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All about Oceans and Current Environmental Issues

written by: Terrie Schultz•edited by: Jason C. Chavis•updated: 6/10/2010

Oceans cover 70% of Earth's surface, and 97% of the world's water is in the oceans. Learn facts about oceans and some of the critical environmental issues that are of grave concern today.

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    Facts About the World's Oceans

    Here are some important facts about oceans to know around the world:

    • Atlantic- separating the Americas from the European and African continents, the Atlantic Ocean covers 21% of Earth's surface and has an average depth of 10,800 feet. Several shallow seas are part of the Atlantic Ocean, including the Caribbean, Mediterranean and Gulf of Mexico. Some of the major rivers that drain into the Atlantic include the Amazon, Congo, Mississippi and St. Lawrence.
    • Pacific- the world's largest ocean, the Pacific covers 64 million square miles, or approximately 30% of Earth's surface. It is also the deepest ocean with an average depth of 14,000 feet, and it is the location of the 35,840 foot deep Mariana Trench, the deepest point on Earth. There are some 25,000 islands in the Pacific, many of which were formed by volcanic eruptions. Some of the rivers that drain into the Pacific include the Colorado, Columbia, Rio Grande de Santiago, Mekong and Yukon.
    • Arctic- the Arctic Ocean is the smallest and shallowest of the five oceans. It accounts for only 3% of Earth's surface and has an average depth of 3,450 feet. The center of the Arctic Ocean is covered by a layer of sea ice up to 10 feet thick. In the winter, most of the surface of the Arctic Ocean is covered by sea ice, while in the summer the ice coverage is reduced by half.
    • Indian- the Indian Ocean is bordered on the west, north and east by Africa, Asia and Australia respectively, and on the south merges with the Southern Ocean. It covers about 14% of the surface of the Earth, and is the world's warmest ocean. The Indian Ocean has an average depth of 12,800 feet, and the 23,812 foot deep Java Trench is located there. Some of the rivers that discharge into the Indian Ocean include the Ganges, Indus, Irrawaddy and Zambezi.
    • Southern- the Southern Ocean encircles Antarctica. It ils the second smallest ocean, covering only 4% of Earth's surface, but unlike the shallow Arctic Ocean, its depth ranges from 13,100-16,400 feet, and it also contains the 23,737 foot deep South Sandwich Trench. Several seas are part of the Southern Ocean, including the Amundsen Sea, Ross Sea, Scotia Sea and Weddell Sea. The Southern Ocean is partially covered with sea ice, with the amount of ice fluctuating by season.

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    Current Environmental Facts about Oceans

    There are many environmental issues threatening the world's oceans and putting marine organisms at risk. Here are a few of the most severe problems facing the oceans today.

    • Acidification- Carbon dioxide from the air is absorbed by ocean water and reacts to become carbonic acid, causing the pH of the ocean water to decrease. Overly acidic water is detrimental to many marine organisms, particularly those with shells.
    • Pollution- Plastic trash from mainland sources and ocean-going vessels litters the shores and collects in vortexes such as the one known as the Great Pacific Garbage Patch, creating a serious threat to marine birds and animals, many of which consume or get tangled in it. Toxins in the plastic are also released into the water. Pollutants including pesticides, sewage and detergents are discharged into the oceans where they may poison marine life directly or accumulate in the food chain. Runoff from chemical fertilizer causes an overgrowth of algae, which in turn depletes the dissolved oxygen, resulting in ocean dead zones where fish and marine animals cannot survive. Oil spills coat birds and animals and destroy marine ecosystems.
    • Overfishing- many species of fish have been driven nearly to extinction by overfishing.
    • Habitat destruction- coastal development, draining wetlands and swamps, dredging, logging and the building of dams are some of the ways that ocean habitat is devastated.

    These and more are the environmental issues that are putting a severe burden on the world's oceans. While the oceans are vast, they are not infinite, and there will be a point at which they will not be able to recover if these destructive practices are not stopped.

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    Sources

    Michael Pidwirny and J. Emmett Duffy. 2010. "Ocean." Encyclopedia of Earth.

    Ocean Facts. See the Sea

    "Critical Ocean Issues." National Geographic.