Neptune's Needle

Third-largest ocean (c.28,350,000 sq mi/73,426,500 sq km), extending from S Asia to Antarctica and from E Africa to SE Australia; c.4,000 mi/6,437 km wide at the equator; has an average depth of c.11,000 ft/3,353 m. Constitutes about 20% of the world’s total ocean area.

Relationship to Other Bodies of Water

Connected with the Pacific Ocean by passages through the Malay Archipelago and between Australia and Antarctica; with the Atlantic Ocean by the expanse between Africa and Antarctica, and with the Mediterranean Sea via the Suez Canal. Its chief arms are the Arabian Sea (with the Red Sea, the Gulf of Aden, and the Persian Gulf), the Bay of Bengal, and the Andaman Sea.

Continental Shelf and Volcanic Cones

The continental shelf of the Indian Ocean is narrow. Madagascar and Sri Lanka, its largest islands, are structurally parts of their respective continents as are Socotra, the Andaman Islands, and the Nicobar Islands; the Seychelles and the Kerguelen Islands are exposed tops of submerged ridges. The Lakshadweep (Laccadives), the Maldives, and the Chagos are low coral islands, and Mauritius and Reunion are high volcanic cones.

Mid-Oceanic Ridge and Deep-sea Basins

The Mid-Oceanic Ridge, a broad submarine mountain range extending from Asia to Antarctica, divides the Indian Ocean into three major sections- the African, Antardis, and Australasian. The ridge rises to an average elevation of c.10,000 ft/3,048 m, and a few peaks emerge as islands. A large rift, an extension of the E branch of the Great Rift Valley that runs through the Gulf of Aden, extends along most of its length. The Mid-Oceanic Ridge, along with other submarine ridges, encloses a series of deep-sea basins (abyssal plains). The greatest depth (25,344 ft/7,725 m) is in the Java Trench, S of Java (Indonesia).

Waters That Flow Into the Ocean

Receives the waters of the Zambezi, Tigris and Euphrates, Indus, Ganga-Brahmaputra, and Ayeyarwady (Irawadi) rivers.

Temperature and Circulation Systems

The surface waters of the ocean are generally warm, although close to Antarctica pack ice and icebergs are found. The ocean has two water circulation systems- a regular counterclockwise S system (South Equatorial Current, Mozambique Current, West Wind Drift, West Australian Current) and a N system, the Monsoon Drift, whose currents are directly related to the seasonal shift of monsoon winds. The SW monsoon draws moisture from the Indian Ocean and drops heavy rainfall on the Indian subcontinent and SE Asia.

Economic Activity

Fishing is comparatively less developed in the Indian Ocean than in the Atlantic and Pacific oceans. Fishing activity takes place in the Arabian Sea and Bay of Bengal. The Indian Ocean has long served as a major highway for domestic and foreign commerce, sailed by Arabs, Indians, and Chinese for centuries.

Sources

Compiler

Peter Richards