The Mediterranean Sea was once dried out, leaving behind a mile-high layer of salt all across the sea floor.
This ancient phenomenon is know as the Messinian Salinity Crisis.
Here is an explanation by University of Maryland professor Daniel Kirk-Davidoff:
“In 1970, an undersea drilling project began taking samples of the Mediterranean’s ocean floor. They discovered an area of salt up to 3 kilometers thick and located 100-200 meters below the ocean floor, which they named the M-reflector. By studying the salt, they found that the Mediterranean Sea must have dried up at one point millions of years ago for an extensive period of time.
They called this drying of the Sea the Mediterranean Salinity Crisis (MSC). The MSC began approximately 6 million years ago (MYA) and lasted until around 5.3 MYA – a time span of well over a half million years! Although scientists are still not completely sure about the cause of the MSC, they do have evidence that offers some explanations.”
From Nature magazine, 10 April 2003:
“The Messinian salinity crisis–the desiccation of the Mediterranean Sea between 5.96 and 5.33 million years (Myr) ago–was one of the most dramatic events on Earth during the Cenozoic era. It resulted from the closure of marine gateways between the Atlantic Ocean and the Mediterranean Sea, the causes of which remain enigmatic.”
Here is an excerpt from a 2013 Live Science story about the phenomenon.
“Though scientists understood some of what triggered the great salinity crisis, they still don’t fully understand the climatic changes that may have been involved. The Earth wobbles like a top around its axis as it spins, in a roughly 20,000-year cycle. That shift affects how much sunlight certain parts of the Earth receive at different points in the cycle, thereby changing the climate. In the Mediterranean Sea area, sediments are striped with dark and light bands that correspond to surges and die-offs of sea life as a result of those climactic shifts.”
As researchers discovered, the Mediterranean Sea still received water from Africa during this period.
“Ancient rivers in North Africa dumped huge pulses of freshwater into the sea in late summer, leaving traces of surging biological activity in the fossil record, the models show. Based on their simulations, the researchers found the freshwater pulses happened at a time in the Earth’s orbital rotation when the Northern Hemisphere would experience colder winters and hotter summers. That, in turn, meant that the evaporation must have started much later in the Earth’s orbital cycle.”
The aforementioned wobbling of the Earth is a part of the Milankovitch Cycles.
From the OSS Foundation: “What are Milankovitch Cycles? Natural global warming, and cooling, is considered to be initiated by Milankovitch cycles. These orbital and axial variations influence the initiation of climate change in long-term natural cycles of ‘ice ages’ and ‘warm periods’ known as ‘glacial’ and ‘interglacial’ periods.”
As for those long-term natural cycles . . .
“The earth has only had its current atmosphere for about 400 million years. In that time, Earth has had climates ranging from being almost completely covered in ice to times when even the poles were subtropical.” – North Carolina Climate Office
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