About 5.5 million from years ago a critical and almost catastrophic transformation has reshaped the Mediterranean Sea: this geological event, which lasted almost 700,000 years and known as “Messinian salinity crisis” (from the name of the geological period in which it occurred) and resulted evaporation of almost all the water in the Mediterraneantransforming it into a vast expanse of salt marshes and deserts. The causes of this extraordinary event are linked to complex climatic and geological changes, including the rising of the Alps and the closure of the Strait of Gibraltarwhich interrupted the flow of water from the Atlantic Ocean. The consequences of this event not only affected the Mediterranean basin, but had a significant impact on the surrounding ecosystems and changed the planet’s climate. A recent study conducted by a team of researchers and published in the journal Nature has shed new light on the events that led to this geological phenomenon, providing new perspectives on a “mystery” long debated in the scientific community.
The two phases that led to the salinity crisis in the Mediterranean
Through a detailed analysis of marine sediments and geological evidence, including the analysis of chlorine isotopes in the ancient salt of the seabed and sophisticated numerical models to trace the chronology and mechanism of the event, researchers have identified two phases very distinct. In the first phaseduration approx 35,000 yearsthere was a progressive reduction in the supply of water from the Atlantic Ocean to the Mediterranean, due to tectonic movements which began to narrow the Strait of Gibraltar. This change caused an increase in salinity in the waters of the basin, altering marine ecosystems and triggering the first deposits of evaporite minerals.
In the second phasewhich occurred in less than 10,000 yearsthe Mediterranean was almost completely isolated from the Atlantic Oceanwith a consequent almost total drying up of its waters. The sediments of this last phase testify to the accumulation of enormous quantities of salts, which today form thick layers of plaster And halite on the bottom of the basin.
As the water gradually retreated during the second phase, the underwater crest of the Strait of Sicily emerged, dividing the Mediterranean into two distinct basins, thus forming a land bridge between Africa and Europe. This split accelerated evaporation in the eastern basin, where the most significant salt deposits were discovered. The researchers, led by Giovanni Aloisi of the French National Center for Scientific Research (CNRS), found that in some areas, the water level would have dropped to 2.1 km.
Because the Mediterranean Sea dried up almost completely
After years of debate and research, the scientific community has reached a consensus on the two main phases that characterized the Mediterranean Salinity Crisis. Although researchers have not yet precisely pinpointed the main reason of the isolation of the Mediterranean during the Salinity Crisis, it is clear that the late Miocene it was a period of intense tectonic activitywhich played a crucial role in determining the evolution of the basin. Between 5.96 And 5.33 million from years agothe movements of the tectonic plates radically modified the geography of the region, creating the conditions for the progressive isolation of the Mediterranean from the Atlantic Ocean.
This research is of fundamental importance both for understanding the geological history of our planet and for addressing the climate challenges and environmental issues of the present. This extraordinary event, which saw the almost complete drying up of the Mediterranean and the formation of vast salt deposits, represents a unique case, and in this regard the researchers conclude by stating: “Our findings have broader implications for the biological, geological, and climatic evolution of the Mediterranean realm and beyond“.
