• stream
    Little streams turn into big rivers.

    Photograph by Chris Bligh, MyShot

    Nile v. Amazon
    The Nile and Amazon rivers have shared a long rivalry to determine which is the world's longest stream. Stretching 6,695 kilometers (4,160 miles) from its source in Burundi to its mouth in the Mediterranean Sea, the Nile is generally considered the longest. However, in 2007, a team of Brazilian scientists claimed to have found a new starting point for the Amazon River, 6,800 kilometers (4,225 miles) from its mouth.

    A stream is any body of flowing fluid. The most familiar type of stream is made of water, although streams can also be made of air, lava, electricity, or any other fluid.

    Jet streams, for instance, are cold, fast-moving winds that circulate high in the atmosphere. Lightning is a stream of electricity that circulates from cloud to cloud, from the cloud to the ground, or even from the ground to a cloud. Hydrothermal vents eject a stream of vent fluid into the ocean that surrounds them. Although vent fluid contains water, it is much, much hotter than the water surrounding it, and filled with materials from the Earth's crust, such as sulfur, zinc, and copper. Vent fluid is sometimes visible as white or black streams pouring from the vent.

    Still, the most familiar type of stream is made of free-flowing water. These streams are fed by rain, melting snow and ice, and groundwater—the water that penetrates deeper into the Earth after the surface soil is completely soaked. Streams vary in size from tiny rills or streamlets, to larger brooks, creeks, and rivers. The term “stream” is often used interchangeably with “river,” though “stream” usually refers to a smaller body of water.

    Streams take on different shapes depending on the landscape through which they flow. Cascades, or waterfalls, are formed when shallow water flows over and around large rocks. Normally, waterfalls are found in mountainous areas.

    A stream containing large amounts of sediment lining its bottom and sides can change its shape and develop large curves called meanders. Sometimes, meanders are so wide that they eventually are cut off from the main stream. The U-shaped body of water left behind is called an oxbow lake.

    Large amounts of sediment in a stream may cause it to split into many intertwined channels, called braided channels. Braided rivers are different from meandering streams. While meandering streams find a single new channel, braided streams flow over a series of wide, shallow channels.

    Human engineering efforts can change the flow of a stream. For example, a meander might be straightened to improve a shipping channel.

    Multiple streams can flow together so that one stream eventually carries water that originated from different parts of a large area. This area is known as the stream’s drainage basin, or watershed. The Amazon River in South America is the world’s largest stream and also has the world’s largest drainage basin. At more than 6.9 million square kilometers (2.3 million square miles), it is nearly as large as the entire country of Australia.

  • Term Part of Speech Definition Encyclopedic Entry
    air Noun

    the layer of gases surrounding Earth.

    Encyclopedic Entry: air
    Amazon River Noun

    (6,280 kilometers/3,900 miles) longest river in South America.

    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    braided river Noun

    flowing body of water separated into channels by tiny islands.

    brook Noun

    small flow of water, larger than a rill but smaller than a river.

    cascade Noun

    shallow waterfall over rocks.

    channel Noun

    deepest part of a shallow body of water, often a passageway for ships.

    circulate Verb

    to move around, often in a pattern.

    cloud Noun

    visible mass of tiny water droplets or ice crystals in Earth's atmosphere.

    Encyclopedic Entry: cloud
    copper Noun

    chemical element with the symbol Cu.

    creek Noun

    flowing body of water that is smaller than a river.

    crust Noun

    rocky outermost layer of Earth or other planet.

    Encyclopedic Entry: crust
    drainage basin Noun

    an entire river system or an area drained by a river and its tributaries. Also called a watershed.

    earth Noun

    soil or dirt.

    eject Verb

    to get rid of or throw out.

    electricity Noun

    set of physical phenomena associated with the presence and flow of electric charge.

    engineering Noun

    the art and science of building, maintaining, moving, and demolishing structures.

    fluid Noun

    material that is able to flow and change shape.

    groundwater Noun

    water found in an aquifer.

    Encyclopedic Entry: groundwater
    hydrothermal Adjective

    related to hot water, especially water heated by the Earth's internal temperature.

    ice Noun

    water in its solid form.

    Encyclopedic Entry: ice
    jet stream Noun

    winds speeding through the upper atmosphere.

    Encyclopedic Entry: jet stream
    landscape Noun

    the geographic features of a region.

    Encyclopedic Entry: landscape
    lava Noun

    molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

    lightning Noun

    sudden electrical discharge from clouds.

    Encyclopedic Entry: lightning
    meander Noun

    large curve in a lake or stream.

    ocean Noun

    large body of salt water that covers most of the Earth.

    Encyclopedic Entry: ocean
    oxbow lake Noun

    lake formed from an abandoned bend in a river.

    Encyclopedic Entry: oxbow lake
    penetrate Verb

    to push through.

    rain Noun

    liquid precipitation.

    Encyclopedic Entry: rain
    rill Noun

    very small stream.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    sediment Noun

    solid material transported and deposited by water, ice, and wind.

    Encyclopedic Entry: sediment
    shipping channel Noun

    deep waterway where large boats regularly transport goods and people.

    snow Noun

    precipitation made of ice crystals.

    soil Noun

    top layer of the Earth's surface where plants can grow.

    stream Noun

    body of flowing fluid.

    sulfur Noun

    chemical element with the symbol S.

    vent Noun

    crack in the Earth's crust that spews hot gases and mineral-rich water.

    visible Adjective

    able to be seen.

    waterfall Noun

    flow of water descending steeply over a cliff. Also called a cascade.

    Encyclopedic Entry: waterfall
    watershed Noun

    entire river system or an area drained by a river and its tributaries.

    Encyclopedic Entry: watershed
    wind Noun

    movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

    zinc Noun

    chemical element with the symbol Zn.

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