A tsunami is a series of water waves caused by the
displacement of a large volume of a body of water, typically an ocean or
a large lake.
Earthquakes, volcanic eruptions and other underwater
explosions (including detonations of underwater nuclear devices),
landslides, glacier calvings, meteorite impacts and other disturbances
above or below water all have the potential to generate a tsunami.
Tsunami waves do not resemble normal sea waves, because their
wavelength is far longer. Rather than appearing as a breaking wave, a
tsunami may instead initially resemble a rapidly rising tide, and for
this reason they are often referred to as tidal waves. Tsunamis
generally consist of a series of waves with periods ranging from minutes
to hours, arriving in a so-called "wave train". Wave heights of tens of
metres can be generated by large events. Although the impact of
tsunamis is limited to coastal areas, their destructive power can be
enormous and they can affect entire ocean basins; the 2004 Indian Ocean
tsunami was among the deadliest natural disasters in human history with
over 230,000 people killed in 14 countries bordering the Indian Ocean.
The Greek historian Thucydides suggested in 426 BC that tsunamis were
related to submarine earthquakes, but the understanding of a tsunami's
nature remained slim until the 20th century and much remains
unknown[clarify]. Major areas of current research include trying to
determine why some large earthquakes do not generate tsunamis while
other smaller ones do; trying to accurately forecast the passage of
tsunamis across the oceans; and also to forecast how tsunami waves would
interact with specific shorelines.
