A tsunami is a series of huge waves that can cause great devastation and loss of life when they strike a coast. Tsunamis are caused by an underwater earthquake, a volcanic eruption.
NOTE: If you see the water recede quickly and unexpectedly from a beach , run toward higher ground or inland -- there may be a tsunami coming. Also, if you are on the coast and there is an earthquake, it may have caused a tsunami, so run toward higher ground or inland. Some beaches have tsunami warning sirens . The first wave in a tsunami is often not the largest; if you experience one abnormally-huge wave. even bigger waves could be coming soon.