The average northern limit of icebergs is 45 deg south latitude. Fishing is confined to subsistence levels. The ocean's most important function has been that of trade transport. Europeans, following the ancient seafarers, had crossed its waters to reach the East and returned with silks, rugs, tea, and spices. The Indian Ocean is also noted for its role in the shipment of petroleum from Southeast Asia to the West.
Petroleum is the most significant mineral of the area, extracted primarily on the Persian Gulf.
The earliest known civilizations, in the valleys of the Nile, Euphrates, Tigris, and Indus rivers and in Southeast Asia, have developed near the Indian Ocean. Returning ships brought gold and slaves. Phoenicians of the 3d millennium BC may have entered the area, but no settlements resulted. Vasco da GAMA rounded the Cape of Good Hope in 1497 and sailed to India, the first European to do so. The ancient peoples who lived along the ocean each tried unsuccessfully to control its commercial routes.