• Talk about a sea change: From 2006 (bottom) to 2009, Central Asia's vast Aral Sea dramatically retreated, with its eastern section losing about 80 percent of its water in just four years. The sea level of this already-shallow lake dropped about 16 meters (52.5 feet), while its shoreline receded up to 120 kilometers (75 miles).

    The immense body of water, which straddles Uzbekistan and Kazakhstan, was once the world's fourth-largest lake. But in the past 30 years, 60 percent of the lake and the Amu Darya (the river that traditionally feeds the lake) have been diverted to irrigate cotton crops, according to NASA's Earth Observatory.

    The Aral Sea was always a saline lake, but it has become much saltier as its waters have receded. In some places in the eastern seabed, salt flats spread for more than 100 kilometers (62 miles). Winds pick up the salt and deposit it over agricultural lands, spoiling some of the fertilized, irrigated soil. More than 40 million metric tons of dried salt have been swept into agricultural lands.

    This satellite imagery, from the European Space Agency, dramatically illustrates the Aral Sea's disappearance. With little government attention, it's likely that at least part of the sea may be gone for good, experts say.

  • Term Part of Speech Definition Encyclopedic Entry
    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    divert Verb

    to direct away from a familiar path.

    government Noun

    system or order of a nation, state, or other political unit.

    irrigate Verb

    to water.

    lake Noun

    body of water surrounded by land.

    NASA Noun

    (acronym for National Aeronautics and Space Administration) U.S. agency responsible for space research and systems.

    recede Verb

    to retreat or withdraw.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    saline Adjective

    salty.

    salt flat Noun

    large, flat expanse of earth covered by a thick layer of salt left by an evaporated saline lake or pond. Also called a playa, sink, or salt pan.

    satellite imagery Noun

    photographs of a planet taken by or from a satellite.

    sea Noun

    large part of the ocean enclosed or partly enclosed by land.

    Encyclopedic Entry: sea
    sea level Noun

    base level for measuring elevations. Sea level is determined by measurements taken over a 19-year cycle.

    Encyclopedic Entry: sea level
    shore Noun

    coast.

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