For decades, it’s been “snowing” salt in the deepest parts of the Dead Sea, a phenomenon that has stumped researchers studying one of the world’s saltiest bodies of water. Researchers with the American Geophysics Union now believe they know how this process takes place, lending a deeper understanding to how salt builds up in the Earth’s crust.
Since the 1970s, freshwater diversion from waterways feeding into the Dead Sea – a salt lake bordering Jordan and Israel – has lowered the water level of the Dead Sea, which in turns makes the water saltier. For years, researchers have observed salt layers that form along the top layer of the water that snow down to pile up along the lakebed at a rate of about 10 centimeters (4 inches) every year in upright finger-like structures. It defies physics, or at least geologists thought it did.
“The initial fingers might only be a few millimeters or a couple of centimeters thick, but they’re everywhere across the entire surface of the lake,” said study co-author Eckart Meiburg said in a statement.
During the summer months, heat warms the surface of the lake and divides it into two layers: a warm top layer and a colder, less salty layer of water below. The top layer becomes saltier as the heat evaporates water from it. A previously proposed theory suggested that as the top layer is disturbed by waves and other motions, tiny parcels of warm water can move down into the colder, denser water. Heat diffuses quicker than salt and as the warm water cools salt precipitates out to form sinking crystals, or “snow” in a process the team calls fingering.
“Initially you form these tiny fingers that are too small to observe… but quickly they interact with each other as they move down, and form larger and larger structures,” said lead author and mechanical engineer Raphael Ouillon.
Until now that was just a theory. Publishing their work in Water Resources Research, researchers developed a computer simulation that shows how this process might occur. It confirms their salt “finger” theory. The Dead Sea is the only hypersaline body of water on Earth that researchers have recorded this process, making it a unique natural laboratory.
Underwater drone footage reveals the salt flakes falling like snow.
“Altogether this makes the Dead Sea a unique system,” said geologist and study co-author Nadav Lensky. “Basically, we have here a new finding that we think is very relevant to the understanding of the arrangement of these basins that were so common in Earth’s history.”
The findings help researchers understand the physics of the Dead Sea, as well as how salt deposits found within the Earth’s crust may develop and build, such as the thick salt layer formed beneath the Mediterranean Sea.