• On September 29, 2009, a magnitude 8.1 earthquake shook the seafloor of the Pacific Ocean near the Samoan Islands. The earthquake caused a tsunami, whose 6-meter (20-foot) waves devastated the coastlines of Samoa, American Samoa, and Tonga. Nearly 200 people died.

    The Samoan Islands are located in the southern Pacific Ocean, where two tectonic plates meet. Here, the massive Pacific plate subducts beneath the smaller Indo-Australian plate. This tectonic activity has made the region—stretching from New Zealand to an area just south of the Samoan Islands—one of the most prone to earthquakes and volcanoes.

  • Term Part of Speech Definition Encyclopedic Entry
    coastline Noun

    outer boundary of a shore.

    devastate Verb

    to destroy.

    earthquake Noun

    the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.

    massive Adjective

    very large or heavy.

    prone Adjective

    vulnerable or tending to act in a certain way.

    seafloor Noun

    surface layer of the bottom of the ocean.

    subduct Verb

    to pull downward or beneath something.

    tectonic activity Noun

    movement of tectonic plates resulting in geologic activity such as volcanic eruptions and earthquakes.

    tectonic plate Noun

    large, moveable segment of the Earth's crust.

    tsunami Noun

    ocean waves triggered by an earthquake, volcano, or other movement of the ocean floor.

    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: volcano
    wave Noun

    moving swell on the surface of water.

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