Uncovering a Geological Mystery
Huge salt deposits indicate that the Mediterranean once dried up. Evaporated.
The salt deposits are up to 3 kilometers (almost 1.9 miles) thick, and water levels dropped by several hundred meters.
It’s one of the greatest vanishing acts in earth history.
Today, water flows from the Atlantic Ocean into the Mediterranean Sea through a narrow passageway known as the Strait of Gibraltar. That is the main source of water. Rivers contribute some water, but most of it comes from the Atlantic Ocean.
But somehow, at some point, that main source of water got shut off.
That led to the “Messinian Salinity Crisis.” The MSC. But what triggered that crisis?
Some scientists believe it was caused by an ice age. During an ice age, the water that normally goes into the Atlantic Ocean gets locked up on land as ice, which deprives the Mediterranean Sea of its main water sources; the Atlantic Ocean and the rivers that normally feed into the Mediterranean Sea.
But other scientists found that some of the salt was deposited during a time when both sea levels and global climate had remained comparatively stable.
The second idea was that maybe tectonic events had somehow blocked off the narrow passageway.
Other scientists thought it might have been a combination of shifting crust and climate change, that the crust under the Strait of Gibraltar had lifted up over time.
Then, as temperatures rose and fell, thereby changing the amount of water pouring into the Mediterranean Sea from the river the fed it, the amounts of salinity fluctuated.
At first, I agreed with the first theory, that ice ages were the only cause, because the Mediterranean Sea has dried up many times, and those periods of evaporation coincided with Milankovitch cycles (see graph at 5:33 in).
However, newer studies show that the Mediterranean Sea filled up again in as little as two years, which to me indicates that there may indeed have been a tectonic event.
However, that explanation would work for me if such a tectonic event had happened only once.
But that’s not the case. In-as-much as the Mediterranean Sea has dried up many times – in sync with Milankovitch cycles – wouldn’t this mean that the same sort of tectonic event had to have lifted the crust, in the same way, at the same location, many, many times? I’m having a tough time buying into that explanation.
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January 7, 2021 at 12:24PM