March 11, 2011


The terrible earthquake that hit Japan earlier today was a magnitude 8.9. That’s one of the biggest ever recorded. The devastation caused was bad enough, but the resulting tsunami is even worse.

A tsunami used to be called a tidal wave, but that’s not a correct term. Tsunamis have nothing to do with tides - those are caused by the gravitational pull of the moon (and the sun to a lesser degree). The violent shaking of the earth underneath the ocean causes tsunamis. Tsunamis can also travel across long distances on the ocean. At sea, a tsunami wave is scarcely noticeable, but when the wave comes close to shore, it builds up and up and can by many feet high. It’s too soon at this writing to know exactly what damage has been done, but it’s likely to be very great.

For readers who want to read more about earthquakes and why we seem to have had so many big ones this year, you can read my earlier blog post:  


Photograph: The tsunami crashing into homes in Natori, Japan. Courtesy Kyodo News, via Associated Press.

Posted by: Seymour Simon

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