CAVE FORMATION AND GEOLOGY

Basic Cave Geology for Elementary

Where Do Caves Come From?
In Caves are found a kind of rock called dolomite. It is similar to limestone. Like limestone, dolomite is formed at the bottom of the sea. Later on, forces from inside the earth pushed up the sea bottom to make the mountains. These forces, pushing up on the rock layers, cracked the dolomite, much like a baseball hitting a window cracks the glass. These cracks are called joints. This was the very start of cave forming, and it happened just as the dinosaurs started to roam the Earth.
As rainwater fell on the ground, it picked up a small amount of acid from the rotting leaves. This acid, called carbonic acid, is the same thing that gives soda pop its fizz. This acidic water can dissolve holes in dolomite. Below the water table, the rock was filled with this acidic water. Between the layers of rock and inside the joints, the water slowly dissolved away the rock. This made a large water-filled space. As the Current River cut its river valley, it cut down through the rock layers until it opened up the cave. This let the water out and gave us an air-filled cave.
How Does Water Move Underground?
Water from rainfall still moves into the cave today. A small amount seeps through the rock. This seepage gets filtered as it comes down. It is clear, but not always pure water. Most water that enters the cave comes down through the joints, which connect the cave with the surface. Where there are many joints, sinkholes can form on the surface. Sinkholes act like funnels, collecting rain water from the surface and funneling it into the cave. At some caves, joints leading down from sinkholes have become so big that people can enter the cave through the sinkholes.
Sometimes, a cave can pirate water from a surface stream. Just as a pirate took treasure away from someone else, a cave may take water away from a surface stream. If a stream crosses a joint, water may flow down the joint and into the cave. On the surface, water may be flowing down the stream, and then just disappear. This is called a losing stream. Like sinkholes, a losing stream usually means that there is a cave nearby.
All of this water that enters the cave has to go somewhere. It is no surprise that many caves have springs flowing out of them. Caves are not cut off from the rest of the world. Many have a constant flow of water moving in and out of the cave all of the time. This water carries the clay, which becomes cave mud. This is natural. Unfortunately, people have often used sinkholes for trash dumps. This means that some caves get lots of junk in them. This is bad for the people and animals that depend on the caves for their water.
1. Do you drink spring water or well water that comes from caves?

2. Do you think it is a good idea to fill sinkholes with garbage?

3. What can happen if you do?

4. How many ways can water get into caves?

Calcite Deposits or Speleothems
Remember that all this water moving into the cave carries carbonic acid. Just like sugar dissolves in water, the mineral calcite is dissolved out of the rock by the acidic water and carried down into the cave. When the water drips down into the cave, it deposits calcite on the ceiling. Each drop deposits a little ring of calcite, building a long hollow tube. These are called soda straws, because they look like the straws through which you sip a soda. This happens very slowly, often taking 100 years for a straw to grow only one inch. Once one is broken, it takes a long time to grow back.
A soda straw is the beginning of a stalactite. "Stalactite" has a "c" in it, and a stalactite is a calcite deposit that sticks tightly to the ceiling. A soda straw becomes a stalactite when the inside of the tube becomes blocked. Unable to run down the inside, water runs down the outside, depositing calcite and thickening the soda straw. The stalactite continues to grow as long as the water keeps dripping. Water that drips onto the floor of the cave also leaves calcite behind. This builds up into a stalagmite. Stalagmite" has a "g" in it, and a stalagmite is a calcite deposit that grows up from the ground. If a stalagmite gets tall enough, it might reach a stalactite. When a stalactite and a stalagmite grow together, they form a column from floor to ceiling. Stalactites, stalagmites, and columns are called dripstone because they are deposited by dripping water. Flowing water also deposits calcite, making flowstone. A flowing stream of water can even build dams of flowstone across itself. These are called rimstone dams. Scientists call all of these calcite deposits "speleothems" from Greek words meaning cave rock.

CAVE ECOLOGY

Surface / Subsurface Relationships:
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.
Groundwater pollution in cave country is a serious problem. It is often more serious than surface water pollution.
Several types of groundwater pollution occur frequently. The most common form of groundwater pollution is human waste (sewage), followed by industrial and hazardous waste. All too commonly, poorly planned sewage systems (such as septic field systems) contaminate nearby wells and springs. Entire towns may contaminate karst groundwater systems if they discharge waste water to surface streams which sink into the ground and feed groundwater supplies. Whatever the source, groundwater pollution is the result. The key to preventing these problems is sound planning which places major emphasis on the protection of groundwater quality.
If sewage enters karst groundwater systems, it can seriously deplete the amount of oxygen dissolved in the water. Without this oxygen, aquatic life will die of suffocation. When serious oxygen depletion occurs, the underground waters exude offensive odors.
Industrial waste includes everything from chemical and gasoline spills to landfills to the disposal of hazardous and radioactive wastes. The location of industrial plants is important since many factories use chemicals and other materials which can seriously degrade water quality. Factories must have good waste disposal facilities.
Gasoline and other petroleum products are very familiar to all of us. However, many of these products are very serious water pollutants. Leaking underground fuel storage tanks have ruined thousands of wells. Gasoline can readily follow the same underground routes as water. Imagine what would happen if gasoline were spilled in a sinkhole. Unfortunately, it is almost impossible to remove all of the gasoline once it enters the groundwater system.
With the nation's growth and with changes in technology have come exotic wastes. Many of these wastes are hazardous, and many of the wastes present extremely difficult disposal problems. Hazardous wastes can create particularly serious groundwater pollution problems in karst areas.
Even the disposal of common trash and garbage creates serious problems in karst areas. We generate about 1 kilo of solid waste per person per day. At present, much of this waste goes to landfills. In karst areas, substantial volumes of water commonly move through the trash and create a liquid called landfill leachate. These leachates routinely contain large concentrations of heavy metals, chemicals and toxic materials. Furthermore, landfill leachates have a tremendous demand for oxygen. When landfill leachates mix with clean groundwater supplies, they often produce septic springs and wells. Septic waters kill aquatic life and cause terrible odors.
City sewers can also cause problems for groundwater in karst areas if the sewers leak. (and they often do leak!) Sinkhole development and land subsidence are common processes in karst areas, and these processes can crack sewer lines or separate connections in the lines. Much of the sewage from the sewer lines discharges into springs.
What can we do about all of these problems? First, everyone needs to understand that wastes from our use on the surface can easily enter karst groundwater systems. Creating pollution problems is not a benefit for anyone.
Factories must be located where they are not likely to cause serious groundwater pollution problems. For example, we should avoid locations in areas with numerous sinkholes.
The storage of gasoline and other fuels must be done very carefully. Many of the newer fuel storage tanks are designed so that they are less likely to leak and so that leaks can be more easily detected. When leaks and spills do occur, clean-up efforts must begin quickly.
Many city sewers are very old and have leakage problems. These sewers need to be replaced. Sometimes old sewers can be repaired by inserting new plastic pipes inside the old sewer lines. New sewers need to be constructed of materials which can better withstand the effects of sinkhole collapse and land subsidence. When new sinkholes develop along this sewer line, this new pipe will stretch across the holes rather than break and dump sewage into the groundwater system.
Sinkholes
A good way to understand some of the relationships between the surface and the subsurface in cave areas is to discuss sinkholes. A sinkhole is a depression in the earth's surface with subsurface drainage. Sinkholes occur because solution has dissolved out a drainage network in the rock through which substantial quantities of water can pass from the surface into the subsurface.
Sinkholes connect with the underground stream system in the area. Soil, organic debris, and pollutants move underground from sinkholes during rainstorms. These materials are transported through the underground stream system (which of course passes through caves), and finally reappear on the surface again at springs.
A sinkhole is a portion of the underground stream system. A sinkhole relates to the underground stream in much the same way as a surface gully relates to a surface stream system. If we are to protect the quality of water in surface streams, we must protect the quality of water in gullies. Similarly, if we are to protect the quality of water in underground streams and springs, we must protect the quality of water entering sinkholes.
Some people even dump garbage in sinkholes! Can you think of a worse place to put your garbage?

CAVE LIFE

BIOLOGY OF CAVES - Elementary Background

Unlike the surface environment that is very changeable, cave environments are constant. It is a world of total darkness, constant temperature and high humidity. The animals that live in caves must not only adapt to these conditions, they must live in an environment where there is very little to eat. The population of animals living in caves is very small compared to the animal life on the surface. Consequently, a number of cave animals are on the endangered species list. This means that they are in danger of becoming extinct.

The Cave Food Chain

All life depends on sunlight, even in the darkest areas of a cave. No green plants grow here because they need light for photosynthesis. On the surface, green plants make food. Cave animals must depend on occasional floods to wash leaves, twigs and plant debris into the cave. Another food source is provided by droppings from animals that go outside to feed then return to the cave to sleep or raise their young. The droppings from animals, such as bats and crickets, may provide the only major food source in some caves. Few animals can directly feed on these droppings. Instead, bacteria and fungi decompose these materials into simple foods and nutrients. Fungus-eating insects, such as beetles and mites, feed on the fungi and bacteria on animal droppings and plant debris. These animals then become the food supply for the larger predators like salamanders or crayfish. The droppings from larger cave animals replenishes the food supply for fungus and bacteria. Thus the food chain continues. 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 remember NOT to DISTURB life within a cave.

Types of Cave Life
Cave animals fit into three categories based on the amount of time they actually spend in the cave.
Trogloxenes: from the Greek words "troglos" (cave) and "xenos" (guest). They are temporary cave residents which freely move in and out of the cave. These cave visitors seek out such a habitat from choice, and never complete their entire life cycle in the cave. Bats are usually the first trogloxenes that come to mind. Some species prefer the constant temporature of caves for hibernation and to bear their young. Bats, bears, skunks, moths, and people are examples of trogloxenes. Many of these animals are not dependent on the cave for their survival, they show no special adaptations to the cave environment.
Troglophiles: from the Greek words "troglos" (cave) and "phileo" (love). These cave loving animals can live in the dark zones of a cave, or they can also survive outside the cave. At times they will venture out in search of food. This group includes earthworms, some beetles, cave crickets, frogs, salamanders, and some crustaceans (such as crayfish).
Troglobites: from the Greek words "troglos" (cave) and "bios" (life). They are the true cave dwellers which spend their entire lives in the cave. Living permanently in the dark zone, these species are found only in caves and cannot survive outside the caves.
Troglobites have developed special adaptations to help them survive in caves. Since cave food sources are meager, the sense organs and physical resources of troglobites are devoted to finding food. Sense organs and physical adaptations that are beneficial to the animals’ survival are enhanced. Sense organs that are not necessary have degenerated.
Most troglobites are white to pinkish in color. They lack pigment (color) because they have no need for protection from the sun’s rays or for camouflage to hide them from predators. Many have no eyes or eyes that are poorly developed. Eyes are not necessary because of the lack of light. Since eyes require food energy to maintain, and are very prone to injury, an eyeless cave fish can survive longer with less food than a fish that has eyes.
What the troglobites have lost they make up for with longer legs and antennae, or feelers, and with adaptations that enable them to go for long periods of time with little food. Animals that have completely adapted to cave life include: cave fish, cave crayfish, cave shrimp, isopods, amphipods, millipedes, some cave salamanders and insects.

The Big Story: Bats
What animal can fly with its hands, "see" with its ears, and sleep hanging upside down? Your friendly neighborhood bat. Bats are tiny mammals that are often feared by many people. Bats are one of the most misunderstood animals. The truth is that bats are gentle, intelligent animals that are quite timid when it comes to interacting with humans.
Did you know that bats are the only true flying mammals in the world? They are one of the most numerous and diverse orders of mammals. The total world population of bats is more than ten billion. About 1,000 species are recognized. In the United States, there are over 40 species of bats working to keep mosquitoes from bugging you.
Cave bats range in size from three to five inches long, with wingspans between eight and thirteen inches. Most bats have wingspans of less than five inches. The wing of a bat is actually a hand. (Bats are of the order Chiroptera, Latin for "hand wing.") The wing is composed of the forearm and extended "fingers" of the hand. The third, fourth, and fifth fingers, or digits, of the hand support most of the wing membrane. The thumb is a tiny hook on top of the wing. The wing membrane connects with the body, back legs, and, in most bats, encloses the tail. Cave bats weigh very little, less than an ounce.
Bats can live up to 25 years and usually have only one young each year. As with other mammals, the baby bat is born alive and is fed milk by the mother. Females often nest in large colonies. They roost in caves during the day, preferring dome shaped ceilings for safety from predators. Roosting bats hang by their feet with their wings folded around them. Bats not only roost in caves, but also in attics, towers, and other man-made structures; some species even live in trees.
Many people think that bats are dirty and carry diseases. Bats are actually clean and almost disease-free animals. And yet, people are concerned that all bats carry rabies. This misconception began over forty years ago when inadequate testing procedures found that all bats tested positive for rabies. After better testing procedures were developed, it was found that bats carry a harmless virus that gave the same reaction as the rabies virus. Unfortunately, the damage was already done and this peaceful little creature was labeled as a menace to society. However, as with all mammals, there is a possibility that a bat may contract rabies but rabid bats are rare; less than one-half of one percent of bats carry rabies. Many more rabies cases can be attributed to dogs, cats and other animals than to bats. As with any wild animal, a sick or injured bat should not be handled!
You are most likely to see bats swirling around a streetlight as they devour your local mosquito population. Bats are the only major predator of night-flying inects. One gray bat may eat up to 3,000 insects in a single night! There is a colony of Mexican free-tailed bats that eats more than 250,000 pounds of insects every night! Bats feed at night, catching insects such as moths, flying beetles, and mosquitoes. How do bats manage to steer through the darkness of night and the total blackness of caves with such ease and accuracy? They use ultrasonic sound to locate insects. Bats send a high frequency sound that bounces off objects. They hear these echoes and locate, identify, and capture moving prey while flying through the dark. This process is called echolocation. Echolocation helps them navigate through the cave in total darkness. Have you ever noticed the large ears of bats? These large ears help them hear these echoes.