The Carlsbad Caverns was acknowledged as a National Monument and it later became a National Park in 1930. The Carlsbad Caverns National Park is a spectacular national park full of fascinating geologic structures, the most renowned of which are the caves. Water from oceans to tiny droplets has created and shaped Carlsbad Cavern. The rocks in which the cavern formed are the product of an ancient reef that flourished 250 million years ago.
For millions of years as the entire region subsided, the reef grew upward and outward, maintaining a height just below sea level. Eventually the reef was hundreds of feet thick and one to four miles across. Behind the reef, on the tidal flats and in the lagoon behind them, limestone and occasional sandstone sheets were deposited at about the same rate the reef was growing. On the seaward side, chunks of limestone broke away and tumbled down from the steep seaward face of the growing reef.
These broken pieces of rock formed an underwater talus slope or rubble pile. The upper level of Carlsbad Cavern is in the thin layered back reef and tidal flat deposits, while the large chambers and lower levels are in the reef and reef talus deposits. Eventually the channels supplying water from the ocean slowly closed, and the sea began to dry up. The water evaporated more rapidly than it was replaced. Salts and gypsum were precipitated and filled the basin, in time the basin was no more - the landscape was a nearly flat surface, with little relief. As eons passed, the old sea basin, the reef, and the surrounding regions were deeply buried under additional thousands of feet of sediments. Starting with its burial and continuing as movement began to occur in more recent times fractures developed in the old reef and overlying deposits. As the Guadalupe Mountains were first raised by compressive earth movements (20-40 million years ago), fresh water filled some of the fractures. Fresh ground water mixed with briney waters...
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