The floodgates of 5.33 Ma

I’ve had a paper sitting on my desktop for a couple of weeks: “Catastrophic flood of the Mediterranean after the Messinian salinity crisis”, by Garcia-Castellanos and colleagues. A little over 5 million years ago, the Mediterranean Sea was mostly dry, water broke through the Strait of Gibraltar, and filled it back up. A big flood, but nobody has really been sure how long it took – was it like the process of emptying post-glacial lakes, for instance?

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. 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 108?m3?s-1 (three orders of magnitude larger than the present Amazon River) and incision rates above 0.4?m per day. Although the flood started at low water discharges that may have lasted for up to several thousand years, our results suggest that 90 per cent of the water was transferred in a short period ranging from a few months to two years. This extremely abrupt flood may have involved peak rates of sea level rise in the Mediterranean of more than ten metres per day.

I just really like the idea of a giant sluice of seawater eroding a big canyon through the Strait.

References:

Garcia-Castellanos D, Estrada F, Jiménez-Munt I, Gorini C, Fernàndez M, Vergés J, De Vicente R. 2009. Catastrophic flood of the Mediterranean after the Messinian salinity crisis. Nature 462:778-781. doi:10.1038/nature08555