Earthquakes and Tsunami
An earthquake is a trembling movement of the earth's crust. These tremors are generally caused by shifts of the plates that make up the earth's surface. The movements cause vibrations to pass through and around the earth in wave form, just as ripples are generated when a pebble is dropped into water. Volcanic eruptions, rockfalls, landslides, and explosions can also cause a quake.
A tsunami (pronounced soo-NAHM-ee) is a series of huge waves that occur as the result of a violent underwater disturbance, such as an earthquake or volcanic eruption. They are sometimes mistakenly referred to as tidal waves, but tsunamis have nothing to do with the tides.