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What is a cave?
An underground cavity that is normally formed by water dissolving the rock. Most caves are formed in limestone, but other host rocks include sandstone, granite, ice, volcanic tuff & basalt, marble & dolomite, and even mud.
What types of caves are there?
Classic Limestone Caves, Talus Caves, Sea Caves, Mud Caves, Ice Caves, Lava Tubes.
How are Limestone Caves formed?
Most Limestone caves are formed by slightly acidic water dissolving the limestone. There are lots of variations on how this happens. One scenario starts as rainwater falling from the sky and picking up carbon dioxide from the air and soil and then working it's way into the ground. This slightly acidic water begins dissolving the limestone along cracks and fissures as it works it's way down to the water table. This is one reason why many caves follow linear trends. Often these linear passages will intersect perpendicular passages and end up forming a grid pattern.
Sometimes the volume of water going into the ground is large enough to carry sediment that will mechanically enlarge the cave passage. An example of this would be the series of river caves in Belize called Caves Branch.
Some other caves are "kind of" formed from the bottom up. These caves start with Hydrogen Sulfide gases working thier way up from deep oil deposits. When the gas intersects the water table it mixes and makes a sulfuric acid that readily dissolves the surrounding limestone. A biproduct of this reaction is gypsum deposits. Large caves such as Carlsbad Caverns have formed in this manner.
How are Talus Caves formed?
Talus caves are made up of piles of large granite (or other hard rock) boulders that have active streams running underneath them. The water will wash away dirt and small rocks surrounding the boulders and leave empty cavities around the boulders. Usually the streams are running down a steep valley that helps hold the large boulders in place. Some Talus caves have boulders overlying a vertical joint that channels the water down the valley. Given enough time and water these vertical joints will be widened large enough so that the actual cave will be inside the joint. Talus caves above the bedrock joint are normally very mazey, as their passages meander around all of the boulders. Talus cave passages that lie in the joint of the bedrock are generally very straight with nearly perpendicular intersections of passages.
Talus Cave passageways generally follow a stream way, with small pools and waterfalls. The edges of the water are often coated with travertine (Calcium) that is deposited from the water. The granite boulders in the stream way are normally rounded and polished smooth, this is called spherical weathering. Rocks on the edge of the passages are rougher and often more rectangular. The cave passages in the joint layer are often vertical parallel walls such as smooth, polished granite.
How are Sea Caves formed?
Sea caves are cut into the coastal sandstone though tidal action. Most of these caves are also formed by widening of joints in the rock. Often these caves will also have sections that are wide and low. These sections are generally formed along the horizontal intersection of two different type of rock. Many sea caves are filled and emptied of sand with the changing ocean currents, as well as storms and human intervention.
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Longest Cave
Mammoth Cave
Kentucky, USA
367 Miles
590629 Meters
Deepest Cave
Krubera Cave
Gagra, Abkhazia
7080 Feet
2158 Meters
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