The formation of the Mediterranean Sea is a tale of dramatic geological transformation. It began with the collision of the African and Eurasian continental plates around 70–60 million years ago, which closed off the Tethys Sea, an oceanic basin that lay between these continents. This collision caused the subduction of the Tethys oceanic plate and led to significant volcanic activity and a mountain-building zone across northern Africa and southern Europe.
Approximately 6 million years ago, this collision isolated the remains of the Tethys Sea from the Atlantic Ocean, starting a period of extensive drying. The evaporation of the trapped seawater resulted in the deposition of thick salt layers, some exceeding 1.9 miles (3 kilometers) in thickness. This “salinity crisis” nearly desiccated the former Mediterranean Sea over more than 600,000 years.
The crisis ended abruptly around 5.3 million years ago when a natural barrier between the Atlantic Ocean and the Mediterranean basin broke at what is now the Strait of Gibraltar. This breach allowed ocean waters to rush back into the basin at an astounding rate, refilling parts of it by up to 30 feet (10 meters) per day, leading to the formation of the modern Mediterranean Sea within a few months.
Fossil evidence indicates that the climate of this region, once humid and subtropical, began transitioning to the drier Mediterranean conditions we know today a few million years ago. The landscape evolved to be dominated by coniferous trees and other flora adapted to hot, dry summers. Over thousands of years, human activities have further significantly altered the ecology of the Mediterranean region, showcasing the interplay between natural processes and human influence in shaping our planet’s environment.
