Extensive mining and agriculture in west central Florida have lowered the water table enough to turn springs into sinkholes along the Peace River, which each day loses about 11 million gallons, or 8 percent of its flow, to these underground caverns.

On June 27, 1994, a gaping sinkhole developed in a 400-acre, 220-foot-high gypsum stack containing a liquid impoundment of acid and ammonium. "About 4 million cubic feet of phosphogypsum and an undetermined amount of acidic water disappeared through that shaft into the ground," says Ann Tihansky, a scientist with the U.S. Geological Survey.

The waste liquid in this image is the result of processing raw phosphate with sulphuric acid; it can be both acidic and faintly radioactive due to uranium that is found with phosphate ore.