When the water table lowers, the support system for the overlying rock is removed. Figure 16-27 in Chernicoff Hazards include contamination of water from waste entering a sinkhole. Cave Formation Formation takes thousands of years. Next, water table drops below original level, exposing open fractures to air. Underground streams now can erode weathered limestone, causing the fractures to get larger.
Streams continue to connect fractures, creating a network of passages.
Speleothems precipitation of CaCO 3 from solution. Stalagmites as water drips from the ceiling, it lands on the floor. Most of the water evaporates, precipitating CaCO 3 . Evaporites tend to dissolve completely. Limestone bedrock lies just beneath the surface of of North Central Iowa.