Γεωλογική δομή και εξέλιξη της Θηρασίας: η παλαιοτοπογραφία της νήσου πριν τη μινωική έκρηξη (Geological formation and evolution of Therasia: the palaeotopography of the island before the Minoan eruption)

Therasia island is one of the three segments of the Santorini volcanic cone which stood above sea-level after the last large catastrophic eruption of the Santorini volcano in the Late Bronze Age (1613± 14 years BC) (Friedrich et al. 2006), also known as the “Minoan” eruption. The oldest rocks outcropping above sea-level today at Therasia are 172.000 years old, while the youngest tephra layers covering the island are those deposited by the Minoan eruption. The present study describes geological formations which form the island, as they are reported in the new attached geological map in 1:10.000 scale, as well as the mechanism and the time period of their deposition. Based on the above information as well as on field observation and assumptions, the palaeotopography of the island before the Minoan eruption –which gave Santorini its present form– is accurately depicted. Pre-Minoan Therasia occupied a significantly smaller area than the present one, as the largest plain in today’s Therasia west sector consists of tephra deposited by the Minoan eruption. Because of this, any Late Bronze Age housing and traces of habitation that have been already found or are expected to be uncovered, are located in the stiff cliffs of the island or in the eastern border of the present-day west plain sector.