The eastern and western parts of the Mediterranean are separated by Sicily and the submerged Malta and Tunisian plateaus. The eastward flow from the western Mediterranean continues along the African coast, and a counter-clockwise circulation prevails in the eastern Mediterranean, and in the Ionian, Aegean, and Adriatic seas. Surface water becomes more saline through evaporation as it travels east, and starts to sink after cooling by winter winds. It then returns westward, exiting through the Strait of Gibraltar about 150 years after entering. The sea floor is dominated by the Mediterranean Ridge, a result of compression between the convergent African and Eurasian plates. These sediments are older—70 million years compared with 25 million years in the western Mediterranean. The Adriatic Sea is a shallow branch of the eastern Mediterranean. Rising sea levels at the end of the last ice age flooded valleys parallel to its eastern shore, giving rise to the islands of the Dalmatian coastline.