Strogili was a volcanic island, which was created during the period of the Quaternary, and which owed its name to its circular shape. The volcanic system that created it is the most active in Greece and one of the most violent in the world. In the last 400,000 years it has produced 12 catastrophic eruptions, which typically caused caldera sinking. Then new volcanic cones gradually emerge, a process that continues until the next catastrophic eruption. After the Minoan eruption, around 1613 BC, an elliptical caldera was created in the central part of the island, the axis of which is about 11 km from north to south and the axis from east to west 7.5 km, while remnants of the prehistoric of the island are today’s Santorini, Thirasia and Aspronisi.
A small passage between the place where the Lighthouse of Akrotiri and Aspronisi is today allowed the sea to enter a caldera, in the center of which was the top of an underwater volcano similar to today’s Kamenes. The cone of the Minoan eruption must have been located near present-day Fira, which is proven by the greater thickness in this area of the first layers of volcanic ivy.
Strogili was inhabited as early as 6,000 BC, as evidenced by finds found in a mine in Fira, while to date pre-eruption settlements or signs of settlements have been found in Thirasia, Akrotiri and Megalochori in Santorini. Especially in the prehistoric settlement of Akrotiri has been found a large number of murals that give us a pretty good picture of the landscape before the great volcanic disaster. A typical example is the mural of Spring. It is considered to have had one of the richest fauna and flora in the Aegean.