Why is the Dead Sea so salty?

The Dead Sea is one of Earth’s saltiest bodies of water. But how did it get that way?

It lies in a deep rift valley that was periodically flooded by the Mediterranean Sea in ages past. About two million years ago, the surrounding land rose high enough to block the floods, and seawater became trapped in the valley. Much of the floodwater evaporated as the climate became arid, leaving behind a small, salty lake known as the Dead Sea.

The Dead Sea’s water levels have fluctuated over the millennia, but levels have plunged in recent decades, making it even saltier than before. It’s so salty now that when scientists lower cables into the water to take measurements, the cables get coated in thick, hard salt crystals.

Curiously, Israeli geologists have noticed salt crystals “snowing” through the Dead Sea’s water and piling up on the deepest parts of the lakebed since 1979. The process driving this salt crystal “snow” has puzzled scientists ever since, but a new study may have solved the decades-old mystery.

The study authors propose that tiny disturbances in the lake, caused by waves or other motion, create “salt fingers” that slowly funnel salt down to the lakebed. The animation in this video shows how the salt fingers form and transport salt downward.

The new finding helps researchers better understand the physics of the Dead Sea and what might happen as the lake continues to evaporate. It also helps explain the formation of massive salt deposits found within Earth’s crust, like those beneath the Mediterranean Sea.