Indian Ocean - Geography.

Indian Ocean - Geography. Indian Ocean, third largest of Earth's five oceans, bounded on the west by Africa, on the north by Asia, on the east by Australia and the Australasian islands, and on the south by the Southern Ocean. No natural boundary separates the Indian Ocean from the Atlantic Ocean, but a line 4,000 km (2,500 mi) long on the 20th meridian east of Greenwich, connecting Cape Agulhas at the southern end of Africa with Antarctica, is generally considered to be the boundary. The total area of the Indian Ocean is 68.5 million sq km (26.5 million sq mi). The ocean narrows toward the north and is divided by the Indian peninsula into the Bay of Bengal on the east and the Arabian Sea on the west. The Arabian Sea sends two arms northward, the Persian Gulf and the Red Sea. The average depth of the Indian Ocean is 3,900 m (12,800 ft), or slightly greater than that of the Atlantic, and the deepest known point is 7,725 m (25,344 ft), off the southern coast of the Indonesian island of Java. In general, the greatest depths are in the northeastern sector of the ocean, where 130,000 sq km (50,000 sq mi) of the ocean floor lie at a depth of more than 5,500 m (18,000 ft). The Indian Ocean contains numerous islands, the largest of which are Madagascar and Sri Lanka. Smaller islands include the Maldive group and Mauritius. From Africa the ocean receives the waters of the Limpopo and Zambezi rivers, and from Asia those of the Irrawaddy, Brahmaputra, Ganges, Indus, and Shatt al Arab rivers. As a rule, the winds over the Indian Ocean are gentle, with frequent extended periods of calm. Tropical storms occur occasionally, however, particularly near Mauritius, and the ocean is notable for seasonal winds called monsoons. Tsunamis occur rarely in the Indian Ocean, but two of the worst in history happened there in the 19th and 21st centuries. In 1883 the eruption of the volcanic island of Krakatau resulted in a tsunami that killed 34,000 people in Java and Sumatra, and in 2004 an undersea earthquake and a resulting tsunami killed more than 135,000 people, mostly in Indonesia, Sri Lanka, Thailand, and India. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.