Geologically, Europe is not a separate continent but a subcontinent or a large peninsula of the Eurasian landmass. The conventional seven-continent model lists Asia, Africa, North America, South America, Antarctica, Australia, and Europe—yet this division is more cultural and historical than physical. Europe's boundaries are defined by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and the Ural Mountains, Ural River, Caspian Sea, and Black Sea to the east. It includes the mainland and numerous islands, covering about 10.18 million km².