The Aegean Sea contains more than 1,000 islands and is the source of most of the Mediterranean’s cold, saline deep water. Before 1990 this source was in the Adriatic, but climate changes have led to increased winter cooling in the Aegean. It is a geologically complex area, as the Aegean microplate and the Anatolian Plate to the east are caught between the converging African and Eurasian plates. The Aegean crust is of continental thickness, but has been stretched and thinned, notably in the area of the Cretan Trough, so that much of it is now below sea level. The Hellenic Trough and Pliny Trench mark where the African Plate is subducting beneath the Aegean microplate. The Aegean Volcanic Arc stretches from Greece to Turkey through the southern Cyclades. These volcanoes are dormant or extinct, but earthquakes still occur at a depth of 95–105 miles (150–170 km). The islands of Santorini, in the southern Cyclades, are the remains of an explosive volcanic eruption around 1640 BC.
This was the largest volcanic event of the last 10,000 years and may have caused the downfall of Crete’s Minoan civilization. Behind the volcanic arc, the main Cyclades sit on top of a subsided plateau. At the northern end of the Aegean, a transform fault marks the contact with the Eurasian Plate, an area prone to strong, shallow earthquakes.