What do you think of this fact?
A lake at the bottom of the sea sounds like a contradiction. Water inside water? But in the Gulf of Mexico, that’s exactly what you find.
Too salty for the sea
According to NOAA’s Ocean Explorer, these brine lakes form when seawater dissolves buried salt deposits. That salt is a leftover from a time when the Gulf dried out, and in places the layer of salt and minerals is up to 8 kilometers thick. The result is brine that is many times saltier than seawater. Because it is denser than the water around it, it collects in dips on the seafloor instead of mixing in.
That’s why these pools have something you’d never expect underwater: a distinct surface and a shoreline. NOAA describes brine lakes from as small as 1 meter across to as long as 20 kilometers. Their shores are often lined with dense beds of mussels that live off the methane dissolved in the brine.
The Jacuzzi of Despair
The most famous example has a nickname straight out of a horror film: the “Jacuzzi of Despair”. A team including Temple University biologist Erik Cordes studied it with remotely operated vehicles. It lies more than 1,000 meters below the surface, and its water is four to five times saltier than the surrounding ocean.
According to WFTV, the pool is about 30 meters wide and almost 4 meters deep. Its brine is about 18 degrees Celsius, while the water around it is about 4 degrees. The Christian Science Monitor reports that the brine even spills over one side of the crater in a waterfall. Most larger animals stay away. According to WFTV, crabs that end up in the brine die and, as one scientist put it, “get pickled and preserved”. Cordes summed up the view like this: “It feels like you are not on this world.”
Bonus fact: The salt behind these lakes is ancient. NOAA dates the thick salt layer to the middle Jurassic period, when the Gulf of Mexico was a shallow sea.
So the deep sea doesn’t just contain water. It contains lakes with shorelines, and at least one of them has a waterfall.