Depositional Features

In the open air of the cave, some of the water may evaporate from the carbonate rich solution and increases the concentration of dissolved bicarbonate.  Eventually, it becomes saturated and carbonate begins to precipitate. Alternately, the CO2 dissolved in water can come out of solution increasing the pH of water. Either or both of these processes cause previously disolved carbonates to precipitate on surfaces and to build up limestone deposits. The material deposited by ground water is called travertine or more informally, dripstone.  Cave features or formations that are formed from dripstone accumulations are called speleothems that may grow as much as 1 cm/year under favorable conditions.

If the water in the pools is constantly agitated, as from drips, cave pearls begin to form as carbonates precipitate on limestone particles in the pool, which act as seed grains. The constant motion of the water in the pool prevents the "pearl" from attaching to the sides of the pool but not from growing as additional travertine layers are added to its surface by precipitation.

They are as varied and unique in their expression as caves are. Some of the more common speleothems are:

Stalactites

Stalactites

stalactites (hanging from the ceiling like icicles);

Stalagmites

Stalagmites

stalagmites, generally blunter than stalactites and rising from the floor;

Columns

Columns

columns, which form when stalactites and stalagmites grow together;

Soda Straws

Soda Straws

soda straws, thin, hollow stalactites from which probably all stalactites form originally;

Helictites

Helictites

helictites where the water passes through the center by capillary action rather than gravity flow. Consequently helictites look like twigs and can grow in any direction.

Cave Popcorn

cave popcorn forms from travertine precipitating as water moves to the surface of a speleothem and evaporates from small openings.

Draperies

Draperies

drip curtains or draperies form as water comes through a crack or joint and forms a linear curtain of stalactites;

Rimstone

Rimstone

Along the edges of pools, rimstone will form as water evaporates; it may also form along the edges of stalagmites within the pool and create pedestals.

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