How
are Caves Formed?How
are Caves Formed?
Caves are naturally formed underground passages and rooms. They can be so small that you have to take your clothes off to fit through, or so large that planes could fly through them.
(Imagine your favorite multilevel mall with absolutely no light in it, with a completely uneven floor strewn in boulders the size of cars or houses. There are no people, and you have to rig ropes to connect the different levels. Now throw in some lakes and waterfalls and weird rock formations. You and your friends have lights and food and one assignment: explore every nook and cranny. And try to have fun, please.)
Caves only form in a few types of rock, usually limestone, marble, or gypsum. If you know of any caves in your state or province, then one of those types of rocks is probably common in your area. (Unless those caves are lava tubes, which form as flowing volcanic lava cools.)
Caves begin as cracks in rock. Water works its way into those cracks, and slowly dissolves them out until they're large enough to crawl through. Why does the rock dissolve away? Because the groundwater is slightly acidic. It's not acidic when it falls as rain (unless you live in an area with acid rain, from air pollution). Rain is usually neutral in pH, but as it works its way down through the earth, it picks up something that turns it into a weak acid. That something is carbon dioxide (CO2), which comes from the animals (worms, beetles, etc.) and bacteria in the soil. When the CO2 mixes with the water, it forms a weak acid called carbonic acid (H2CO3). (You drink carbonic acid in your sodas, and the "fizz" is carbon dioxide.)
H2O + CO2 ----> H2CO3
water plus carbon dioxide = carbonic acid
The acidic water slowly enlarges the cracks,
following them as they bend and twist through the rock, 
carrying
the dissolved minerals away. Now you can see why caves are so crazy! The passage
can continue to grow larger and longer, and may eventually be left high and
dry when the cave stream moves to a different area. (Many caves are still partially
or completely filled with water. These caves are explored by cave divers using
scuba tanks.)
Sometimes waterfalls form in caves, creating vertical drop-offs or pits. These are explored using ropes and climbing equipment. For many cavers, these vertical shafts are the most spectacular and exciting parts of caves to explore. (For more details and crazy photos covering the excitement of cave exploring, click on "exploring caves.")
The first people to find and explore a cave get to name it anything they want, of course. Sometimes the name comes from something found in the cave or from something that happened in or around the cave. Pet Cemetary cave in California had a dead deer in it, and another cave in Sequoia National Park was found when searchers were hunting for a lost soldier. Its been called (you guessed it) Lost Soldiers Cave ever since then.
Ooooh, la! Imagine getting to find and name your own cave! (I know what you're thinking. No, you can't. It's considered tacky to name one after yourself.)
Click on "how formations grow in caves" to learn about stalagmites and other cave speleothems. You can also see a cross section view of an imaginary cave by clicking on "Virtual Cave Map," or to see some drawings of imaginary caves by students, click on "cave art."
