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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 tend to collapse the caves again.
1a. Ice Caves
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 Examples:
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
A solution cave is formed by dissolving the rock by liquids. This process of a liquid dissolving solid matter only occurs under a few specific conditions. A particularly good solvent is water, which at the same time, is also the only one that occurs in nature in sufficient quantity. However, other substances can be involved in the solution, especially various types of acids.
Rocks such as salt or gypsum are directly soluble in water, and when the water occurs in very large quantities, both salt and gypsum karst develops very quickly.
Limestone is not soluble in water. However, limestone can be dissolved by carbonic acid created by carbon dioxide in meteoric water.
1 Limestone dissolution by sulphuric acid and sulphurous acid is also very important. Sulphur compounds can form these acids both chemically and biogenically. Sandstone and especially quartzite, a sandstone consisting exclusively of quartz, are not soluble under normal conditions. But high temperatures and large amounts of water or alternatively a very long time, in combination with acids in the water, also dissolve these rocks.
Solution Cave Formations
Limestone 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.
Solution Cave Variation
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.
Karst Caves, also referred to as Solution caves are the most common type of cave and form in rock which is soluble with most of this type forming 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 landform know as karst, characterized by sinkholes and underground drainage. That portion of a karst cave that is below the water table (the local level of the groundwater) will be flooded.
2b. Gypsum Caves
Gypsum caves are a natural karstic formation in deposits of gypsum or anhydrite. Gypsum karst is very rare. It depends on deposits of gypsum or anhydrite, which are also known as alabaster.
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Gypsum Cave Locations:
Cave of the Crystals in Chihuahua, Mexico
Cuevas de Sorbas in Almeria, Spain
Lechuguilla Cave in New Mexico, US
Optymistychna Cave in Ukraine, longest gypsum cave, 232 km.
Orda Cave under the Western Ural Mountains, 5.1 km length
2b. Quartzite Caves
Quartzite caves are subterranean passages formed within quartzite rock formations, known for their unique geological characteristics and microbial life. Quartzite cave formation, or speleogenesis, is a slow process involving the dissolution of silica-rich matrix and the mechanical removal of quartz grains. Quartzite caves exhibit a range of morphologies, including branchwork, anastomotic, and network patterns.
Quartzite Cave Locations:
Buraco das Araras, Goiás, Brazil
Corona ′e Sa Craba Cave, Sardinia, Italy
Gruta do Centenário, Minas Gerais, Brazil
Imawari Yeuta, Muchimuc, and Roraima Sur in South American Tepuis
Monte Cristo Cave, Southeastern Brazil
Nelson Bay Cave, Plettenberg Bay, South Africa
Sima Humboldt, Bolivar, Venezuela
Sima Martel, Bolivar, Venezuela
2c. Sandstone
Sandstone caves are natural openings in sandstone rock formations, often created by erosion from wind, water, or tectonic activity. They can vary in size and shape, from small alcoves to large caverns, and are often characterized by unique patterns and colors in the sandstone. Some sandstone caves are significant geological features, while others are important cultural sites with evidence of past human activity.
Sandstone Cave Locations:
Galiano Island Canada
Pilliga Nature Reserve, Austrailia
Sand Cave, Shawnee National Forest, Illinois
Caves of Faribault, Faribault, Minnesota
2d. Salt Caves
A salt cave is a cave formed within rock salt by the dissolution of this very soluble rock by water. As with other soluble rocks, a distinctive set of landscape features can arise from the solutional process; in this case it is known as salt karst or 'halite karst'. Often, salt caves are human made void spaces with salt deposits for the purpose of Halotheraphy, a complementary therapy that involves inhaling or being exposed to dry, finely ground salt particles.
A volcanic cave, also know as a primary cave is one that is formed by volcanic activity. The most common type of primary cave are lava tubes. As lava flows downhill, its surface cools and solidifies. However, hot liquid lava will continue to flow beneath the surface crust and when most all of the lava flows out of this conduit, a hollow tube will remain.
3a. Lava Tubes
Lava tubes are the most common volcanic cave. This process happens very often, and results in extremely huge caves. As a result lava tubes are the second most common type of caves on earth after karst caves.
During long lasting eruptions, lava flows tend to become channeled into a few main streams. Like a river they follow the geographical valley and mostly stay inside their channel. Overflow of lava from these streams solidifies quickly and supports the channel walls, building natural levees or ramparts. A solid crust can form overhead, enclosing the channel in a tube which channel is tube is created by the flowing lava itself, a self supporting process. If, when the source of the lave ceases and all the remaining lava flows out of the lava tube, the tube becomes a lava tube cave.
3b. Blister Cave
A blister cave is a very uncommon type of cave volcanic cave and is created by gas pressure that forms a bubble in the rock. Blister caves are primary caves and are also a type of lava cave because they are formed by and in lava. They are much smaller than lava tubes, although they may have a rather big diameter, because they always consist of a single blister.
The life span of a blister cave is rather short as lava begins to erode as soon as it cools down. Similar to lava tubes, they are generally completely destroyed after 20,000 years, which means there are no caves remaining in older lava streams.
The biggest blister caves are found at Mount Fantalo in Ethiopia. There are about 130 blisters are known where the still intact blisters are up to 100 feet in diameter, but other, already collapsed ones are up to 325 feet. There are only two blister caves which are currently show caves: 1. Grotte du Chien in France and 2. Musanze Cave in Rwanda. These are the only known blister caves.
3c. Lava Molds
A lava mold is a cave caused by objects which are enclosed by a lava flow. While the heat of the lava causes the object to burn, if it is wet and big enough, it will also cool down the lava surrounding it. The lava later becomes entirely solid, and when the object is burned and/or rots away, what remains is an empty mold. Later, when the volcanic eruption has ended and the lava flows away, what is left is an empty mold on the surface. If the lava does nor flow away, but instead, it solidifies around the mold, what is formed is a pit.
There is also the possibility that a fissure opens and sprays fountains of lava into the air. The falling lava coats trees and again the insides burn out leaving a lava mold around the tree. Sometimes even trees trunks lying on the ground are covered by a lava flow, the result is a horizontal tube. And if the resulting tube is big enough for a human to enter, it is called a cave.
A tree is the most common but not the only thing, which is included in the Lava Molds. Trees are often covered by a lava flow, and if they are not burnt while inside the lava they subsequently decay rather fast, leaving a negative mold of the former tree. Occasionally, the mold is large enough to crawl through, which then classifies the lava mold as a cave. In general any plant, animal or other thing which has been encased in lava, then decays rather slowly, will leave such a cave. There are numerous tree molds over the world, and there is even one cave which is thought to be the mold of a huge rhinoceros.
3d. Other Types
Other types of lava caves formed from volcanic activity include; dyke caves, lava rifts, lava molds, inflationary caves, megapillows, open vertical conduits, pressure ridge caves, spatter cone chambers and sub-crustal drainage lava caves.
4a. 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.
4b. 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.
A tectonic cave is formed by some type of ground movement.
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.
5b. Talus Caves
Talus caves are formed by opening in and among large boulders that have fallen down into a random heap, often at the base of a cliff and have accumulated through periodic rock fall. The landform associated with these materials are often called talus deposits or scree and such deposits may be subject to frequent rock falls and landslides.
5c. Neotectonic Caves
Neotectonic caves are a special form of tectonic caves that occurs almost exclusively in Scandinavia. They are created by tectonic forces in connection with the pressure relief caused by the melting of the glaciers of the ice age.
5d. Incasion Caves
Incasion Caves (or cave breakdown) is a speleological term which means any type of collapse related to the cave formation or developement caused mainly by the collapse of the roof. This process does not create caves but often transforms them substantially.
A rock shelter (also known as: rockhouse, crepuscular cave, and/or bluff shelter) is a shallow cave-like opening at the base of a bluff or cliff and are almost always modest in size and extent.
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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