A tsunami (pronounced tsoo-nam-ee) is a chain of fast moving waves caused by sudden trauma
in the ocean. They can be generated by earthquakes, volcanic eruptions, or even the impact of meteorites.
Tsunamis are what we used to call tidal waves.They are most common around the edge of the Pacific, where more than half of the world's
volcanoes are found. These surges can assault coastlines, often with little or no warning. Rocks weighing as much as 20 metric
tonnes have been plucked from sea walls and carried 180m inland.
Tsunamis aren't like wind-generated waves that roll onto
a beach. A tsunami can have a wavelength (ie distance between wave crests) in excess of 60 miles (100km) and there may be
an hour between them. They travel at great speeds across an ocean with hardly any energy losses and are barely noticeable
out at sea.
Over the deep Pacific Ocean, a tsunami travels at about
500mph (800kph). If an earthquake happened in Los Angeles, a tsunami could hit Tokyo quicker than you could fly between the
cities by jet.
As a tsunami leaves the deep water of the open ocean and
travels into the shallower water near the coast, it behaves like a normal wave - only with more muscle.
Shallow water slows the tsunami and its height grows. Tsunamis
batter the coast with tremendous amounts of energy. They can strip sand from beaches, tearing up trees, and even obliterating
whole towns. Some have been known to reach as much as 30m above sea level.
