In geography, an abîme is a vertical shaft in karst terrain that may be very deep and usually opens into a network of subterranean passages. The term is borrowed from French, where it means abyss or chasm.
What is an Abîme
Formation of an Abîme
Abîmes are a structure which form late in the life of a limestone cave. They can be 1–10 metres in diameter and up to 50 metres in height vertically. The walls have grooves that serve as a contrast to the smooth nature of the rest of the cave. They are known to lie under heads of stream valleys, sinkholes, or along non-carbonated rocks. Water will occasionally fall down the shaft, creating subterranean waterfalls. Only a small portion of the abîme connects to the rest of the cavern. They can extend to the present water table, while the rest of the cavern lies above it.
Other names
Abîme are also known as pit caves in the U.S. and pot caves in England. They can also be called domepits, due to the way that looking up from below a dome can be seen and looking down from above a pit is seen. Blue holes are sinkholes that have filled with water and can occur on land or at sea. In Central America, they are called cenotes.
Fauna
Invertebrates
Millipede
# Can live anywhere in a cave, including on the steep sides of the abîme
# They feed on humus and fungi
# They have less body pigment, thinner shells, longer legs and antennae, fewer eye facets, and longer sensory bristles than their land-dwelling cousins
Glowworms
# Live on walls and ceilings but can live anywhere inside or outside the cave.
# They can control the amount of bioluminescence they release and can glow for 24 hours a day
# They use long strings of sticky silk like material as “fishing lines” to capture small bugs
Cave Beetles
# There are 200+ known species of cave beetles.
# They are blind and have no optic nerve along with long appendages and powerful jaws.
# They feed on millipedes, other cave beetles, insects and larvae, along with guano and bat carcasses
# Cave beetles are considered troglobites since they live in entire darkness though, they may be seen on the abîme sides
# These crickets migrate between caves and the outside and feed on cave beetles
Other species
# Spiders
# Mites
# Ticks
Wintering animals
# Moths, wasps and ichneumon flies use the areas as wintering ground
Vertebrates
Snakes
These snakes do not normally live in caves but can be found at the entrances to abîmes
Snakes do occasionally fall into sinkholes caused by abîmes
One species of snake uses caves as a hunting ground for bats
Bats
Bats use abîmes as an area to enter and leave caves.
They feed the invertebrates with their guano and carcasses
Birds
Birds will use the walls as nesting roosts
Examples being cliff swallows, cave swallows, etc.
Recreation
Rappelling (A.K.A. Pit Caving)
This is the act of using ropes, harnesses and ladders to descend an abîme. This is the most popular activity besides the actual exploration of caves. It is also the most dangerous activity to do in a cave. The biggest danger comes from using poor ropes and ladders for rappelling down shafts. Many amateurs make this mistake and it leads to the most cave deaths.
Base cave jumping (Cave of Swallows, Mexico)
An extreme sport and requiring a person to stand at the entrance of an abîme and jump into the opening while pulling a parachute before hitting the cave floor. This is highly dangerous and should only be undertaken by those with experience. The Cave of Swallows is the most popular due to its 333 m. freefall drop, which is the longest in the Western hemisphere.
