Montshire Minute: Caves

Originally aired during the week of December 23, 2002

Monday

The English artist and explorer Edward Whymper (WHIMP-er) was as fascinated by the challenge presented by big mountains. They were there to be climbed, he thought. In 1965, after six unsuccessful attempts, Whymper was the first to climb the Matterhorn after convincing himself that the steep east face wasn't as difficult as it looked. The same spirit of adventure motivates spelunkers, those explorers who are drawn to the depths of the earth to explore places where few dare tread. A great dream among cavers in this country was to discover a link between Kentucky's two huge cave systems, Flint Ridge and Mammoth. In 1972, after years of squirming on her belly through crawlways, sloshing through underground streams and climbing up shafts, Pat Crowther found the connection by squeezing through what is known as the "tight spot."

Tuesday

Caves can form in many different ways, but usually the process involves water. Mildly acidic rainwater can eat away at limestone caverns, forming cave tunnels, passages, and caverns. Ocean waves pounding against the coastline can scour out sea caves. Ice caves are formed when water flows underneath glaciers. Still other caves are formed by the swirling action at the bottom of a waterfall: the Cave of the Winds at the foot of Niagara Falls is one example. It usually takes thousands of years to form an opening big enough for people to move around inside. One exception to this very slow process of cave formation is the "lava tube" cave, which forms when molten rock flows away from volcanoes. Cool air causes the rock to harden on the outside and when the lava drains out, the tube becomes a cave.

Wednesday

Most limestone caves are formed by the slow but relentless flow of water underground. Water eventually pushes its way into cracks in the limestone. Over time the water dissolves channels and caves are formed. Sometimes this action results in spectacular underground scenery, if you happen to bring your flashlight. I'm talking about the stalactites that stick down from the roof of the cave . . . or is it stalagmites? OK, I got it . . . stalactites are mineral deposits, formed by dripping water over thousands of years, that hang down from the cave roof like icicles. Instead of evaporating, some drops of water may fall to the cave floor from the stalactite icicle. Mineral deposits may collect on the floor of the cave forming a spike called a stalagmite. Over the ages, the two structuresóone from the cave floor and one from the roofómay develop into a solid column.

Thursday

Scientists have known for a long time that caves are formed from water flow and the corrosive effects of water percolating through limestone. More recently, researchers have been exploring other extreme ways that caves are formed. Would you believe bacteria that gobble up hydrogen sulfide gas like we do bread and water? Microbes feeding on this gas excrete sulfuric acid, helping to carve out caves like the famous Carlsbad Caverns. Bacteria dissolving rock seems absurd, until you consider that these critters can live in conditions that resemble the inside of your car battery. A group of scientists that go into caves in search of these microbes consider themselves members of the SLIME club (that stands for Subsurface Life in Mineral Environments). They believe these creatures may hold clues to the earliest life on Earth, and the possibility of life in a really extreme environment - outer space.

Friday

Depending on where you are in a cave, there may be a little bit of light, or no light at all. A surprising variety of plants and animals have found ways to survive in this dim environment. Of course, bats live in caves. Some species use caves for hibernation, others call it home, leaving at regular intervals during the evening to search for food. In many cases, the excrement of bats piles up in deep deposits on the cave floor. This is called guano, a source of fertilizer. Bat guano in Mammoth Cave was used during the Civil War to make saltpeter, a nitrate used in gunpowder. Creatures that live out their lives in almost total darkness deep inside in caves include the blindfish, found in some Kentucky caverns. The fish is colorless and it has only a trace of an eye socket. With no light to see by, the blindfish has evolved highly sensitive organs on the front and sides of its head which helps it navigate.