Tsunami is a Javanese word from a seismic sea wave generated by an undersea earthquake, landslide, or eruption.
Most tsunamis happen along the ring of fire. It is a zone of volcanoes and seismic activity. The zone encircles the Pasific Ocean.
Historically, tsunamis have caused much destruction and death. Since 1819, about 40 tsunamis have struck the Hawaian Islands and since 1883, about 20 tsunamis have struck Indonesia. The last one was on December 26,2004,which caused over 100.000 deaths.
A tsunami can have a width of 100 to 200 km and may spread far across the deep ocean. The speed is as fast as a jet plane. When the wave reaches land it can be very high, about 15 m or more.