The World Ocean and Ocean Currents

The World Ocean covers about 71% of the Earth's surface. The movement of ocean water has a great influence on climate.

Oceans

• There are four oceans: the Pacific, the Atlantic, the Indian, and the Arctic.
• The Pacific Ocean is the largest and the deepest. The Arctic Ocean is the smallest and the shallowest.
• The deepest place: the Mariana Trench (Pacific Ocean, about 11 km).
• The average salinity of water is about 35‰. The Red Sea (about 41‰) is among the saltiest, while the Baltic Sea has low salinity.

Ocean currents

Causes: constant winds, the Earth's rotation, temperature differences.

Warm currents	Cold currents
Gulf Stream (Atlantic)	Peru
Kuroshio (Pacific)	Benguela
Brazil	Labrador
	California

• The Gulf Stream: a warm current, in the Atlantic. It moderates the climate of North-Western Europe.
• Peru and Benguela: cold currents. Deserts form beside cold currents: the Atacama beside the Peru Current, the Namib beside the Benguela Current.

Tides and waves

• The rise and fall of the tides occur under the influence of the gravitational pull of the Moon and the Sun.
• Tsunamis are caused by undersea earthquakes, not by the Moon's gravitational pull.