Calcite Crystal Deposits
Features such as stalagmites are technically called Speleothems. The word “Speleothem” is derived from the Greek words “spelaion” (cave) and “thema” (deposit). The process by which Speleothems are formed is the reverse of that by which limestone is dissolved to produce caves.
Speleothems consist mainly of calcite, the same mineral that makes up limestone, in its crystallized form.
Conditions are right for the process to begin when the water table lowers and air enters the cave. Calcite is dissolved from the limestone above the cave by slightly acidic water as it percolates downward through the soil.
In the soil, where plant and animal remains are decaying, the carbon dioxide content is about 300 times that of the outside atmosphere. The carbon dioxide combines with the water and produces carbonic acid, which in turn dissolves some of the limestone it passes through as it moves downward toward the cave. When the acidic water reaches the cave, the carbon dioxide is released and calcite is precipitated (redeposited) on cave walls, ceilings and floors.
Speleothems form at varying rates as calcite crystals build up, one upon the other. Several factors can determine the rate of growth. Two important factors are the temperature outside, which affects the rate plants and animals decay(amount of carbon dioxide in the soil), and the amount of rainfall. The shape of Speleothems is determined by how the acidic water enters the cave (by dripping, seeping or splashing) and how the water stands or flows after entering the cave. Stalactites are the most common Speleothems.
*Please note: This is an excerpt from the Cave and Karst Curriculum and Resource Guide.
A Non-renewable Resource
Great care must be taken to protect and preserve these great underground wonders. Caves are non-renewable natural resources which benefit and enrich our lives in many ways, a few of which are:
Insect Control, Scientific Knowledge, Water Supply and Education/Recreation. Caves may seem eternal, having been around for hundreds of thousands or even millions of years. However, every cave is sensitive, whether open to the public as a show cave or an undeveloped wild cave. The biggest threat to these fragile environments is man. This threat includes, but is not limited to, Vandalism, Quarrying, Dam Construction and Water Pollution.
Caves and the land in which they are located are closely tied together. What happens on the surface can affect the subsurface, including groundwater and caves. For many years it was generally believed soil protected groundwater from contamination by human activities on the surface, filtering out the contaminants. However, this was found to be untrue. Activities on the land’s surface – including sewage pollution, solid waste pollution, oil and gas pollution, and runoff from agricultural chemicals can adversely affect the quality of groundwater, which is the drinking water for about 50% of the US population.
Due to its complex geological history, New York has four types of aquifers. Those in carbonate rock are located in the valleys of central and southeastern NY. In the caves, solution channels and sinkholes (karst terrain) of these aquifers can store large amounts of groundwater. Contaminants from the surface can move rather quickly and reappear in water supplies miles from their source.
Touring a cavern gives us a good picture of karst. Imagine you are actually inside the groundwater system, touring a portion of an aquifer, where all the cracks and crevices were once completely filled with water. As the limestone beneath the soil was dissolved to form the cave, the overlying soil settled or collapsed to form sinkholes. Water entering the ground through sinkholes can carry soil, organic debris, and pollutants. This surface water becomes part of the groundwater flow system.
Contaminated water draining through a sinkhole in turn pollutes groundwater that wells and springs draw from. Sinkholes are environmentally sensitive areas and should never be used as dump sites. Sinkholes which have been used as dumps should be cleaned out to prevent any further contamination of the groundwater. Treat sinkholes with care. Remember: what you see in a sinkhole is what you may get from your faucet.
Bats Down Here?
With the exception of a few bats near the natural entrance, moss growing around the electric lights, and bacteria in the underground stream, there is little animal or plant life in Howe Caverns.
However, in many caves the food cycle approaches what is known as a closed ecologic system. In a completely closed system, every organism feeds on and is eventually fed upon by still other organisms within the system. Even though the cave environment shows a higher degree of efficiency than most, cave animals still need help from the outside to survive. All life depends on sunlight even in the darkest areas of a cave. In sunlight, green plants make food. Leaves, twigs and plant debris are carried into the cave by rainwater. Droppings (from animals that go outside the cave to feed then return to the cave to rest, such as bats) add to this organic debris. Inside the cave, bacteria and fungi decompose these materials into simple foods and nutrients.
Fungus-eating creatures such as flatworms, isopods and other small animals within the cave system feed on the molds and bacteria. These animals then become food for the larger predators in the cave, including salamanders, crayfish and blind cave fish. As the larger animals die, decay sets in and organic material is then returned to the cave environment. The entire food chain process begins again. All species in the cave system are dependent upon each other for survival. Remember, the number of animals in a cave is far fewer than their relatives on the surface. For these reasons, we must remember not to disturb life within a cave.