Why is the Black Sea basin considered a structural downwarp in Earth’s crust?

The Black Sea basin is characterized as a vast structural downwarp—a significant and unusual depression in Earth’s crust—due to its unique internal composition and geological formation.1

The core of this deepwater depression features a distinct layering of the crust. It consists of a sedimentary layer and a basaltic layer, with a granite layer thrust between them at the periphery of the basin. This structural configuration distinguishes the basin from surrounding regions, which are influenced by the ancient Precambrian rocks of the Russian Platform and other sedimentary platforms.1

Geologically, the basin is believed to be a residual feature of the ancient Tethys Sea. Its current form emerged following structural upheavals in Anatolia during the Paleocene Epoch, which isolated the basin from the ocean. Over millions of years, the surrounding mountain ranges—including the Caucasus and Carpathians—rose, while the basin itself continued to be shaped by ongoing earth movements and sea level changes.1