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Natural Bridge Caverns in the Edwards Aquifer recharge zone offer a captivating underground world shaped by water flow and calcite formations. Learn about the cave's unique features and ongoing scientific studies, and discover how to protect this delicate ecosystem. Follow guidelines to preserve the cave's beauty for future generations.
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Natural Bridge Caverns lies within the recharge zone of the Edwards Aquifer. Figure from Musgrove (2000) after Burchett et al. (1986) and Brown et al. (1992); precipitation contours from Larkin and Bomar (1983).
This is the map view of Natural Bridge Caverns. Map from Elliott and Veni (1994) The cave transports water to recharge the Edwards Aquifer.
Water can enter the cave through fractures (fracture flow) or by seeping through the permeable rock itself (diffuse flow). Diffuse Flow Fracture Flow
As the slightly acidic rain water passes through rock, it dissolves away calcite and enlarges cave passages.
Stalactite Cave formations such as stalactites, stalagmites, columns, and flowstone develop when the calcite is redeposited. Column Stalagmite Flowstone
The North Cavern has several spectacularly clear pools of water. Calcite deposits around the rims of the pools indicate past water levels.
Map from Elliott and Veni (1994) Purgatory Creek is a perfect location to observe changes in the water level of the aquifer. After heavy rains, the water table can rise to flood this entire room, submerging the walkway.
Science in Natural Bridge Caverns University of Texas scientists have set up experiments to study the relationships between water chemistry, drip rates, and how fast formations grow.
Samples from glass plates like this one at Castle Tabletop give an exact measurement calcite deposition of over time. Water samples collected from the drips above the formation are analyzed for chemical composition.
How you can help protect the cave? • Remember, the Natural Bridge Caverns are LIVING caves.Touching formations or getting off trail will cause irreparable damage. • Keep the caves as clean as possible.Do not bring food, candy, gum, drinks, water bottles, backpacks, or strollers into the cave. • Stay with the group and listen to the guide.Several tours are in the cave at the same time.