Pajarito Plateau
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The Pajarito Plateau is a region in New Mexico, United States on the east side of the Jemez Mountains. Bandelier National Monument, the towns of Los Alamos and White Rock (officially a part of Los Alamos although some miles away from it), and Los Alamos National Laboratory are situated on the plateau, which is bounded on the south and east by the Rio Grande. Elevations range from about 5600 feet (1700 meters) at the river to about 7800 feet (2300 meters) where the plateau merges into the mountain range.
The Pajarito Plateau is primarily composed of ignimbrite, a voluminous deposit of volcanic tuff laid down in an explosive eruption — in this case, a pair of eruptions from the nearby Valles Caldera. The two ignimbrite-forming eruptions occurred about 1.4 million and 1.1 million years ago and ejected about 300 cubic kilometers of rock each. The orange-pink rock formations constituting the resulting ignimbrites are known as the Otowi and Tshirege Members of the Bandelier tuff. The soft, friable tuff is stabilized by basalt flows that interleave with the ignimbrites. Erosion has created a maze of canyons up to 800 feet (240 meters) deep that divide the plateau into mesas. (As some mesas climb on the western side rather than descending on all sides, some people prefer to call them by the local Spanish word potrero.) The result is a highly scenic area well endowed with hiking trails, some of which reach the Rio Grande. Rock climbing is also done on the basalt cliffs that intrude into the tuff, which itself is too soft to be climbed safely.
The region is sparsely inhabited outside Los Alamos and White Rock, and wildlife is abundant and diverse. A large elk herd that spends its summers in the Jemez Mountains descends to the Pajarito Plateau during the winter, creating a significant driving hazard. Deer, black bear and coyote are common, and the plateau and mountains support a small but significant population of mountain lions, which have on occasion been known to attack humans. Smaller mammals such as raccoons and skunks are commonly encountered. Parts of the Bandelier backcountry have been closed seasonally due to nesting bald eagles. The Rio Grande supports a significant migratory flyway that brings many other birds (notably sandhill cranes) to the plateau during migration seasons, and three species of hummingbirds are abundant during summer. White Rock Canyon, the major canyon containing the Rio Grande into which the plateau's canyons empty, is notorious for rattlesnakes.
