Geology of Belize Caves
The Yucatan peninsula is a huge limestone block. Where this block borders the Maya Mountains, uplifting and folding has occurred, exposing multiple cave systems. A cave in southern Belize contains the second largest underground room in the world, over 1 km. long and hundreds of feet high, and when discovered in the 1980’s it was the largest room yet found. A cave in Indonesia currently holds the world record.
Limestone is a rock composed of remains of marine life (shells), and the precipitates of calcium carbonate that collect on the floor of tropical seas. Coral is also a big contributor to limestone formation. When limestone is uplifted or shifted due to geologic processes, it often becomes part of a continent and thus is exposed to groundwater movement. This water then is able to dissolve the limestone beds into cave formations.
Water dissolves limestone by slowly chemically bonding with calcium carbonate, which is then carried away in suspension with the groundwater. Regular erosion due to the surface water movement (rivers and rain) also occurs. Rainwater percolating down through limestone encounters organic debris on the surface, and picks up CO2 as part of the process, forming week carbonic acid, which also slowly dissolves calcium carbonate. When the acidic rainwater meets the calcium carbonate laden groundwater, a chemical imbalance occurs which causes the water to rapidly dissolve more limestone, up to 25 times more than it could otherwise. This reaction is what causes such extensive “solution erosion” to occur, which forms the huge underground caverns found in cave systems. This process is most active in tropical, rainy regions like Belize.
Just the opposite action occurs when a cave is uplifted (or groundwater drops) and exposed to air. When percolating acidic groundwater that has already dissolved some limestone hits the air, another chemical imbalance occurs and limestone is then rapidly deposited (precipitated out of solution) in the cave as “dripstone” formations. These are the stalactites, columns, curtains, and other “flow stone” formations found in caves.