John Elgin, age 12, of Portland, Ore., for his question:
HOW LARGE IS THE INDIAN OCEAN?
The Indian ocean is the third largest ocean in the world. It covers about 29 million square miles. It is less than half as large as the Pacific Ocean and somewhat smaller than the Atlantic Ocean.
You'll find that the Indian Ocean extends from Africa on the west to Australia and Indonesia on the east. Asia lies to the north and Antarctic to the south.
The ocean is about 6,200 miles wide between the southern points of Africa and Australia. It narrows toward the north. There, India and the island country of Sri Lanka divide the ocean into the Arabian Sea and the Bay of Bengal.
The Indian Ocean has an average depth of 12,785 feet and is 25,344 feet deep at its deepest known point.
Since early times, the Indian ocean has been an important trade route. For many years the Arab, Chinese and Indian traders navigated the Indian Ocean. In 1498, the Portuguese explorer Vasco Da Gama sailed across the ocean after rounding the southern tip of Africa.
After the Suez Canal opened in 1869, the Indian Ocean became the most direct shipping route between Europe and the Far East.
The Sunda Islands of Indonesia separate the Indian and Pacific Oceans. Water passages through these islands include the Strait of Malacca, the Sunda Strait and the Timor Sea.
The Atlantic and Indian Oceans meet off the southern tip of Africa. The tropical waters of the Indian Ocean meet the cold waters of the Antarctic ocean in a region called the Antarctic Convergence, at about 50 degrees south latitude.
The Suez Canal links the Red Sea, an arm of the Indian Ocean, with the Mediterranean Sea. Major Indian ocean ports include Aden, Bombay, Calcutta, Colombo and Rangoon in Asia; Perth in Australia; and Durban and Dar es Salaam in Africa.
Most areas of the Indian Ocean, especially the central and northern regions, have a tropical climate. This climate makes most of the Indian Ocean almost free of icebergs, heavy fog and other navigation hazards.
Temperatures of the surface of the Indian Ocean vary widely between January and July. But they do not reach the extremes of heat and cold found in the Atlantic and Pacific. The smaller size of the Indian ocean and its almost wholly tropical and landlocked locations, prevent such temperature extremes.
The Indian Ocean has three belts of winds called the monsoons, the southeast trade winds and the prevailing westerly winds.
The tides of the Indian ocean vary greatly, but not as much as those of the Atlantic or Pacific. The Indian Ocean's smaller size probably accounts for its moderate tidal variations. The highest and lowest tides occur along the western coast of Australia. The tide rises 36 feet at Collier Bay, near Derby, but only about two feet at Fremantle.
The Indian ocean is rich in fish and shellfish.