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Tsunamis race across the sea at up to 500 miles (805 kilometers) an hour

A tsunami is a series of ocean waves that sends surges of water, sometimes reaching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widespread destruction when they crash ashore.These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries. When the ocean floor at a plate boundary rises or falls suddenly it displaces the water above it and launches the rolling waves that will become a tsunami.

If you read nothing else (beyond the article and this post), please read the “The Seismic Future of Cities (pdf),” a 2009 paper by  Roger Bilham of the University of Colorado, who just  returned from Haiti and has been roaming the world weighing which cities are most in harm’s way. (Dr. Bilham also wrote an opinion piece on bad construction in quake zones, focused on Haiti, that ran in Nature last week.) He is part of a Greek chorus of  seismologists and earthquake engineers who have been warning for a long time that some of the world’s biggest, fastest-growing cities are “ rubble in waiting,” given the haphazard rush of construction of apartments and workplaces for mainly poor new residents.

The stark reality is that, while earthquakes often capture our attention case by case, we have entered an age where population density and persistent poverty are putting enormous numbers of people in harm’s way.

How do volcanic eruptions generate tsunamis?How do submarine landslides, rock falls and underwater slumps generate tsunamis?