NR-1 Sinkhole

The NR-1 Sinkhole is a giant underwater sinkhole located in the Straits of Florida 40 miles (64 km) southwest of Key West, Florida.[1] It is found at an approximate depth of 1,886 feet (575 m) of water at the foot of the Pourtales Escarpment, an area of Quaternary sediment.[1][2] It was discovered in October 1994 during a survey conducted by the American submarine NR-1, a U.S. Navy nuclear research submarine, and is named for the submarine.[2] It was first identified via side-scan sonar and near-bottom echo sounder data, prompting a second survey in May 1995 to confirm the finding.[1]

Discovery of the NR-1 Sinkhole prompted scientific 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.[2] It was the first documented evidence suggesting that it is possible for karst sinkholes to form entirely underwater.[1][2]