A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word cave can refer to smaller openings such as sea caves, rock shelters, and grottos, that extend a relatively short distance into the rock and they are called exogene caves. Caves which extend further underground than the opening is wide are called endogene caves.
Wookey Hole Caves are a series of limestone caverns, a show cave and tourist attraction in the village of Wookey Hole on the southern edge of the Mendip Hills near Wells in Somerset, England. The River Axe flows through the cave. It is a Site of Special Scientific Interest (SSSI) for both biological and geological reasons. Wookey Hole cave is a "solutional cave", one that is formed by a process of weathering in which the natural acid in groundwater dissolves the rocks. Some water originates as rain that flows into streams on impervious rocks on the plateau before sinking at the limestone boundary into cave systems such as Swildon's Hole, Eastwater Cavern and St Cuthbert's Swallet; the rest is rain that percolates directly through the limestone. The temperature in the caves is a constant 11 °C (52 °F).
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as vrtače and shakeholes, and to openings where surface water enters into underground passages known as ponor, swallow hole or swallet. A cenote is a type of sinkhole that exposes groundwater underneath. Sink and stream sink are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock.
Luray Caverns, previously Luray Cave, is a cave just west of Luray, Virginia, United States, which has drawn many visitors since its discovery in 1878. The cavern system is adorned with speleothems such as columns, mud flows, stalactites, stalagmites, flowstone, and mirrored pools. The caverns host the Great Stalacpipe Organ, a lithophone made from solenoid-fired strikers that tap stalactites of varied sizes to produce tones similar to those of xylophones, tuning forks, or bells.
Craighead Caverns is an extensive cave system located in between Sweetwater and Madisonville, Tennessee. It is best known for containing the United States' largest and the world's second largest non-subglacial underground lake, The Lost Sea. In addition to the lake, the caverns contain an abundance of crystal clusters called anthodites, stalactites, stalagmites, and a waterfall.
The Caves of St. Louis have been important in the economic development of St. Louis, Missouri, United States. The city was built upon a complex of natural caves which were once used for the lagering of beer by early German immigrant brewers. Caves are naturally cool, which was especially attractive to brewers before the advent of refrigeration.
The Marble Arch Caves are a series of natural limestone caves located near the village of Florencecourt in County Fermanagh, Northern Ireland. The caves are named after the nearby Marble Arch, a natural limestone arch at the upstream end of Cladagh Glen under which the Cladagh River flows. The caves are formed from three rivers draining off the northern slopes of Cuilcagh mountain, which combine underground to form the Cladagh. On the surface, the river emerges from the largest karst resurgence in Ireland, and one of the largest in the United Kingdom. At 11.5 kilometres (7.1 mi) the Marble Arch Caves form the longest known cave system in Northern Ireland, and the karst is considered to be among the finest in the British Isles.
Dos Ojos is part of a flooded cave system located north of Tulum, on the Caribbean coast of the Yucatán Peninsula, in the state of Quintana Roo, Mexico. The exploration of Dos Ojos began in 1987 and still continues. The surveyed extent of the cave system is 82 kilometers (51 mi) and there are 28 known sinkhole entrances, which are locally called cenotes. In January 2018, a connection was found between Sistema Dos Ojos and Sistema Sac Actun. The smaller Dos Ojos became a part of Sac Actun, making the Sistema Sac Actun the longest known underwater cave system in the world.
Carlsbad Caverns National Park is an American national park in the Guadalupe Mountains of southeastern New Mexico. The primary attraction of the park is the show cave Carlsbad Cavern. Visitors to the cave can hike in on their own via the natural entrance or take an elevator from the visitor center.
The Grand Canyon Caverns, located just a few miles east of Peach Springs, Arizona, lie 210 feet (64 m) below ground level. They are among the largest dry caverns in the United States. Dry caverns comprise only 3% of caverns in the world. Because of the lack of water, stalagmites and stalactites are rare in the caverns.
The Lost River is a river that rises in Vernon Township, Washington County, Indiana, and discharges into the East Fork of the White River in Lost River Township, Martin County, Indiana. The river's unusual hydrology has led to two of its features being named as National Natural Landmarks.
Seneca Caverns is a show cave located in northeastern Seneca County, Ohio, USA, just outside Flat Rock. The cave is designated as a Registered Natural Landmark by the Ohio Department of Natural Resources.
The Blue Hole of Santa Rosa, or simply the Blue Hole, is a circular, bell-shaped pool or small lake located along Route 66 east of Santa Rosa, New Mexico that is a tourist attraction and swimming venue, and one of the most popular dive destinations in the US for scuba diving and training. The Blue Hole is an artesian well and cenote that was once used as a fish hatchery.
The Caves of the Tullybrack and Belmore hills are a collection of caves in southwest County Fermanagh, Northern Ireland. The region is also described as the West Fermanagh Scarplands by environmental agencies and shares many similar karst features with the nearby Marble Arch Caves Global Geopark.
The Blue River is a 57-mile-long (92 km), two-forked stream that runs through Harrison, Crawford and Washington counties in Indiana. The headwaters of the North Fork arise near Salem in Washington County and flow south, and the headwaters of the South Fork arise near New Liberty and flow southwest. The two small forks converge in Fredericksburg. From the confluence, the river flows south until it joins Ohio River in the Harrison-Crawford State Forest, just upstream from Leavenworth.
The Nidderdale Caves are a series of caves in Upper Nidderdale in North Yorkshire, England. There are two cave systems and most of the caves are in some way linked with one or the other. The smaller system is the Eglin cave system in the valley of How Stean Beck, a tributary of the River Nidd, associated with How Stean Gorge. The larger system is the Goyden cave system under the valley of the River Nidd, which flows east from Scar House Reservoir, then south, and shortly after disappears underground down several sink holes to reappear at the rising just beyond the village of Lofthouse. Cavers are able to access several sections of this system via the different entrances.
Indiana Caverns is part of the Binkley Cave system near Corydon, Indiana.
Cave diving is underwater diving in water-filled caves. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave diving and cavern diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified. Despite the risks, water-filled caves attract scuba divers, cavers, and speleologists due to their often unexplored nature, and present divers with a technical diving challenge.
