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The Study of Caves
The study of all aspects of caves including their exploration is called Speleology. Visiting or exploring caves for recreation is called by those who do so: Caving, Potholing and/or Spelunking.
Further, the formation and development of caves is known as Speleogenesis and is a process which can occur over the course of millions of years and come about by various geological processes. These geological processes may include a combination of chemical processes, erosion by water, tectonic forces, microorganisms, pressure and atmospheric influences. Most caves are formed in limestone by dissolution of the rock by water flow.
Most caves are formed in limestone by dissolution of the rock by water flow and which are classified as being active or a relict. An active cave would still have water flowing through them, relict caves do not have water flow, even if there are areas of water retention.
Active caves are classified into
(1) inflow caves, those which a stream flows and/or descends into,
(2) outflow caves, those which a stream flows and/or emerges from, and
(3) through caves, those which are traversed by a stream.
The Types of Caves
Glacier caves are formed by melting ice and flowing water within or under glaciers. Most glacier caves are created by water flowing through or under a glacier. The water commonly originates on the surface of the glacier from melting and then enters through a moulin, a circular, vertical shaft formed from a surface meltstream eeploits a weakness in the ice and exits the glacier at the snout at base level.
Some glacier caves are formed by geothermal heat form volcanic vents or hot springs beneath the glacier ice. This type of glacier cave is subject to complete collapse or even elimination by glacial retreat. An example of the dynamic nature of glacier caves is the former Paradise Ice Caves, located on Mount Rainier.
The cavities are influenced by the very slow flow of the ice, which ten to collapse the caves again.
Any and all cavities that are formed within glacier ice are called glacier caves. However, often, ice is found in other types of caves, thus, influencing some individuals to call such caves Ice Caves.
In this context, the expression Ice Cave is any type of natural cave that contains significant amounts of perennial or year round ice. For this to happen, at least a portion of the cave must have a temperature of below 32 °F all year round and water must have traveled into the cold zone of the cave to form ice.
In most of the world, bedrock caves are thermally insulated from the surface and so assume a near constant temperature approximating the annual average temperature at the surface. However, many ice caves exist in temperate climates and due to cold traps, certain cave configurations allow seasonal convection to import cold air from the surface in winter, but not warm air during the summer.
Ice Cave include:
Bandera Volcano Ice Cave, New Mexico
Bixby State Preserve, Iowa
Coudersport Ice Mine, Pennsylvania
Decorah Ice Cave State Preserve, Iowa
Ice Mountain, West Virginia
Niter Ice Cave, Idaho
Sam′s Point Preserve, New York
Shawangunk Ridge, New York
Karst Caves, also referred to as Solution caves are the most common type of cave and forms in rock which is soluble, primarily in limestone even though some form in other rocks including chalk, dolomite, marble, salt, and gypsum. In Karst caves, rock is dissolved by natural acid in the groundwater which seeps through bedding planes, cracks, faults, joints and other such features that exist sub surface. In a matter of time, often millions of years, the water seeping through these cracks turn these small spaces into caves and cave systems.
The largest Karst caves are found in limestone, which dissolves somewhat rapidly under the action of rainwater charged with carbonic acid and other naturally occurring organic acids. This dissolution process produces a distinctive cave landform know as karst, characterized by sinkholes and underground drainage. The portion of a karst cave that is below the water table (the local level of the groundwater) will be flooded.
Cave Formations
Limestone Karst caves are often adorned with calcium carbonate formations from the slow precipitation. Types of formations, which are secondary minerial deposits in caves called Speleothems include; columns, draperies, flowstones, helictites, soda straws, stalactites, and stalagmites.
Variation of Cave Type
There is another type of solutional cave, that is those formed by a hydrogen sulfide solution, caused by hydrogen sulfide gas rising from below, where reservoirs of oil give off sulfurous fumes. When this gas mixes with groundwater and forms sulfuric acid, this solution then dissolves the lime stone from below rather than from above. Lechuguilla Cave in New Mexico and nearby Carlsbad Cavern are examples of this type of solutional cave.
Fracture Caves are formed when layers of more soluble minerals, such as gypsum, dissolve out from between layers of less soluble rocks. These rocks fracture and collapse in blocks of stone.
A volcanic cave, also know as a primary cave is one that is formed volcanic activity and the lava tube is the most common type of primary caves. As lave flows downhill, its surface cools and solidifies. However, hot liquid lava will continue to flow beneath the surface crust and if most all of the lava flows out of this conduit, a hollow tube will remain.
Lava Tubes
Volcanic caves include but are not limited to lava tubes. Other types of lava caves formed from volcanic activity include; lava rifts, lava molds, open vertical conduits, inflationary caves, blisters caves, pressure ridge caves, spatter cone chambers and a few others.
Littoral Caves
Sea caves are found along coasts around the world and a special case is Littoral caves, which are formed by wave action in zones of weakness in sea cliffs. Often these weaknesses are faults, but they may also be bedding-plane contacts or dykes.
Some wave-cut caves are now above sea level due to a subsequent uplift of the land. Elsewhere, in places such as the Phang Nga Bay in Thiland, solutional caves have been flooded by the sea and are now subject to littoral erosion.
Sea caves are generally around 16 to 170 feet in length, but may some sea caves may exist of nearly 1000 feet in length.
Anchialine Caves
Anchialine caves are those which are usually coastal containing a mixture of freshwater and saline water (usually sea water). This type of cave has a landlocked body of water with a subterranean connection to the ocean.
These sea caves often contain highly specialized and endemic fauna.
Anchialine systems are a feature of coastal aquifers which are density stratified, with water near the surface being fresh or brackish, and saline water intruding from the coast at depth.
Talus caves are formed by opening in and among large boulders that have fallen down into a random heap, often a the base of a cliff and have accumulated through periodic rockfall. The landform associated with these materials are often called talus deposits or screee and such deposits may be subject to frequent rockfalls and landslides.
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