The world watched in horror as a tsunami caused devastation in Japan. A massive earthquake measuring 9.0 on the Richter scale hit the northeastern coastline triggering a 10m tsunami that caused extensive damage. It is the biggest recorded earthquake to hit Japan and tens of thousands of casualties are feared.
What are tsunamis?
Tsunamis are often called tidal waves. But these waves have nothing to do with the tides. They are usually caused by a submarine earthquake occurring less than 50 km below the sea floor, though they can also be caused by undersea volcanic eruptions or landslides.
Sometimes, the first sign to reach land may be not the high wave that follows, but a trough, even exposing the sea floor. In November 1755 on All Saints Day, in Lisbon, Portugal, this happened, and as many curious onlookers rushed onto the floor of the bay to inspect this curious phenomenon, they were drowned by the tidal wave that followed just minutes later. And similar phenomena have been described in this latest disaster.