- Also called:
- cavern
- Key People:
- René Jeannel
- Related Topics:
- gypsum flower
- tectonic cave
- talus cave
- solution cave
- rock shelter
cave
-
What is a cave?
A cave is a natural void in the ground that is large enough for a human to enter. Caves are formed in various rock types through a variety of processes. The most common caves are solution caves, which are created by a chemical reaction between circulating groundwater and bedrock made of limestone or dolomite. These are a component of karst terrain, a landscape with bare rock ledges and sinkholes. Other types of caves include volcanic caves, sea caves, and tectonic caves.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do most caves form in nature?
Caves form through various natural processes, with the most common being the dissolution of limestone or dolomite by weak acids in groundwater. This chemical action gradually creates sizable passages along fractures in the bedrock. Other types of caves include volcanic caves, formed in lava, and sea caves, created by wave action. Eolian caves are scoured by wind, while tectonic caves result from bedrock movement. Glacial caves are formed by melting ice, and talus caves develop between boulders.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What types of rock are caves usually found in?
Caves can be found in various types of rock, with the most common being solution caves formed in limestone or dolomite. These rocks dissolve through a chemical reaction with circulating groundwater.
Gypsum and salt are other, less common, rock types in which caves can form. Additionally, volcanic caves develop in lava, while sea caves are a product of wave action. Eolian caves are scoured by wind, and talus caves form between boulders.
1 Britannica SourceCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What are stalactites and stalagmites, and how do they develop in caves?
Stalactites and stalagmites are mineral formations found in caves, typically made of calcite (calcium carbonate). Stalactites hang from the ceiling like icicles, while stalagmites rise from the floor. They develop from slowly dripping water that carries dissolved minerals.
Stalactites form as water emerges from a crack in the cave ceiling, leaving behind a ring of calcium carbonate. Over time, this creates a tube with a central canal. Stalagmites are created as the mineral-rich water drips onto the floor, depositing additional mineral matter. The water that creates stalagmites does not always originate from a stalactite directly above it. Given enough time, stalactites and stalagmites may connect to form a column.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How can water affect the size and shape of a cave over time?
Water shapes caves through dissolution and erosion. Slightly acidic groundwater dissolves limestone bedrock, creating underground cavities that can lead to sinkholes. Over time, water flow enlarges fractures in the rock, forming cave passages.
The shape of these passages depends on water flow. Completely flooded passages become elliptical tubes, while those with an air surface develop into canyon-shaped passages. The process of water dissolving the cave's bedrock can take tens of thousands to millions of years.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why are caves important for scientists studying geology and Earth's history?
Caves are important to scientists studying geology and Earth's history because they contain a wealth of information about past environmental conditions.
Cave formations and sediments provide several clues:
* Sedimentary deposits Caves often contain layers of clay, silt, and sand, which include magnetic particles that reveal the Earth's magnetic field at the time of deposition. By measuring the paleomagnetic record in cave sediments and correlating it with the geomagnetic polarity time scale, scientists can determine the age of the sedimentary deposits.
* Speleothems Chemical sediments in caves, such as calcite and aragonite, form speleothems like stalactites and stalagmites. The shapes and composition of these formations are determined by water movement and chemistry, and the slow crystal growth provides a stable environment for analysis.
* Scallops Small scoop-like depressions on cave walls, known as scallops, indicate the direction of water flow in passages that have been dry for extended periods. The size of scallops is inversely proportional to the flow velocity of water, serving as paleo-direction indicators and paleo-flow meters.
* Dating Paleomagnetic measurements of sediments in caves have been used to determine the age of cave passages, with some passages being millions of years old.2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
News •
cave, natural opening in the earth large enough for human exploration. Such a cavity is formed in many types of rock and by many processes. The largest and most common caves are those formed by chemical reaction between circulating groundwater and bedrock composed of limestone or dolomite. These caves, called solution caves, typically constitute a component of what is known as karst terrain. Named after the Karst region of the western Balkan Peninsula extending from Slovenia to Montenegro, karst terrain in general is characterized by a rough and jumbled landscape of bare bedrock ledges, deranged surface drainage, and sinkholes, as well as caves. It should be noted, however, that there is considerable variation among karst areas. Some may have dramatic surface landforms but few caves. By contrast, others may have extensive cave development with little surface expression; for example, the Guadalupe Mountains of New Mexico, the site of Carlsbad Caverns and various other caves, have very few surface karst features.
Karst landscapes are formed by the removal of bedrock (composed in most cases of limestone, dolomite, gypsum, or salt, but in some cases of such normally insoluble rocks as quartzite and granite) in solution through underground routes rather than through surface weathering and surface streams. As a result, much karst drainage is internal. Rainfall flows into closed depressions and down their drains. Further dissolution in the subsurface forms continuous conduits that serve as integrated drains for the rapid movement of underground water. The outlets for the water-carrying conduits often are springs of majestic size. Caves are fragments of such conduit systems, and some of them provide access to active streams. These caves may be completely water-filled; others are dry passages left behind by streams that cut to lower levels. Surface streams flowing from areas underlain by insoluble rock often sink when they reach the border of a karst region. These sinking streams form tributaries of the underground drainage system.
Cave types
Not all caves are part of karst landscapes. A substantial number of relatively small caves, called volcanic caves, are formed in lava and by the mechanical movement of bedrock. Other caves are formed in glaciers by the melting of ice. Still others are created by the erosive action of water and wind or from the debris of erosive processes; these are sea caves, eolian caves, rock shelters, and talus caves.
" height="20" alt="HEW Logo">
Glacier caves
These are long tunnels formed near the snouts of glaciers between the glacial ice and the underlying bedrock. Meltwater from the surface of a glacier drains downward through crevasses, which are enlarged to form shafts leading to the base of the glacier. Because the inlet water is slightly above the melting point of ice, it gradually melts the ice as it seeps along the base of the glacier.
Glacier caves may reach lengths of several kilometres. Mature caves of this sort are tubular conduits, often with intricately sculptured walls. Some of them have a branching pattern. The floors of glacier caves usually consist of rock. Most glacier caves can be explored only when the surface is frozen; at other times they are filled with water.
Sea caves, eolian caves, rock shelters, and talus caves
Sea caves are formed by wave action on fractures or other weaknesses in the bedrock of sea cliffs along coastlines. They may be mere crevices in the cliff or roomy chambers. Some can be entered only by boat at low tide, while others, occurring along beaches, can be walked into. A sea cave may have an opening to the surface at its rear that provides access from the top of the cliff. In some cases, the ceiling entrance serves as a blowhole from which water spouts during times of high tide or rough seas. Sea caves rarely are more than a few hundred metres long.
Eolian caves are chambers scoured by wind action. They are common in desert areas where they are formed in massive sandstone cliffs. Wind sweeping around such a cavity erodes the walls, floor, and ceiling, resulting in a bottle-shaped chamber usually of greater diameter than the entrance. Eolian caves are rarely longer than a few tens of metres.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
Rock shelters are produced by bedrock erosion in insoluble rocks. A common setting is where a resistant rock such as a sandstone overlies shale or some other relatively weak rock. Surface weathering or stream action wears away the shale, cutting it back into the hillside. The sandstone is left behind as a roof to the rock shelter. Rock shelters are minor features as caves, but many are important archaeological or historical sites.
Talus caves are openings formed between boulders piled up on mountain slopes. Most of them are very small both in length and in cross section. Some boulder piles, however, do have explorable interconnected “passages” of considerable length. Some of the largest talus caves occur among granite blocks in New York and New England, where integrated systems of passages between boulders have been mapped to lengths of several kilometres.