Climate
The town of Carlsbad is scorching hot during the summer, with temperatures above 100 degrees F 38 degrees C common, but conditions at the park itself are slightly more moderate, although still hot. The fact that the visitor center, at the entrance to the Big Cave, is at somewhat elevated altitude offers some relief from the heat. Winters in the park are usually quite pleasant, with daytime highs around 60 to 65 degrees F 15 to 18 degrees C. Precipitation is sparse, but often comes in the form of brief but incredibly intense summer thunderstorms that may drop up to 4 inches 10 cm of rain in a few hours. There is occasional, non-persistent snow during the winters. Spring and fall tend to have agreeable temperatures and little precipitation, although springtime winds can be unpleasant.
Flora and fauna
Flora and fauna of Carlsbad are typical of the Chihuahuan Desert, with relatively few large animals and plant life that is adapted to the dry environment. Practically every plant species in the park has spines or thorns on it, and the prickly-pear cactus, ocotillo and lechuguilla are widespread and difficult to hike through.
The caves themselves are the home of a distinctive fauna including cave crickets that have adapted to conditions of total darkness. Raccoons, ring-tail cats, and skunks are often found around the cave entrances. By far the best known park denizens, however, are the enormous colonies of Mexican free-tailed bats that live in the Big Cave and other caves see below under "See". Less benignly, rattlesnakes are common in the area, particularly around the entrances to backcountry caves.
History
The existence of caves in the limestone around Carlsbad has been known for a long time, but Carlsbad Caverns was added to the national park system as a National Monument in 1923, largely and famously through the advocacy and actions of Carlsbad-area cowboy Jim White. It gained full-fledged National Park status in 1930. It was designated a World Heritage Site in 1995.
Geology
The Big Room is often described as the world's largest cave chamber, but it no longer holds that title; the record-holding Sarawak Chamber in Lubang Nasib Bagus "Good Luck Cave" in Malaysia is far larger, and as many as 10 other chambers are now known that are larger than the Big Room. However, Carlsbad Caverns still offers world-class cave experiences by any reasonable definition. The "Big Cave" Carlsbad Cavern itself is one of over 80 caves within the park, but it is neither the longest nor the deepest of the park's caves. Both of these honors fall to Lechuguilla Cave, a "wild" cave not normally open to tourists.
The caves lie primarily within a Permian limestone reef, but one unusual feature of Carlsbad Caverns is that it is located atop a field of natural gas and oil. As a result, the usual calcium-carbonate cave formations are supplemented in some areas by formations based on calcium sulfate gypsum created by the migration of sulfur-bearing water up from the gas field. This, combined with a tendency for the limestone containing the bulk of the caves to fracture along massive joints, results in the unusual combination of very large cave passages and extremely ornate although, in many cases, famously massive decorations. The calcium-sulfate formations tend to be delicate and are not usually visible to the casual visitor, but some of the backcountry caves see under "Do" have astonishing calcium-sulfate formations.
Landscape
The park is located where the plains of the Chihuahuan Desert meet the Guadalupe Mountains and ranges in elevation from about 3,200 feet 1,000 m to 5,500 feet 1,600 m. The primary natural entrance to the Big Cave is in a depression in a mesa on the side of Walnut Canyon, which contains the main entrance road to the park. Several of the accessible "wild caves" are in a detached region of the park containing Slaughter Canyon, one of the typical -- and typically rugged -- canyons descending from the Guadalupes onto the plain.