Tsunamis are a series of massive waves generated by an underwater disturbance such as an earthquake, landslide, volcanic eruption or meteorite. Tsunamis can travel for thousands of kilometers.  As the wave approaches shallow water, it slows down and increases in height. Unlike normal cresting waves, they hit the shoreline with a large plateau of water behind them.

The impact of a tsunami is so forcefull that houses can be demolished, vehicles flipped, large objects such as ships can be carried several kilometers inland before a tsunami subsides.

Australian Council of State Emergency Services 2013