The Geology and Geomorphology of İstanbul

Abstract

The city of İstanbul is one of the most ancient sites of human dwelling in the world that has been continuously inhabited until today. It may indeed be the oldest. It enjoys a temperate climate characterised by wet winters and dry summers, although summer showers are not necessarily absent. Its geomorphology has been shaped by the movements of the level of the sea around it and the surface waters sculpting its multifarious rock types creating dominantly fluvial and karstic forms with a rich assortment of drowned coastal features. The Strait of İstanbul, the Bosphorus thracicus of antiquity, formed as a result of the marine invasion during the Flandrian transgression. The sea invaded through a structurally low-positioned watershed located between the oppositely tilted peninsulas of Thrace and Kocaeli (Bithynia). The seawater may have invaded the watershed of the Bosphorus some 8000 years ago, although whether the sea overtopped the Bosphorian watershed 8500 years ago or 7150 years ago is immaterial for the success of the model here proposed. The tilting of the two peninsulas created a fracture network that has controlled ever since the pattern of the fluvial drainage.