Cerro la Jara, an approximately 75 metre (250 ft) high forested rhyolite lava dome within the caldera.
|Elevation||3,430 metres (11,253 ft)|
|Location||Sandoval County, New Mexico, USA|
|Last eruption||60–50 kyr |
Valles Caldera (or Jemez Caldera), is a 12 mi (19 km) wide volcanic caldera in the Jemez Mountains of northern New Mexico. Within its caldera, Valle Grande is the largest valle (grass valley) and the only one with a paved road.
Until recently, the Valles Caldera was part of the Baca Ranch. The Dunigan family sold the entire surface estate of 95,000 acres (380 km2) and seven-eighths of the geothermal mineral estate to the federal government.
On July 25, 2000, the Valles Caldera Preservation Act, 16 U.S.C. Sections 698v-698v-10, created the Valles Caldera National Preserve. The careful husbandry of the Baca Ranch by its private owners, including selective logging, limited grazing and hunting, and the use of prescribed fire, had preserved a mix of healthy range and timber land with significant biodiversity, including New Mexico's largest herd of elk, and served as a model for self-sustaining land development and use. Funds for the purchase came from the Land and Water Conservation Fund derived from royalties the US government receives from offshore petroleum and natural gas drilling. Under the terms of the Act, the Preserve will have to produce sustaining income; environmentalists had lobbied for the more inclusive protections of National Park status instead. The preserve is located in northeastern Sandoval County and southern Rio Arriba County, just west of Los Alamos. It has a land area of 89,716 acres (140.18 sq mi, or 363.07 km2). It is administered from the offices of the Valles Caldera Trust in Jemez Springs.
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.
A number of recreational and/or historical uses take place in the Valles Caldera. Many of these uses involve trails. Valles Caldera has many miles of ranch roads and livestock and game trails. These include a network of trails currently designated for horse riding. Historically, Valles Caldera was a location for equestrian endurance races. After establishment of VCNP the first race in the caldera was held in 2009. The largest grass valley, Valle Grande, is a venue for ski orienteering.
Throughout the caldera the grass valleys appear groomed: there are few saplings and mature trees lack lower branches. This is due to heavy browsing by elk and cattle. Although the grass appears abundant, it is a limited resource. Its growing season is short, it feeds thousands of cattle in the summer and more thousands of elk all year, and during most of the year its nutritional value is low.
Valles Caldera has provided several filming locations, most for films in the Western genre. Some of these locations include exterior sets, such as the weathered "ranch house" that can be seen from the highway in Valle Grande, and a small "town".