Climate
Valles Caldera has a continental climate with four distinct seasons. Winter weather is highly variable, with some years producing a great deal of snow over four feet of snow has fallen in a single storm and other years producing almost none at all. Winter highs in the valleys are typically around 35-40 degrees Fahrenheit and lows in the single digits, although there are isolated cold pockets from cold air coming off the mountains. December is often the coldest month and can see sub-zero temperatures at night. Snow in the valleys usually melts completely around April, and spring characterized by high winds. This combination can create nasty forest-fire hazard in May and June, particularly following a dry winter. Winds die down somewhat by June, which is warm highs in the 70s-80s and dry. Monsoon conditions develop in July and persist until around the beginning of September, leading to cooler temperatures highs in the 70s, lows around 50 and spectacular afternoon thunderstorms that urge the hiker to be off the trails by early afternoon. This is a great time to visit, but make sure you bring raingear and start your day early. The thunderstorms usually die out by Labor Day or so, leading to autumn conditions that are temperate, dry apart from the occasional frontal storm system and generally very pleasant. The first snowfall is commonly in October, but snow doesn't start to stick until Thanksgiving or so. Conditions on the mountains are similar but 10 degrees cooler, with more rain and snow.
Flora and fauna
The valleys are grasslands, while the mountains are covered with coniferous forest and aspens. New Mexico's largest herd of elk spends its summers in the Preserve, migrating to lower elevations for winter. Deer and black bear are also encountered, and there are a few mountain lions, although they are almost never seen by visitors. Smaller animals include the ubiquitous coyote, porcupine, skunk, raccoon, and all manner of rodents.
Birdwatching in VCNP is good, although not as diverse as along the nearby Rio Grande. Many species of raptors are present and can often be seen perched on dead timber or gliding above the valleys looking for prey, as can black vultures. Two of the most characteristic birds of VCNP, at opposite ends of the size scale, are the huge black ravens that compete for offal with the vultures, and several species of hummingbirds that may zing past you as you hike or ride. The raptors, vultures and ravens are residents year-round, but the hummers are migratory and head south around the beginning of September.
There are few snakes in VCNP, as the elevation is too great for most of them. However, timber rattlesnakes have been seen on occasion even near the top of the ski runs on Pajarito Mountain elevation 10,409' on the eastern rim above Los Alamos. The endangered Jemez Mountain salamander is present and could lead to occasional closures of parts of VCNP to preserve its habitat. Trout swim in the streams that have their headwaters in the region, some of which are suitable for fishing permit system.
History
The Valles Caldera has had an unusual history that has given it a unique position among United States national parks. After a long pre-history of occupation by ancestral Puebloans and later Spanish settlers, the caldera and the surrounding Jemez Mountains passed into United States control after the Mexican-American War. At this time it wasn't viewed as particularly significant: a remote, if scenic, area of what seemed to be grazing land within a newly-acquired territory, of little commercial interest to anyone but the old Spanish families that had already settled and pastured livestock there, sometimes in the face of considerable hostility from nearby Indian populations. Consequently, when a bill was passed in the United States Congress in 1860 to compensate the Baca family, a pioneering family in New Mexico with significant land holdings, for the federalization of some of their land, a large tract of land in the Jemez, including most of the caldera, was handed over to the Bacas, along with some other tracts elsewhere in the Southwest. This tract became known as "Baca Location No. 1" and would retain this name long after the Baca family sold it to other investors.
The Baca Location changed hands a few times in the 19th and 20th centuries before winding up in the hands of James P. Pat Dunigan, a wealthy Texan who had a good sense for the history and aesthetics of the property. Dunigan was horrified by the environmental damage inflicted on his property by prior holders of the timber rights. He therefore bought out the holders of those rights, and placed most of the Baca Location off limits to development while he negotiated with the United States government to sell the land back to the government under terms that guaranteed its preservation in perpetuity. The negotiations literally took decades, but finally, in 1999, Congress authorized the acquisition of the Baca Location from Dunigan's heirs, as he had died by this time.
The terms of the acquisition called for the resulting "Valles Caldera National Preserve" VCNP to differ from practically any other national park land in the United States, in two related senses. First, in recognition of not only the history of the Baca Location but also the fact that the grazing there is economically significant to the region which cannot exactly be called wealthy, Congress decreed that the Preserve would continue to function as a working ranch, and that it would eventually become self-sustaining through the revenues thus generated, even as resources for public recreational use came on-line. Second, and as a result, management of the VCNP would be done via a "trust" that includes representatives of not only the agencies that contributed land to the Preserve but also members of nearby communities. These factors together explain why visitor facilities have been slow in developing.
The beautiful terrain has led to the area being used as background for a number of movies some quite recent, and old, decaying movie sets are scattered around the valleys. Some are accessible via trail rides or hikes, but please don't touch; they're scenic, but generally in such rickety shape as to be hazardous.
Landscape
The terrain is volcanic with the caldera rim topping out at elevations around 10,500 feet. Chicoma Mountain (11,590 and a few other points along the northeastern rim reach over 11,000', but lie outside the Preserve, on the territory of Santa Clara Pueblo.) The caldera itself has a base level at 8700' and is broken into a collection of valleys by resurgent domes and post-caldera eruptive centers. The largest valley is the Valle Grande, on the southeast side of the caldera; the highest summit within the caldera, and the highest in the Preserve, is Redondo Peak, with a summit elevation above 11,200 feet. Note that Redondo Peak is considered a sacred mountain by a number of the American Indian tribes of the region, and its summit is off limits to hikers. El Cajete is a relatively recent ~60,000 years old? eruptive center southwest of Valle Grande that is reachable by an attractive Nordic ski trail.
Most of the mountains in VCNP are fairly gentle, although there are a few basalt outcroppings that produce cliffs. These cliffs are not yet open to the public for rock climbing, but similar formations in the surrounding Santa Fe National Forest and in nearby Los Alamos are popular attractions for the technical sport climber. The territory outside the caldera features a vast region of eroded tuff known as the Pajarito Plateau, with spectacular canyon-mesa scenery. Los Alamos is built on the Pajarito Plateau, and many of the formation's canyons are preserved in Bandelier National Monument which abuts VCNP on the south. The drive to VCNP from the east Los Alamos side shows this terrain to breathtakingly good advantage.