The eastern Mediterranean Sea contains a surprisingly ancient chunk of oceanic crust, which is probably helping to shape the region's geology today.

The shifting of Earth's crustal plates has destroyed most oceanic rock older than about 200 million years. Roi Granot at Ben-Gurion University of the Negev in Beer-Sheva, Israel, investigated hints that the Herodotus Basin in the eastern Mediterranean might be older than that. Data from ship-towed instruments revealed long stripes of alternating magnetism on the Herodotus sea floor — a characteristic suggesting that it is oceanic, rather than continental, crust. The geometry of the stripes indicates that the crust dates back some 340 million years.

Earthquakes are a frequent occurrence on the sea floor where this relatively strong ancient crust meets weaker continental crust to the east.

Nature Geosci. (2016)