NR-1 Sinkhole interest, as sinkholes are generally believed to form only in environments which are subaerial, or exposed to the air. In contrast, the NR-1 Sinkhole is believed to be too deep underwater for the area to have been exposed to the air during formation in the Neogene. It was the first documented evidence suggesting that it is possible for karst sinkholes to form entirely underwater. NR-1 Sinkhole The NR-1 Sinkhole is a giant underwater sinkhole located in the Straits of Florida southwest of Key West, Florida. It is found at an approximate depth of of water at the foot of the
Devil's Sinkhole State Natural Area Devil's Sinkhole State Natural Area Devil's Sinkhole State Natural Area is a natural bat habitat near the city of Rocksprings in Edwards County in the U.S. state of Texas. Home to the Mexican free-tailed bat, access to the area is available only through advanced reservations. The Devil's Sinkhole is a vertical natural bat habitat. The opening drops down to reveal a cavern some below. The cavern was first discovered by local residents in 1876. H. S. Barber carved his name inside the cave in 1889. The area was transferred to the state of Texas in 1985, and open to the