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Valles Caldera |
Valles Caldera (or Jemez Caldera), is a very large volcano (a supervolcano) at the heart of the Jemez Mountains of northern New Mexico. Within its caldera, Valle Grande1 is the largest valle (grass valley) and the only one with a paved road.
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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 25 July 2000, the Valles Caldera Preservation Act, 16 U.S.C. Sections 698v-698v-10, created the Valles Caldera National Preserve. Noting that 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, thereby serving as a model for self-sustaining land development and use.2 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.3 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).4 It is administered from United States Forest Service offices in Jemez Springs.
Valles Caldera is one of the smaller volcanoes in the supervolcano class. The circular topographic rim of the caldera measures 22 kilometers (14 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.5
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.67
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.89 The largest meadow, Valle Grande, is a venue for ski orienteering. The orienteering map was developed by New Mexico Orienteers.10
Valles Caldera has provided several filming locations,11 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".
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