The Mediterranean is the remnant of the geologically ancient Tethys Sea being closed by the northward movement of the African Plate against the Eurasian Plate. The line of subduction of Africa under Eurasia runs in a general E-W direction through the Mediterranean. The southern margin of Eurasia rises over the subduction to become the mountains of the Alpide Zone as though they were folded up by compression, and to some extent they are. The subducted plate exerts a pressure on the overriding plate normal to the plane of contact. This force vector at any point of the boundary has a vertical component, pushing up the margin, and a horizontal component, compressing and folding the uplifted land.
