Rising crust left the Mediterranean dry

Water supply blocked over the Strait of Gibraltar five million years ago

Mediterranean © NASA / GSFC
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About five million years ago, the Mediterranean was cut off from the Atlantic and dried up completely. Why this happened, explains now a Dutch geologist in the journal "Geology". He provides data that prove that an upward movement of the earth's crust locked the strait of Gibraltar like a dam and thus prevented the supply of water.

Principle "Mattress"

As the sea level drops, so does the pressure of the ocean on the underlying earth's crust. In response, she "springs up" like a mattress when the sleeper rises. According to Rob Govers, geologist at Utrecht University, this process could be responsible for the complete drying up of the Mediterranean five million years ago.

Heavy evaporation and insufficient inflow through rivers initially lowered the sea level in the Mediterranean. At the same time, the earth's crust began to rise until the strait of Gibraltar was completely above sea level, preventing water from flowing from the Atlantic into the Mediterranean. Deprived of this supply, the sea level continued to drop until the sea eventually fell completely dry.

African plate sinks dam again

However, according to geological standards, this condition did not last very long: 170, 000 years later, the "dam" was once again history and seawater was once again able to flow into the now dry, gigantic Mediterranean valley. According to Govers, the earth's crust also played a decisive role in this process. As a result of the north migration of the African plate, it slid under the Eurasian and pulled it down through its weight.

As a result, the entire region sank slightly and the strait of Gibraltar disappeared again below sea level. The fact that the subduction at this point actually leads to a mass increase in depth, shows Gover by gravity measurements and scans of the crust: Even today, the data to a large mass in about 400 kilometers depth. display

(Utrecht University, 12.02.2009 - NPO)