The Little Sac River runs along the northeast side of the cave property, flowing through a deep valley. Once the valley was not as deep, and the river level corresponded with the upper level of the cave. During this period, the upper level of the cave was an active spring system.
But as the river eroded deeper into the valley, the water level in the cave lowered. Figure 1 is a map of Fantastic Caverns, showing portions of both levels.
Dripping water can enter a cave and deposit mineral decoration. The most common mineral is calcite (often called lime), but others such as aragonite and gypsum are found in caves. This process is similar to the buildup of minerals in a tea kettle.
The water begins as rain or snow falling on the ground. As it seeps through the soil and through cracks in the rock, it dissolves out minerals that it carries in and deposits in the cave.
Chemically speaking the process is as follows: Rainwater absorbs carbon dioxide from air and from decaying plants in the soil (the microorganisms which decay plants work the same way we do – they take in oxygen and give off carbon dioxide).
This turns the water into mild carbonic acid – kind of a weak soda water – that dissolves calcite from the limestone as it seeps down.
When the water enters the cave, it looses some of its carbon dioxide to the air, becoming a weaker acid not able to hold as much. This forces the water to deposit calcite.
Common cave formations include stalactites which grow from the ceiling (stick “tite” to the ceiling), stalagmites which grow from the floor (“mite” grow to the ceiling), and columns which join the floor and ceiling.
These formations grow from dripping water – and are collectively called dripstone. Thin sheets of water flowing down a wall or out across the floor creates flowstone.
Long Caves. Some of the longest cave systems in the world are found below the United States. The Mammoth-Flint Ridge Cave System of Kentucky has over 340 miles of interconnecting passages, making it by far the world’s longest known cave.
Some other long U.S. caves: Jewell Cave in South Dakota over 80 miles, Wind Cave in South Dakota over 60 miles, Lechuguilla Cave in New Mexico over 60 miles. The longest known caves in Missouri is Crevice Cave, south of St. Louis and not open to the public, at about 28 miles.
Deep caves. Lechuguilla Cave in New Mexico is over 1500 feet deep, making it the deepest known cave in the U.S. But unlike the long caves, the U.S. does not have the world’s deepest caves. Europe has some caves over 4000 feet deep.
Unique Caves. Carlsbad Caverns has several hundred thousand Mexican Freetail Bats, which storm out of the cave at dusk in the summer. Waitoma Cave in New Zealand contains glow worms.
Some caves are toured by boat (Spook Cave in Iowa, Penn’s Cave in Pennsylvania, and Blue Springs Caverns in Indiana), by rail (Postojna Cave in Yugoslavia), and by jeep drawn tram (Fantastic Caverns in Missouri, Harrison Cave in Barbados). Cave explorers often tour caves on their hands and knees or even on their stomachs!
CAVE PLANTS AND ANIMALS
There is no natural light in caves. Without light, no green plants can grow. Algae, moss, and sometimes-even ferns grow around lights in cave attractions, but they can grow there only because of the artificial lights.
Without green plants, what can grow in a cave? Only non-green plants such as fungi, plus bacteria, grow in the dark interior of caves. They depend upon organic material rather than photosynthesis for food.
Occasionally mushrooms grow on wood washed into caves, but bat guano generally will not support them. Mushrooms have been grown commercially in caves by hauling in horse manure or other organics.
Fungus and bacteria are crucially important to animal life in caves. Because there is no light to grow green plants for the animals to eat, the cave food chain is based upon detritus.
Detritus consists of bat guano, cricket guano, sticks, leaves, dead bats, and any other dead organic material. However, most cave animals cannot digest this detritus. instead, they eat bacteria and fungus that can consume the organic detritus.
Some cave animals are predators and eat other cave animals. Bats do all their feeding outside where they eat insects. Figure 3 illustrates the cave food chain.
Animals that spend their entire lives in caves are tiny, white and blind. The predators, such as the Ozark cavefish, the cave crayfish, and the grotto salamander, are still only a few inches long. Other cave animals are even smaller. Several hundred kinds of animals inhabit underground Missouri.
Cave animals are sparse and small because there is so little food in caves. In most Missouri caves, the amount of food is perhaps only 1/2000th of the food on the surface. Even in caves with large bat colonies, where there is more food because of bat guano, the cave has only 1/200th as much food as the surface.
Why are cave animals white and blind? Beyond the entrance area, caves have no light, so animals living there have adapted. True cave dwelling species lack skin pigment since they need neither sun protection nor camouflage.
They are albino, permanently white. In addition, some animals (such as surface fish) with skin pigment will sometimes enter caves. These animals get very light colored because their skin pigment requires sunlight to make it work.
Like pigment, eyes have no value in the total darkness of a cave, so there is no evolutionary pressure to maintain them.
In fact, an animal with eyes might injure them; eyes in a cave become a liability.
But cave animals have their other senses more keenly developed. The Ozark cavefish, for example, has receptors along the lateral line of its head and body. These receptors pick up movement in the water.
At least eight kinds of bats inhabit Missouri caves. Two kinds (or species) are the eastern pipistrelle and the grey bat. Pipistrelles are tiny bats with wings spanning only 5-6 inches and weighting five grams (the weight of a nickel). No vampire bats live in the United States. They do, however, live in Mexico and Central America.
Bats are not blind. But they do have a sophisticated sonar – if you make your living snaring mosquitoes in the dark you need to go high tech.
The sonar works like this; the bat makes a high pitched sound, and then uses the echo to “see” his surroundings.
Bats typically eat about half their body weight in bugs each night. They do the job of birds, only they work at night. Many of these bugs damage crops and forest trees.
Bats also eat mosquitoes. They supply guano (bat manure) essential for the animal life in many caves. Bats are beneficial to man; they are not to be feared or disturbed. Four species of bats in Missouri are near extinction.
Why do bats hang upside down? Probably for three reasons.
One, when bats sleep and especially when they hibernate, they lower their body temperature and slow down their respiration and all body activities. Body temperature lowers to near the cave temperature, which here in the Ozarks is about 56-60 degrees F.
When they are flying, their temperature is near 100 degrees. They could not balance like a bird under such conditions; it’s easier to hang upside down. Two, by hanging from the cave ceiling, bats are out of reach of predators.
Three, because they fly, bats are true lightweights. Their bones are thin and light for flight. In fact, engineering studies show that the femur (upper leg) won’t support the bat upright.
But by hanging, the weight is transferred from the bones as compression to the ligaments as tension. The ligaments easily hold the weight.
Are there snakes in caves? Only at the entrances. Caves are too cool for snakes; their metabolism slows down and they get sluggish. Besides, food is scarce and difficult to find in total darkness.