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Several types of cave formations, or speleothems, are present in the Mammoth Cave system, including stalactites, stalagmites, and gypsum flowers. Stalactites are formed as water drips through a crack in the cave ceiling and leaves a small amount of calcite behind. Over a long amount of time, this calcite builds up and forms a hollow tube, with water flowing through the hollow center before dripping down. As this tube grows, water eventually begins to flow down the outside, leading to the cone-shaped stalactites, which hang from the cave ceiling and have become iconic features of caves including Mammoth.
“Mammoth Cave National Park” by Flickr user Navin75 is licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.
Similarly, stalagmites are formed as this water drips to the floor of the cave, and again deposits a small amount of calcite. This calcite then builds up, slowly forming stalagmites, which rise from the floor of the cave.
“Gypsum in the Mammoth Cave System” is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
Gypsum Flowers are another type of cave formation, and one which is very different from those previously discussed. Although it is not yet fully understood exactly how these unique features are created, they tend to form in dry parts of the cave, likely as a result of carbon dioxide and sulfur combining during the formation of the cave.
“Frozen Niagara” by Panoramio user hakkun is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
Because Mammoth Cave is a predominantly dry cave, much of it is devoid of many of these features. However, some areas of the cave, including the area known as Frozen Niagra, represent areas where the sandstone caprock preventing the permeation of water is cracked, allowing stalactites, stalagmites, and other features to grow.