Stalactites and column formations are classic features of limestone caves.
Limestone caves are formed where water leaks through cracks in limestone bedrock near the surface. Rainwater passing through rich soil and vegetation reacts with carbon dioxide to form weak carbonic acid. Over time, this weak acid dissolves the stone it runs through, creating caves deep within the bedrock. The water evaporates, leaving behind the dissolved limestone. These two natural processes--dissolution and evaporation--create the beautiful flowing rock formations, or speleothems, associated with limestone caves.
Stalactites, Stalagmites and Columns
The most commonly noted features of limestone caverns are rock projections formed by dripping rock--stalactites, which are pointed rock formations resembling teeth that hang from the ceiling of a cave, and stalagmites, which are rock formations found most commonly beneath stalactites that rise upward from the floor of the cave. When a stalactite and stalagmite grow so long they meet, they form columns. These formations are all created by water dripping through narrow cracks in the ceiling, then evaporating to leave stone behind. Stalactites by themselves are formed by slow drips. Faster drips create stalagmites.
Soda Straws and Bacon Strips
Soda-straw formations are slender, hollow stalactites created by the evaporation of carbon dioxide from water drips. When the carbon dioxide evaporates, water releases dissolved limestone in a ring around the drop. Over time, these rings build up hollow, straw-like stalactites in straight or curved shapes, sometimes even forming curls and spirals. If these stalactite formations are very close together along a crack, they may form a sheet of rock often referred to as a bacon strip.
Flowstone
Flowstone forms along cave walls where the cracks are very close to the edge. This formation is quite similar to stalactites and stalagmites, but instead of drips evaporating at the tips of formations, the entire flowstone wall is typically damp, with water evaporating from all over the stone. This formation is often remarkable for its vibrant and varied colors, caused when other minerals and metals are trapped in the water forming the stone. Stalactites and bacon strips often form draperies at the bottom of flowstone, particularly on large features. Niagara Falls in Mammoth Cave is probably the most famous flowstone formation.
Gypsum Formations
Gypsum flowers form in dry parts of caves where there is a high concentration of sulfur in the bedrock as well as calcium carbonate. The sulfur reacts with calcium carbonate to form gypsum crystal. This soft mineral "grows" on cave ceilings and walls, extruding like toothpaste into shapes that often resemble delicate flower petals. Soda straws often resemble gypsum flowers, but the two formations are very different in both composition and creation.
Tags: carbon dioxide, rock formations, calcium carbonate, dissolved limestone, features limestone, formations very, limestone caves
