Devil's Tower, formed by magma, dominates the landscape in Devil's Tower National Park, Wyoming. A timberline is formed at the base of this formation, suggesting that the terrain above is not suitable for the growth of trees.

Photograph by Bates Littlehales

  • Devils Tower is a 264-meter (867-foot) rock formation in northeastern Wyoming.

    Devils Tower is made of phonolite porphyry. Phonolite porphyry is an igneous rock, meaning it was formed as magma or lava cooled. As the magma that formed Devils Tower cooled, it condensed into columns. Most of the columns that make up Devils Tower are hexagonal (six-sided).

    Although magma formed Devils Tower, it was probably never part of a volcano. Most geologists agree that Devils Tower is an igneous intrusion, a place where magma from the Earth's mantle welled up between chunks of sedimentary rock. Devils Tower was probably formed by the same forces that created the Rocky Mountains about 65 million years ago.

    Devils Tower was not visible for millions of years. Only as water and wind slowly eroded the surrounding landscape did the igneous intrusion emerge.

    Today, the landscape continues to erode, worn away by wind, precipitation, and the nearby Belle Fourche River. However, Devils Tower is eroding, too. The base of the formation is cluttered with scree—rubble, boulders, and fragments of columns that have broken off the tower.

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  • Term Part of Speech Definition Encyclopedic Entry
    emerge Verb

    to develop or come into view.
    erode Verb

    to wear away.
    hexagon Noun

    shape having six sides.
    igneous intrusion Noun

    rock formation created by magma as it is pushed from the Earth's mantle into cracks or holes in the crust.
    igneous rock Noun

    rock formed by the cooling of magma or lava.
    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.
    magma Noun

    molten, or partially melted, rock beneath the Earth's surface.

    		 Encyclopedic Entry: Magma's Role in the Rock Cycle
    mantle Noun

    middle layer of the Earth, made of mostly solid rock.

    		 Encyclopedic Entry: mantle
    precipitation Noun

    all forms in which water falls to Earth from the atmosphere.

    		 Encyclopedic Entry: precipitation
    scree Noun

    accumulation of broken rocks, boulders, and other material at the base of cliffs or other tall rock formations.
    sedimentary rock Noun

    rock formed from fragments of other rocks or the remains of plants or animals.
    volcano Noun

    an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

    		 Encyclopedic Entry: Plate Tectonics and Volcanic Activity
    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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Photographer

Bates Littlehales

Producer

Caryl-Sue, National Geographic Society

Last Updated

Jan. 10, 2012

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