What caused Japan's tsunami?

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PHOENIX – The tsunami that caused so much destruction when it hit Japan Friday morning was caused by the seventh worse earthquake on record, registering 8.9 on the Richter scale. 

That earthquake happened on the ocean floor more than 200 miles from Tokyo. Arizona State University professor of earthquake geology Ramon Arrowsmith says sections of the ever-moving earth's crust, known as plates, began to lift after colliding. 

Arrowsmith says that energy gave birth to huge waves on the ocean's surface. Those waves became tsunamis when the crashed ashore in Japan.

While Friday’s horrific destruction caused by the quake and tsunami may seem a once-in-a lifetime disaster to us, Professor Arrowsmith says it's nature's way and has happened often in the past and will happen again in the future.