The Hellenic Arc is a great subduction zone curving through the eastern Mediterranean south of Crete and the Greek islands, from the Peloponnese to Rhodes. Along it the African Plate slides beneath the Aegean microplate, making it the most seismically and volcanically active subduction system in Europe.
As the African slab descends into the mantle, it generates both shallow thrust earthquakes near the trench and deeper events, as well as feeding the volcanoes of the Aegean arc, including Santorini. The arc is also capable of producing tsunamis when large offshore ruptures displace the sea floor.
The zone unleashed the catastrophic 365 AD Crete earthquake, estimated above magnitude 8, which lifted parts of western Crete several metres and sent a devastating tsunami across the eastern Mediterranean to Alexandria. Modern events such as the 2020 Samos–İzmir earthquake (magnitude 7.0) confirm the arc's continued destructive potential.