Devils Hole

Spring in Nye County, Nevada, United States

Devils Hole is a geologic formation located in a detached unit of Death Valley National Park and surrounded by the Ash Meadows National Wildlife Refuge, in Nye County, Nevada, in the Southwestern United States. Devils Hole is habitat for the only naturally occurring population of the endangered Devils Hole pupfish (Cyprinodon diabolis). The unit is part of the Ash Meadows complex, an area of desert uplands and spring fed oases that was designated as a National Wildlife Refuge in 1984.

Devils Hole is a geothermal pool within a limestone cavern in the Amargosa Desert in the Amargosa Valley of Nevada, east over the Amargosa Range and Funeral Mountains from Death Valley. It is at an elevation of above sea level and the water is a constant temperature of whose bottom has never been mapped. The pool has frequently experienced seiche activity due to far away earthquakes in Japan, Indonesia, Mexico, and Chile, which have been likened to extremely small scale tsunamis. Below the surface pool, Devils Hole descends approximately 160 feet (49 m) through what is termed the "main chamber" before reaching a narrow opening referred to as the 'funnel'. Through this opening lies a much larger chamber of the cavern system known as Acree's Chasm. Acree's Chasm is approximately 300 feet (91 m) in length, 40 feet (12 m) in width, and has a bottom approximately 260 feet (79 m) below the surface. Immediately after passing the funnel into Acree's Chamber, a narrow side tube can be found to a diver's left. This side tube proceeds approximately 90 feet (27 m) upward to a chamber with an air pocket, named Brown's Room. The tube leading to Brown's Room has at least 2 offshoots, the higher of which leads to a dead end filled with a small air pocket, and the lower of which joins with additional tubes descending from Brown's Room. Later efforts by five divers to find their bodies were unsuccessful. On June 20, 1965, during the second dive of a rescue and then body recovery mission, Jim Houtz with his dive partner dropped a weighted depth line to a depth of 932 feet (284 m) from the start of this opening, without hitting the bottom of the chamber below. Due to the strong current, the small size of the entrance, and the unknown depth of the cavern below, which Houtz termed the "Infinity Room", Jim and his partner chose not to explore this Infinity Room. This mission did, however, confirm that the Infinity Room of Devil's Hole, and the cavern system itself, has a depth of at least 1247 feet (380 m) from the surface. In March 2017, underwater cinematographer Jonathan Bird received permission to assist scientists in a four day expedition to take water and calcite core samples. The IMAX footage was included in the 2020 film Ancient Caves and extra footage was used to create the video documentary
There had been similar studies in Devil's Hole, but these are no longer permitted due to the endangered status of the Devils Hole pupfish. On September 19, 2022, a seiche reaching 4 feet (1 m) occurred at Devils Hole after a 7.6 magnitude earthquake hit western Mexico, about 1500 mile (2414 km) away. Seiches were also observed in the cave after powerful earthquakes in 2012, 2018 and 2019.

Located 650 feet (198 m) north of Devils Hole is a separate cave system called Devils Hole Cave (#2). It was first explored underwater to a depth of 70 feet (21 m) by divers from the Southwestern Speleological Society in February 1961. It had been described as being shaped like a boot with fallen rock restriction at the 50 feet (15 m) level leading to a narrow pool of water.

Devils Hole is the only natural habitat of the Devils Hole pupfish, which survives despite the hot, oxygen poor water. Devils Hole "may be the smallest habitat in the world containing the entire population of a vertebrate species". The pupfish has been described as the world's rarest fish, with a population of 263 as of 2022. Genetic information indicates that the pupfish species is as old as the Hole itself, which opened to the surface about 60,000 years ago. The pupfish have been protected since being declared an endangered species in 1967. Conflicts of the ownership and use of the groundwater around Devils Hole caused litigation in the 1980s. The litigation triggered further protections of the pupfish. Since the late 1990s, the pupfish population has substantially decreased. The reasons for the decrease are unknown, but is possibly due to a microscopic non indigenous diving beetle that is consuming pupfish eggs.