What is the term for a tsunami that travels across entire ocean basins?

A tsunami that travels across entire ocean basins is called a distant tsunami. It is also known as a teletsunami, ocean-wide tsunami, or trans-ocean tsunami, and its source is typically more than 1,000 kilometers from the affected coast.

Distant tsunamis are usually generated by very large undersea earthquakes that cause widespread vertical movement of the seafloor. In deep water, the waves can travel at speeds approaching 800 kilometers per hour while remaining relatively low and difficult for ships to notice. As they enter shallow coastal water, they slow down and grow taller.

The 1960 Valdivia earthquake in Chile produced a teletsunami that crossed the Pacific and caused severe damage in Hawaii and impacts as far away as Japan and the Philippines. The 2004 Indian Ocean tsunami is another major example of a trans-ocean event.

“ Tidal wave” is a misleading nickname: tides are driven mainly by the Moon and Sun, while tsunamis result from sudden displacement of water. A local tsunami, by contrast, begins near the coast and arrives much sooner.