The swiss-cheese terrain of caves, sinkholes, and subterranean streams develops where highly soluble carbonate rocks, limestone and dolomite, lie close to land surface. Where the rocks are full of fractures and precipitation is a generous 36 to 48 inches per year, water continually flows through the cracks and between layers (called bedding planes), and "eats" them away.
Limestone is made up of the mineral calcite, a combination of calcium, carbon, and oxygen. Magnesium added to the formula produces the mineral dolomite, which largely makes up the sedimentary rock called dolomite.
Rainwater picks up carbon dioxide, first as it passes through the atmosphere, then as it contacts air in the soil. The water reacts with carbon dioxide to form a mildly acidic water that gradually dissolves carbonate rocks. The result is a karst landscape.