• fold mountain
    The Himalayas keep folding, and getting taller.

    Photograph by Ziaur Rahman, MSYS

    Orogenic Infants
    Most fold mountains are very young. In fact, most fold mountains are still growing.

    Fold mountains are mountain ranges that are formed when two of the tectonic plates that make up the Earth's crust push together at their border. The extreme pressure forces the edges of the plates upwards into a series of folds.

    Fold mountains are created through a process called "orogeny." An orogenic event takes millions of years to create a mountain range because tectonic plates move only centimeters every year.

    The Earth has two different types of crust: continental crust and oceanic crust. Orogenic events can occur on both types of crust. The Himalaya Mountains are still growing as the Indian continental plate folds over the Eurasian continental plate. Orogeny can also involve oceanic plates. Beneath the microcontinent of Zealandia, the Pacific plate is being folded over the Australian plate. The result is New Zealand's Southern Alps.

    Most people think of the rugged, soaring heights of the Himalayas, Andes, and Alps when they think of fold mountains. But some of the Earth's smaller mountain ranges were once soaring peaks, too. The Appalachian Mountains started forming 480 million years ago when the North American and Eurasian continental plates collided. The Appalachians were once taller than the Himalayas. The range stretches from Newfoundland in southeastern Canada down through the eastern United States to central Alabama. However, erosion has taken its toll on the Appalachians. Today, some of its higher peaks are less than a third of the height of Everest.

    Fold mountains are the most common type of mountain on Earth. Other types of mountains are volcanic mountains, erosional mountains, and fault-block mountains. Volcanoes create volcanic mountains. Erosional mountains are created as wind and water wear away soft portions of land and leave rocky hills. Fault-block mountains are created where parts of continental crust are displaced.

  • Term Part of Speech Definition Encyclopedic Entry
    Appalachian Mountains Noun

    large mountain range stretching from southeastern Canada to the southeastern United States.

    border Noun

    natural or artificial line separating two pieces of land.

    Encyclopedic Entry: border
    continental crust Noun

    thick layer of Earth that sits beneath continents.

    crust Noun

    rocky outermost layer of Earth or other planet.

    Encyclopedic Entry: crust
    erosion Noun

    act in which earth is worn away, often by water, wind, or ice.

    Encyclopedic Entry: erosion
    erosional mountain Noun

    elevated area of Earth's crust formed by wearing away of surrounding land.

    fault-block mountain Noun

    elevated area of Earth's crust formed by movement and displacement of the crust.

    fold mountain Noun

    areas of the Earth's crust that have been bent and forced up by movement of tectonic plates.

    Encyclopedic Entry: fold mountain
    Himalaya Mountains Noun

    mountain range between India and Nepal.

    microcontinent Noun

    a type of large continental island.

    mountain range Noun

    series or chain of mountains that are close together.

    oceanic crust Noun

    thin layer of the Earth that sits beneath ocean basins.

    orogenic event Noun

    process of a specific mountain range or ranges being formed.

    orogeny Noun

    the way mountains are formed.

    tectonic plate Noun

    large, moveable segment of the Earth's crust.

    volcanic mountain Noun

    elevated area of Earth's crust formed by a volcano.

    Zealandia Noun

    a microcontinent that broke off from Australia about 80 million years ago. Zealandia is almost totally underwater.

    Encyclopedic Entry: Zealandia

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