Over millions of years the oceans reef systems created layers upon layers of limestone. Some of these layers were small, only a few feet thick, while others were hundreds of feet thick.

Many of these layers where softer and more porous than others, making them more susceptible to the effects of moving water.

During the millions of years the land was above sea level, rainwater filtered down through the limestone layers and formed underground rivers within the softer rock layers.  Over millions of years these underground rivers grew larger creating extensive subterranean cave passages.

The softer limestone layers dissolved quicker, many times creating massive underground water filled chambers several hundreds of feet long, wide, and deep.

During the periods of extreme low ocean levels, such as the last ice age, sections of the cave contained dry air chambers.

At one point in time, the rock ceiling over this large subterranean chamber could no longer hold up the immense weight and collapsed into the chasm below, creating a natural sinkhole.    

Years of surface debris such as trees, soil, leaves, and dead animals start to fill up the sink.  If the debris rises high enough within the sink, it can cut off the ancient cave system restricting or closing off the water flow. The Myakka Deep Hole, is a dead sink.

A dead sink refers to a closed water flow system. No water movement occurs from the aquifer creating a stagnant pool of low oxygenated water. Many times these types of systems can turn into important archeological sites due to the anaerobic environment helping to preserve animal and plant remains that have fallen into the sink.