The Indian Ocean is the third largest of the world’s oceans, but it is the youngest and warmest. It is bordered by Africa to the west, south Asia to the north, and the island chain of Indonesia and Australia to the east; many bays and seas spread off into those lands, including the Bay of Bengal, the Persian Gulf, and the Red Sea. Only a few major rivers empty into the Indian Ocean: the Zambezi and the Narmada in Africa, the Indus, Ganges, and Brahmaputra from the Subcontinent, and the Irrawaddy in Myanmar. It mingles with the Southern Ocean south of latitude 60°, with the Atlantic Ocean at the southern tip of Africa, and with the Pacific Ocean south of Tasmania. The Ocean has an average depth of 12,274 ft (3741 m) and a maximum depth of 25,938 ft (7906 m) and it is the least explored of all the oceans.
The Indian Ocean began to be formed about 100 million years ago as the Indian Tectonic Plate separated from southern Africa and Madagascar and began to move northwards, leaving the growing Ocean behind it. Approximately 50 million years ago, the Indian Plate reached the south edge of Asia and the Indian Ocean took on its present shape. Except for Madagascar and Sri Lanka, nearly all the islands in the Ocean are either coral atolls or volcanic seamounts. The tectonic plates in and around the Ocean and the spreading ridges between them are still active, producing volcanoes and earthquakes with some regularity.
The climate north of the equator is affected by the monsoon winds which blow from the north-east from October until May, and from the south and west from May to October. The lands along the northern arc of the Ocean depend upon the monsoons for rainfall, but severe monsoons often bring flooding to the lands bordering the Bay of Bengal and the Arabian Sea. The sea currents are mainly controlled by by the monsoon winds, and two large gyres flow across the Ocean: the one in the northern hemisphere flows clockwise and the one in the southern hemisphere flows counter-clockwise–during the winter monsoon, the northern flow is reversed.
Early Homo Sapiens left Africa about 100,000 years ago, headed east along the northern coast of the Indian Ocean, and is known to have arrived in Australia by about 50,000 years ago. Two of the great ancient civilizations, that of Mesopotamia and the Indus Valley, developed along the Ocean’s northern edge roughly 6000 years ago, and there is evidence of sea trade between them by at least 4500 years ago. Later civilizations, including the Greek, Roman, and Arab, continued to expand the maritime trade routes. These sea routes were mainly along the coastlines but the alternating monsoon winds allowed for open sea passage between Africa, Arabia, India, and Indonesia. From 1405 to 1433, the Chinese Admiral Zheng He led large ‘treasure’ fleets of the Ming Dynasty from China all the way to East Africa. In 1497, Portuguese navigator Vasco da Gama became the first European to sail to India and later the Far East. The succeeding centuries saw vigorous attempts by the Portuguese, Spanish, Dutch, French, and British to colonize the surrounding lands and profit from the resources. Today, most of the surrounding lands have become independent nations, although many of the islands of the Indian Ocean are still controlled in some way by France, the United Kingdom, and Australia (among others). The islands and island nations near to the coasts of Africa and Asia are popular tourist destinations for Europeans and Orientals, with warm waters and perfect sandy beaches inviting swimming, diving, and fishing. Islands further out in the Ocean are primarily military outposts. Many of the islands, however, are at risk from rising sea levels and it remains to be seen how long they can survive.
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Western Indian Ocean Islands
Maldives, Seychelles, Mauritius, Reunion
East African Coastal Islands
December, 2014 – January, 2015
Madagascar, Mozambique Island, Dar es Salaam, Zanzibar Island