• moraine
    Moraines are mostly soil and rocks.

    Photograph by Jacob J. Gayer

    Moraines of Kilimanjaro
    Moraine landscapes are found all over the world and are still being formed. Glaciers in the Chugach Mountains, near the Arctic Circle in the U.S. state of Alaska, make fresh moraine deposits every day. Meanwhile, the melting snows on Tanzania's Mount Kilimanjaro are leaving fresh moraine in equatorial Africa.

    That's No Speed Bump
    Kaskawulsh Glacier in Canada has a ridge of medial moraine that stretches one whole kilometer (0.6 miles) wide.

    A moraine is material left behind by a moving glacier. This material is usually soil and rock. Just as rivers carry along all sorts of debris and silt that eventually builds up to form deltas, glaciers transport all sorts of dirt and boulders that build up to form moraines.

    To get a better idea of what moraines are, picture yourself with a toy bulldozer on a lawn that has a bunch of dry leaves all over it. When you run the bulldozer through the leaves, some of them get pushed aside, some of them get pushed forward, and some of them leave interesting patterns on the grass. Now think of these patterns and piles of pushed-away leaves—moraines—stretching for kilometers on the Earth.

    Moraines only show up in places that have, or used to have, glaciers. Glaciers are extremely large, moving rivers of ice. Glaciers shape the landscape in a process called glaciation. Glaciation can affect the land, rocks, and water in an area for thousands of years. That is why moraines are often very old.

    Moraines are divided into four main categories: lateral moraines, medial moraines, supraglacial moraines, and terminal moraines.

    Lateral Moraine

    A lateral moraine forms along the sides of a glacier. As the glacier scrapes along, it tears off rock and soil from both sides of its path. This material is deposited as lateral moraine at the top of the glacier’s edges. Lateral moraines are usually found in matching ridges on either side of the glacier. The glacier pushes material up the sides of the valley at about the same time, so lateral moraines usually have similar heights.

    If a glacier melts, the lateral moraine will often remain as the high rims of a valley.

    Medial Moraine

    A medial moraine is found on top of and inside an existing glacier. Medial moraines are formed when two glaciers meet. Two lateral moraines from the different glaciers are pushed together. This material forms one line of rocks and dirt in the middle of the new, bigger glacier.

    If a glacier melts, the medial moraine it leaves behind will be a long ridge of earth in the middle of a valley.

    Supraglacial Moraine

    A supraglacial moraine is material on the surface of a glacier. Lateral and medial moraines can be supraglacial moraines. Supraglacial moraines are made up of rocks and earth that have fallen on the glacier from the surrounding landscape. Dust and dirt left by wind and rain become part of supraglacial moraines. Sometimes the supraglacial moraine is so heavy, it blocks the view of the ice river underneath.

    If a glacier melts, supraglacial moraine is evenly distributed across a valley.

    Ground Moraine

    Ground moraines often show up as rolling, strangely shaped land covered in grass or other vegetation. They don’t have the sharp ridges of other moraines. A ground moraine is made of sediment that slowly builds up directly underneath a glacier by tiny streams, or as the result of a glacier meeting hills and valleys in the natural landscape. When a glacier melts, the ground moraine underneath is exposed.

    Ground moraines are the most common type of moraine and can be found on every continent.

    Terminal Moraine

    A terminal moraine is also sometimes called an end moraine. It forms at the very end of a glacier, telling scientists today important information about the glacier and how it moved. At a terminal moraine, all the debris that was scooped up and pushed to the front of the glacier is deposited as a large clump of rocks, soil, and sediment.

    Scientists study terminal moraines to see where the glacier flowed and how quickly it moved. Different rocks and minerals are located in specific places in the glacier’s path. If a mineral that is unique to one part of a landscape is present in a terminal moraine, geologists know the glacier must have flowed through that area.

  • Term Part of Speech Definition Encyclopedic Entry
    bulldozer Noun

    vehicle used for moving large obstacles, such as boulders or trees.

    debris Noun

    remains of something broken or destroyed; waste, or garbage.

    delta Noun

    the flat, low-lying plain that sometimes forms at the mouth of a river from deposits of sediments.

    Encyclopedic Entry: delta
    deposit Verb

    to place or deliver an item in a different area than it originated.

    end moraine Noun

    material deposited at the end of a glacier. Also called a terminal moraine.

    geologist Noun

    person who studies the physical formations of the Earth.

    glaciation Noun

    process of a glacier carving out a landscape.

    glacier Noun

    mass of ice that moves slowly over land.

    Encyclopedic Entry: glacier
    ground moraine Noun

    materials such as earth and gravel deposited by a glacier as it retreats.

    hill Noun

    land that rises above its surroundings and has a rounded summit, usually less than 300 meters (1,000 feet).

    Encyclopedic Entry: hill
    lateral moraine Noun

    material deposited at the edges of a glacier.

    lawn Noun

    area of grass mowed, watered, and maintained by people.

    medial moraine Noun

    material that is built up where two glaciers meet to form a new glacier.

    mineral Noun

    inorganic material that has a characteristic chemical composition and specific crystal structure.

    moraine Noun

    material, such as earth, sand, and gravel, transported by a glacier.

    Encyclopedic Entry: moraine
    rain Noun

    liquid precipitation.

    Encyclopedic Entry: rain
    ridge Noun

    long, narrow elevation of earth.

    river bed Noun

    material at the bottom of a river.

    rock Noun

    natural substance composed of solid mineral matter.

    sediment Noun

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

    Encyclopedic Entry: sediment
    silt Noun

    small sediment particles.

    Encyclopedic Entry: silt
    soil Noun

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

    supraglacial moraine Noun

    material that builds up on the surface of a glacier.

    terminal moraine Noun

    material deposited at the end of a glacier. Also called an end moraine.

    unique Adjective

    one of a kind.

    valley Noun

    depression in the Earth between hills.

    vegetation Noun

    all the plant life of a specific place.

    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.

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