A Short Documentary on Tsunami
The term tsunami comes from two Japanese words that mean "harbor" and "wave." A tsunami is a series of large waves generated by an abrupt movement on the ocean floor that can result from an earthquake, an underwater landslide, a volcanic eruption or - very rarely - a large meteorite strike. However, powerful undersea earthquakes are responsible for most tsunamis. Seismologists say only earthquakes measuring greater than 7.0 on the Richter scale can produce a major tsunami. Most earthquakes that generate tsunamis - including Friday's jolt off Japan's eastern coast - occur in areas called subduction zones, where pieces of the Earth's crust press against each other. Subduction means that one tectonic plate slides beneath another and sinks deep into the Earth's mantle. The friction between two slow-moving plates of the Earth's crust creates vast amounts of seismic energy which is released in the form of an earthquake. When a strong underse...