Ground water is a strong erosional force, as it works to dissolve away solid rock. Carbonic acid is especially good at dissolving the rock limestone. Working slowly over many years, ground water travels along small cracks. The water dissolves and carries away the solid rock gradually enlarging the cracks, eventually forming a cave.Ground water carries the dissolved minerals in solution. The minerals may then be deposited, for example, as stalagmites or stalactites.If a stalactite and stalagmite join together, they form a column. One of the wonders of visiting a cave is to witness the beauty of these amazing and strangely captivating structures. Caves also produce a beautiful rock, formed from calcium carbonate, travertine. Ground water saturated with calcium carbonate precipitates as the mineral calcite or aragonite. Mineral springs that produce travertine can be hot, warm or even cold.If the roof of a cave collapses, a sinkhole could form. Some sinkholes are large enough to swallow up a home or several homes in a neighborhood.