A team led by Giovanni Aloisi, CNRS researcher and geochemist at IPGP, highlights the significant drop in the Mediterranean Sea level during the Messinian Salinity Crisis, a major geological event that transformed the Mediterranean into a gigantic salt basin between 5.97 and 5.33 million years ago.
The way in which one million cubic kilometers (around 240,000 cubic miles) of salt accumulated on the Mediterranean seabed over a short period of time remained unknown until now. Using an analysis of chlorine isotopes contained in salts extracted from the Mediterranean seabed, scientists retraced the two phases of this extreme desiccation.
In the first phase, lasting about 35,000 years, salts were deposited in the eastern part of the Mediterranean due to a partial restriction of its outflow to the Atlantic.
In a shorter second phase (less than 10,000 years), salts accumulated throughout the Mediterranean, causing a rapid drying out of the sea, with the water level dropping by 1.7 to 2.1 kilometers (5,577 to 6,889 feet) in the eastern Mediterranean and about 850 meters (2,789 feet) in its western part. As a result, the Mediterranean basin lost up to 70% of its water volume.
Artistic representation of the breaking of the Gibraltar threshold at the end of the Messinian Salinity Crisis. In the final moments of this crisis, the Mediterranean Sea level was about one kilometer (3,281 feet) lower than that of the Atlantic Ocean.
© Pibernat & Garcia-Castellanos
This dramatic drop in sea level likely had consequences for terrestrial fauna and the Mediterranean landscape. It may also have triggered volcanic eruptions in the region due to the lightening of the Earth's crust and created global climate effects linked to the depression thus formed.
These findings, published in the journal
Nature Communications, provide a better understanding of past extreme geological phenomena, the evolution of the Mediterranean region, and its worldwide repercussions.
The two phases of salt layer accumulation in the Mediterranean during the Messinian Salinity Crisis. During the first phase, salt accumulated in a brine-filled Mediterranean basin; in the second phase, salt accumulated in a completely isolated Mediterranean Sea from the Atlantic Ocean due to the significant drop in sea level in the western and eastern Mediterranean sub-basins.
© Giovanni Aloisi - This exceptional event covered the depths of the Mediterranean with a layer of salt up to three kilometers (1.86 miles) thick. Understanding the causes, consequences, and environmental changes experienced by the Mediterranean region in response to the Messinian Salinity Crisis has been a challenge engaging the scientific community for decades.
- The analysis of the two stable isotopes of chlorine (³⁷Cl and ³⁵Cl) allows scientists to estimate the rate of salt accumulation and identify any sea level drops.
Reference:
Nature Communications (2024).
DOI: 10.1038/s41467-024-53781-6
G. Aloisi, J. Moneron, L. Guibourdenche, A. Camerlenghi, I. Gavrieli, G. Bardoux, P. Agrinier, R. Ebner et Z. Gvirtzman, Chlorine isotopes constrain a major drawdown of the Mediterranean Sea during the Messinian Salinity Crisis.