Carlsbad Cavers, located in the Guadalupe Mountains of New Mexico was created some 250 to 280 million years ago. Under laying the rugged desert landscape is one of the most important geologic resources in the United States. The Guadalupe Mountains are the uplifted portion of an ancient reef the thrived along the edge of an inland sea more then 250 million years ago. Preserved in the rocks are the bodies of sponges, algae, snails, nautilus, and many other animals that lived in this sea.

The most famous of all the geologic features in the park are the caves. Carlsbad Caverns National Park contains more than 110 limestone caves.  The 110 caves of Carlsbad Caverns Nation Park were not carved out by running water like so many limestone caves, but were opened up by some a very aggressive sulfuric acid, working on the limestone layers. Elevations in the park rise from 3,595 feet in the lowlands to 6,520 atop the escarpment. Though there are scattered woodlands in the higher elevations, the park is primarily a variety of grassland and desert shrubland habitats.

Take a look at: http://www.nps.gov/cave/index.htm