In the geological history of Mediterranean Sea hides one of the most surprising episodes related to the salinityMillions of years ago, the Mediterranean basin witnessed a phenomenon that defies current understanding: a process that transformed its waters into an immense salt marsh and, subsequently, into a freshwater lake with enormous level fluctuations. This event, known as the Messinian Salinity Crisis (MSC), is an object of fascination for the scientific community and, recently, an international team has provided new keys to understanding it.
What we see today as a blue, salty sea was, for a brief but intense period, isolated from the Atlantic Ocean. During this time, the The Mediterranean experienced extreme drops in level and large accumulations of salt., leaving behind traces that can still be read in the sediments of the seabed and in the geological formations of the areas closest to the Strait of Gibraltar.
Salinity crisis: from the Mare Nostrum to a gigantic salt mine
The phenomenon of CSM It dates back to a few years ago 5,6 million years, when tectonic movements closed the last channel between the Atlantic and the Mediterranean. The inflow of water stopped, while evaporation continued at a considerable rate. As a result, The sea level dropped dramatically, losing up to more than a kilometer in some areas, and the basin was filled with salt deposits in immense quantities.
During this period, rivers such as the Nile, the Ebro, the Po and the Rhône were unable to provide sufficient flow to compensate for the loss of water through evaporation.If a dam had been built in Gibraltar, as some have theoretically proposed, The level of the Mediterranean would have dropped between 0,75 and 1 meter per year, repeating the scenario of that historic crisis. The resulting image is that of a sea reduced to lagoons and salt flats at its bottom, a fact clearly evidenced by the sedimentary records.
This extraordinary situation also left a legacy in the form of contrasts in the geological recordSome witnesses suggest an almost complete emptying of the sea; others, the persistence of large volumes of water. Resolving this apparent contradiction has been one of the most exciting challenges for experts.
The role of Lake Mare and the connection with Paratethys
For more than 200.000 years of isolation, the Mediterranean depended only on the rain and rivers of Europe and Asia Minor. During wet periods, the water level rose; during dry periods, it fell. This pattern of fluctuations caused the sea to transform at times into a large lake, known as Lago Mare, whose level fluctuations still leave unanswered questions.
In this context, a fundamental role was played by Great Lake Paratethys, located north of the Mediterranean, whose surface today occupies the Central and Eastern European Plain. The Paratethys, through its connections with the Mediterranean, It provided fresh water in varying quantities and, when the differences in level between both lakes were very pronounced, the erosion of the straits intensified, widening the river channels and facilitating the flow of water towards the south.
When equilibrium was restored, the Mediterranean level rose, recovering part of what was lost, while the Paratethys level fell. The drier phases exacerbated the erosion process, creating river canyons and recording dramatic changes in the surrounding landscape and in the chemical composition of the waters.
Geological modeling: a new look at the past
A recent work, carried out under the coordination of Spanish and European researchers, has allowed to create a Numerical model that simulates the evolution of the Mediterranean during the CSMThis model integrates variables such as erosion, sedimentation, lithospheric movement, rainfall, and evaporation, achieving for the first time the reproduction of two geological scenarios that, until now, seemed incompatible: exposed seabeds and large volumes of water coexisting over time.
Thanks to this tool, experts can reconstruct the complex processes that determined the fate of the Mediterranean basin, Shedding light on how the sea recovered its current state after the reopening of the Atlantic connection 5,33 million years agoThe invasion of ocean waters ended the salinity crisis and marked a new era in the history of the Mare Nostrum.
Ecological consequences: a crisis in marine biodiversity
The impact of the extreme variability in salinity during the CSM was not only geological. The alterations in salt levels and temperature had devastating effects on marine ecosystemsAccording to several studies, the biodiversity declined drasticallyOnly a small percentage of the Mediterranean's endemic species survived this episode. According to records, the recovery of marine life and its original diversity took several million years.
In addition, these events created massive salt deposits which are now considered valuable natural resources and have been historically exploited in different parts of the world, such as Hallstatt in Austria or Khewra in Pakistan. lake sediments preserved in places like AlmerÃa and Málaga are still the subject of research and teaching practices for future geologists.
All this information, extracted from recent surveys and oceanographic campaigns, helps to understand the past of the Mediterranean and offers a framework for analyzing other systems affected by the isolation and salt accumulation on a global scale. The results contribute to a better understanding of ocean dynamics and their implications for ecosystems and climate.
