What exactly is a tsunami?
A tsunami is a series of large often catastrophic ocean waves. Tsunamis should not be confused with Tidal Waves, these are waves generated on the surface of the ocean by wind, tidal pull from the moon and the position of the earth.
Why do tsunamis happen?
The large waves that form a tsunami happen when there is an earthquake under the ocean. When large slabs of rock are forced to move past each other causing the water above to move. Other things can make tsunamis too, such as volcanic eruptions, sub-marine rockslides or a large impact in the water from an asteroid or meteor. Water will move in all directions from the location of the disturbance, starting small and getting larger and larger. Waves from a tsunami can reach 100 feet and travel as far as 5,000 kilometers.
What are the effects of a tsunami?
When waves caused by the underwater disturbance reach land, they will be far faster and more powerful than regular ones. They also grow in size as they approach the shallow waters near land.
These large, powerful waves can destroy buildings, roads, railways, and pretty much anything else in their path. Tsunamis can destroy whole communities leaving many people homeless and destroying their livelihoods.
Clean drinking water will be contaminated and individuals affected often lose their possessions.
The tsunami that struck Indonesia on September 28th was triggered by a 7.5 magnitude earthquake. The on-land speed of the tsunami waves reached 100 km/h and were 20 feet high.
Click below for more information from Alf about this specific tsunami and what makes it different.