The cold seeps are formed by a process known as salt tectonics. During the Jurassic, the Gulf of Mexico was a shallow sea. It was cut off from the rest of the ocean, and eventually the water evaporated, forming huge salt deposits. Rifting caused the ocean connection to reopen and flood the area with sediment and water. The salt deposits were buried and preserved. As the sediment layer grew, it became heavier and heavier, causing the salt below to deform and move. Some of the salt deposits rose near the surface as domes. Other areas of salt seeped out, dissolved, and the denser water sank into lower basins.
The high salinity, high methane environment of the brine lakes creates a hostile environment for most ocean creatures. However, bacteria thrive in these locations. Often, the “shores” of the lakes are covered with methane-using (methantropic) mussels and clams. Giant tube worms with lengths up to three meters have been found in many cold seeps on the Gulf.
Photo of brine lake, East Flower Garden Bank, Gulf of Mexico, credit NOAA