The Messinian salinity crisis.
Millions of years ago, a dramatic and nearly catastrophic transformation reshaped the Mediterranean Sea. Known as the Messinian Salinity Crisis (MSC), this event occurred approximately 5.5 million years ago, when nearly three-quarters of the Mediterranean’s water vanished into the atmosphere. Now, groundbreaking research sheds new light on the series of events that led to this geological phenomenon, providing fresh perspectives on a long-debated mystery.
Two Phases of the Messinian Salinity Crisis
According to the new study, the MSC unfolded in two distinct phases, both driven by restricted water flow between the Atlantic Ocean and the Mediterranean. Scientists used advanced techniques, including the analysis of chlorine isotopes in ancient seabed salt and sophisticated numerical modeling, to trace the timeline and mechanics of this massive event.
Phase One: For 35,000 years, water flow between the Atlantic and the Mediterranean was severely restricted through what is now the Strait of Gibraltar. With no consistent influx of freshwater, evaporation rates skyrocketed, leaving behind thick layers of salt and drastically lowering water levels.
Phase Two: Over the next 10,000 years, the Mediterranean became completely isolated. This intensified evaporation and resulted in the formation of dramatic geological features. In some areas, water levels plummeted by as much as 2.1 kilometers (1.3 miles), creating vast, desolate basins.
As water retreated during phase two, the Strait of Sicily’s underwater ridge emerged as a land bridge, effectively dividing the Mediterranean into two separate basins. This division accelerated evaporation in the eastern basin, where the most significant salt deposits have been discovered.
A Complex Debate, A Unified Answer
For years, scientists have debated whether the MSC was caused by full isolation from the Atlantic or by limited water flow. This study bridges the gap between these theories, showing that the crisis was indeed a two-phase process involving both partial and complete isolation.
While the exact reasons for the Mediterranean’s isolation remain unclear, the late Miocene period saw widespread tectonic upheaval. These shifts likely played a critical role in triggering the crisis. Additionally, the MSC itself caused enormous geological stress, altering crustal dynamics and drying out surrounding landscapes.
The study authors emphasize that the sheer magnitude of the Mediterranean’s water loss would have had global repercussions. “The huge size of the Mediterranean depression created by MSC water level drawdown – corresponding to a volume loss of 69 percent of the Mediterranean water body – would have generated planetary-scale climate effects, inducing changes in precipitation patterns,” the researchers explain.
Modern Implications of an Ancient Crisis
Today, the Mediterranean’s connection to the Atlantic through the Strait of Gibraltar prevents such a crisis from recurring. However, if this natural connection were severed, the sea level would drop by an estimated half a meter (20 inches) annually.
The MSC ultimately came to an end with the Zanclean flood, when Atlantic waters poured back into the Mediterranean, refilling the basin. This pivotal event not only reversed the effects of the crisis but also reshaped the region’s geography and ecosystems.
The new findings underscore the far-reaching implications of the MSC, offering insights into geological, biological, and climatic changes that reverberated far beyond the Mediterranean. As the researchers conclude, “Our results have broader implications for the biological, geologic, and climatic evolution of the Mediterranean realm, and beyond.”
The featured image shows the Kornati Islands national park in my home country Croatia.