The process of karst formation involves what is referred to as "the carbon dioxide (CO₂) cascade." As rain falls through the atmosphere, it picks up CO₂ which dissolves in the droplets. Once the rain hits the ground, it percolates through the soil and picks up more CO₂ to form a weak solution of carbonic acid: H₂O + CO₂ = H₂CO₃. The infiltrating water naturally exploits any cracks or crevices in the rock. Over long periods, with a continuous supply of CO₂-enriched water, carbonate bedrock begins to dissolve. Openings in the bedrock increase in size and an underground drainage system begins to develop, allowing more water to pass, further accelerating the formation of karst. Eventually this process leads to the development of subsurface caves. (Illustration by M. Nyhof.)