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.

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

massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.

tsunami
Noun

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

Noun

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

wave
Noun

moving swell on the surface of water.

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