How are caves decorated? Why are speleothems useful?

As water passes through limestone, it Speleothems are not only beautiful, dissolves away calcite, a portion of they’re useful, too. Examining the the calcium carbonate rock, and location of speleothems within a cave Flowstone carries it in solution. When a super- can help explain how the cave saturated water droplet impacts the formed. A tight cluster of soda cave floor or simply evaporates, the straws on the cave ceiling can calcite previously held in solution is indicate diffuse flow—where water deposited in formations called passes through the rock. A long, speleothems. sinuous drapery hints at fracture flow—when water flows through There are several types of Stalagmite cracks in the rock. Even the color speleothems. Flowstone forms as and composition of the speleothems water flows over walls, floors, or can be informative. It suggests what other formations and builds up sheets types of rocks and minerals exist of calcite that look like a rock along the recharge flow path. waterfall. Stalagmites rise upward from the floor of the cave passage and As the speleothems grow, they record are usually formed by water dripping Stalactite atmospheric information such as from ceiling formations. Stalactites climatic conditions and ocean levels. hang from the cave ceiling and form Scientists at the University of Texas as water flows down the formation have found speleothems in central and evaoporates leaving layers of Texas caves that are more than calcite. When a stalactite and a 350,000 years old (Musgrove, 2000). stalagmite join they form a column. Growth rates are hypothesized to Column correlate to rainfall: the more rainfall In general, all ceiling formations are the faster the formations grow. By stalactites, but because there are so examining growth rates scientists are many distinctive types, there are more able to reconstruct regional climactic specific terms. For instance, a conditions and determine precisely drapery develops when water when they occurred (Musgrove et al., deposits calcite in thin sheets that 2001). Drapery hang in delicate folds like a curtain. References The tiny, hollow stalactites known as Musgrove, M., 2000, Temporal Links Between soda straws are particularly Climate and Hydrology: Insights from fascinating. They grow as water runs Central Texas Cave Deposits and Groundwater, unpublished Ph.D. down inside them and deposits a ring Dissertation, University of Texas, Austin, of calcite at the tip. Helectites, or TX, 432p. delicate, twisted speleothems, form as Musgrove, M., Banner, J.L., Mack, L.E., Combs, Soda Straw D.M., James, E.W., Cheng, H., and Edwards, air movement within particularly R.L., 2001, Geochronology of late humid cave passages causes the Pleistocene to Holocene speleothems from calcite formations to project at all central Texas: implications for regional paleoclimate: Geological Society of America angles from ceiling walls and the Bulletin, v. 113(12), p. 1532-1543. floor of caves.

Helectite