A wonderland of water-molded rock, Carlsbad Caverns is a vast underground expanse of limestone eroded away over millennia by seeping rainwater. What sets it apart from many other caves, though, is less its huge size than its spectacular ornamentation: The slow deposition of calcite has formed innumerable varieties of stalactites, stalagmites, columns, and an endless array of other structures both huge and delicately tiny. Trails, lights, and an elevator have made the main caverns’ depths accessible to all.
The 83 separate caves found on the 46,000 desert acres of Carlsbad Caverns National Park reach as deep as 1,597 feet below the ground. One, lovely Slaughter Canyon Cave, is open to visitors on a strenuous ranger-guided walk. The limestone of the caverns was formed in an inland sea about 250 million years ago as part of a 400-mile-long reef-like structure, similar to the modern Australian Great Barrier Reef. The fossil remains of marine organisms, such as corals, shells, and algae, are visible in the rocks today. After the sea evaporated, the area was uplifted and fractured; caverns formed where groundwater seeped through the cracks. Two of the most striking formations in the caverns are the Giant Dome, Carlsbad’s largest stalagmite, and the Chinese Wall, a beautiful "rimstone dam" (a wall of calcium carbonate that once rimmed a pool of water).
Wildlife of Carlsbad Caverns
Hundreds of thousands of Brazilian Free-tailed Bats roost in Carlsbad's main cave from April through October, hanging from the ceiling in densities as great as 300 per square foot. Their nightly emergence from the entrance is one of North America’s great wildlife spectacles, coming as it does soon after the caverns’ lesser but still considerable numbers of Cave Swallows have flown in for the evening. Other bats include the Fringed Myotis, which has been found as far as 1,000 feet below ground level. White-footed Mice, Ringtails, and Common Raccoons are among the other animals that have colonized deep reaches of the cave.
Underground caverns form when acidic groundwater percolates through underlying limestone and gradually dissolves the stone. The water eventually drains away, revealing passageways and hollow rooms. In the later stages of cavern formation, lime-rich water drips down into the caverns and evaporates, leaving behind tiny crystals of calcium carbonate that grow into stalactites (icicle-like deposits hanging from the ceiling), stalagmites (columns rising up from the cave floor), and other cave formations, collectively called speleothems.
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