Our first field trip was to the Indian Echo Caverns, limestone caves that sit underneath farmland off of the Swatara creek. They are known to be first used by the Susquehannock Indians, mainly for shelter in the cool and constant 52 degree caves.
They were also visited by explorers and one man called the "Pennsylvania Hermit" lived in here for 19 years! Limestone caves are created when water tables change, like with a sink hole, and then rain water leaks down through the soil and picks up calcium carbonate. The calcium carbonate erodes the limestone (pure water doesn't do it) and then deposits itself when the water evaporates.
The result is rock formations that resemble dripping water patterns.... though it takes a very long time to form. For the snowy looking rock above, one inch takes about 4,000 years!!
There were big holes up the caves.... and also some results of human interferance. See the green mossy stuff? Toursist bring in spores on our clothes, the spores go on the rocks, and then the owners of the caves put in lights.... so the spores start growing. They employ quite a few people to come in and keep the green things out, cuz it aint natural.
The formations coming down from the ceiling are called stalactites, the ones going up are stalacmites. If the drip is consistent enough, over many years the two can grow together to form a column.
Here we are blocking a great view of the crystal lake (oh well, we are cute anyway.) 51 couples have actually come down here and gotten married... if you want to be the 52nd, go on at http://www.indianechocaverns.com/index.htm. Cheers!!