The Flower Garden corals grow on top of geological structures called salt domes, or salt diapers. Millions of years ago, when the Gulf of Mexico was very shallow, evaporation caused the deposit of thick layers of salt onto the sea floor. Over time, runoff from the rivers of the North American continent covered the salt with huge amounts of silt and mud. The salt, being much less dense than this mud layer, was forced upwards by the pressure of the weight on top of it. In weak spots, the salt was able to push its way through the mud layers, and in some areas, make its way to the surface - causing an area of high salinity as the salt is dissolved into surrounding waters. One such area is located at the East Bank of the Flower Gardens - at around 240' - the brine seep. An area of the bank, called the graben, is a depressed area about a mile across, caused by the loss of salt from the salt dome. Associated with this brine seep is an underwater brine waterfall, brine lake, and brine river. As you can see in this image, the brine river is visibly different from the surrounding water. (photo: Dr. Tom Bright)