Inside Mother Earth: The Caving Experience

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WHAT YOU'LL FIND

What you'll see when you enter the earth will vary with the type of cave you're in and the characteristics of your region of the country. Nearly 95% of the world's caverns are "solution caves", which are hollowed out of limestone or a few other types of rock by the action of weakly acidic rainwater. Over time, as the water seeks the lowest point, the water table drops, leaving the resulting chambers.

Formations in limestone caves are deposits built up by calcium carbonate, which leaches downward out of the rock layer above the cave. Stalactites may form from the ceiling, while directly below them stalagmites grow from the ground. In time, these formations may join together into columns.

Other common solution-cave speleothems include flowstone (formed by water dripping down a sloping wall), bacon (thin sheets of banded flowstone on the walls or ceiling), rimstone pools, helictites (tiny shoots of calcite growing in all directions), soda straws (extremely fragile hollow stalactite tubes), moonmilk (an unusual free-form deposit), anthodites (quill-like flowers of aragonite or calcite), and gypsum flowers and needles.

Nonsolution caves include glacier caves (created by streamflow and evaporation), lava tubes (formed when surface lava cools faster than interior lava, they often have beautiful ice formations), sea caves (formed by the erosive action of sea waves), and boulder or talus caves (voids in blocks of rock at the base of cliffs) . . . as well as various "near caves" such as shallow sandstone shelters.

The number of caves in the United States is not known, but the NSS estimates that there are more than 50,000 limestone caverns alone. Although the majority of these are located in the eastern and central sections of the country, underground wilderness exists in every region.

Just as there is no single type of cave, there's also no such thing as a "typical" cave. However, it's certain that most are a far cry from their popular image as vast, dramatic caverns. Instead, they're predominantly small, low-ceilinged, wet, and muddy. And though each one reveals a unique view of the underground wilderness, all caves do share some characteristics.

Darkness is the most obvious trait, of course. Whereas our eyes are capable of at least limited sight even on the darkest night (allowing us to discern, for example, the outline of a hand), in the total darkness of a cave we are completely blind. In addition, caves are wet, containing active streams, pools, or at least dripping water. They're quite humid, too, with the air at or near its saturation point. And finally, these voids below our familiar living world are quiet.

All of these traits contribute to the attraction that caves hold for scientists, photographers, and spelunkers. The secrets of the harsh, dark, silent world beneath us are just beginning to be understood, and there's ample opportunity for interested cavers to help with the mapping, studying, and preserving of this fragile wilderness. Even if you aren't interested in pursuing caving as a sport, you owe it to yourself to visit one of the numerous commercial caves and make at least one venture into the earth to see the marvels hidden within.

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