Catastrophic flood of the Mediterranean after the Messinian salinity crisis

Taken at the flood Around 5.6 million years ago the Mediterranean Sea became disconnected from the world's oceans and during the period that followed, known as the Messinian salinity crisis, sea levels fell dramatically as the waters evaporated. The water returned, about 5.3 million years ago, but the details about this, the largest known flood in Earth's history, remain sketchy. A study making use of boreholes, seismic data and numerical modelling suggests that it was a catastrophic event: though it started as a trickle that may have lasted several thousand years, as much as 90% of the incoming water was transferred in less than two years. Such an abrupt flood may have involved peak rates of sea level rise of more than 10 metres a day. 5.33 million years ago, in an event known as the Zanclean flood, Atlantic waters refilled a mostly desiccated Mediterranean Sea which had become disconnected from the world's oceans; however, the nature, abruptness and evolution of this flood remain poorly constrained. Using borehole and seismic data and a model study, it is now suggested that 90 per cent of the water was transferred in a short period of a few months to two years, with peak rates of sea level rise in the Mediterranean possibly reaching more than 10 metres per day. The Mediterranean Sea became disconnected from the world’s oceans and mostly desiccated by evaporation about 5.6 million years ago during the Messinian salinity crisis 1 , 2 , 3 . The Atlantic waters found a way through the present Gibraltar Strait and rapidly refilled the Mediterranean 5.33 million years ago in an event known as the Zanclean flood 4 . The nature, abruptness and evolution of this flood remain poorly constrained 4 , 5 , 6 . Borehole and seismic data show incisions over 250 m deep on both sides of the Gibraltar Strait that have previously been attributed to fluvial erosion during the desiccation 4 , 7 . Here we show the continuity of this 200-km-long channel across the strait and explain its morphology as the result of erosion by the flooding waters, adopting an incision model validated in mountain rivers. This model in turn allows us to estimate the duration of the flood. Although the available data are limited, our findings suggest that the feedback between water flow and incision in the early stages of flooding imply discharges of about 10 8 m 3 s -1 (three orders of magnitude larger than the present Amazon River) and incision rates above 0.4 m per day. Although the flood start