Caves are natural holes leading cavers deep underground to discover the unknown at each turn of their passages. The ones formed in limestone by dissolution are called solution caves. Typically, caves are dissolved while they are below the water table. It is only after a cave is drained and exposed to air that the deposition of secondary mineral features or speleothems may begin.
Water flowing through caves carves them, giving them different shapes over thousands if not millions of years. Studying their shapes help us understand the history of their formation, giving us clues on how water made its way through them, creating new passages and abandoning others.
To explore caves, one might have to go through several obstacles inherent to this activity, leaving no room for the unprepared explorer. Caving involves challenging yourself in a dark, wet and muddy environment, sometime crawling or squeezing your body through some cracks or tight tubes in the rock, or going down and up some pits using single rope techniques developed especially for this purpose. Water is often what you follow to find the way on toward the deepest portion of a cave, making you walk or swim in it despite your desire to stay dry as long as possible to avoid getting too cold.
Beside the adventure of caving that is by itself very rewarding, cavers go in caves to contemplate fragile speleothems and cave life forms, and also take the time to map them. For the latter, they use measuring tapes, compasses and clinometers to take some measurements, and they report their data and sketches in books of waterproof paper. Back on the surface, they put together their data to draw some maps that will allow them to better understand the caves and how they relate to each other and to the surface.
The caver's motto is "Take nothing but pictures, cave softly, and leave no trace of your visit."
http://www.goodearthgraphics.com/virtcave/
http://www.caves.org
http://www.cavepics.com/index.html
