valles caldera was formed as a result of two large volume eruptions that created the widespread Bandelier Tuff ignimbrite plateaus on all sides of the caldera. The lower member of the Bandelier Tuff, the Otawi, was emplaced about 1.7 million years ago (Ma) and resulted in the formation of most of the present-day Valles caldera, including the Toledo embayment at the NE side. The upper member, the Tshirege, is dated about 1.2 Ma, and also deposited voluminous welded pyroclastic flows over about the same area as the Otawi member. Post-caldera volcanism has included the emplacement of multiple ring-fracture lava domes and uplift of the caldera floor, forming the Redondo Peak resurgent dome. 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 one million-year-old Valles Caldera (15-mi diameter) is the centerpiece of the Jemez Volcanic Field in North Central New Mexico. The caldera was formed when the volcanic pile collapsed in response to a huge eruption of ash from the magma chamber.

Valle Grande Supervolcano

http://www.vallescaldera.gov

credit: NASA, The Discovery Channel, The Smithsonian Institute, USGS