Caves most often form in areas of limestone, but on the coast they also occur in other rocks. Limestone is composed of calcite, which dissolves in the carbonic acid which can be found in rainwater and natural humic acids from decaying vegetation. Acidic water flowing through cracks and joints between the limestone and rock layers, breaking the surface in blocks of rock separated by deep cracks and potholes called also marked by sinkholes where surface currents can disappear. Underground, the acidic water dissolves the rock around cracks, opening a network of passages and caves, which can become large if the roof of the cave colapses. Several other features are formed when dissolved calcite is redeposited.
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