A series of exceptionally long, fast-moving ocean waves generated by the sudden displacement of a large volume of water, most often by an undersea earthquake but also by a volcanic eruption, submarine landslide or, rarely, a meteorite impact. In the open ocean a tsunami may be barely a foot high, but as it reaches shallow coastal water it slows and rises dramatically, sometimes to tens of feet, inundating coastlines with little warning.
Facts
PeriodicityOccurs as a series of waves, called a wave train, with periods ranging from minutes to hours between successive waves rather than at any fixed interval. 1 ScaleIntensity has been measured since the twentieth century by scales including the Sieberg-Ambraseys scale (1962), used in the Mediterranean, and the Imamura-Iida scale (1963), used in the Pacific; wave heights of tens of meters can be generated by the largest events. 1 First DescribedThe Greek historian Thucydides, writing his History of the Peloponnesian War around 426 BC, was the first to argue that tsunamis were caused by submarine earthquakes rather than by the sea itself. 1 Identification
Distinguishing AppearanceA series of waves in a body of water caused by the sudden displacement of a large volume of water, commonly by an earthquake, volcanic eruption, landslide or glacier calving, distinct from ordinary wind-driven waves or tides. 1 Connections
Associated With
Most destructive tsunamis are generated directly by large undersea earthquakes that vertically displace the seafloor and the water column above it.
A landslide entering a body of water, especially a submarine or coastal slide, can directly generate a tsunami by displacing a large volume of water, as documented at Lituya Bay in 1958.
Sources
1. Tsunami (Wikipedia)
WikipediaWikipedia 'Tsunami', lead section
a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake.
Wikipedia 'Tsunami', Scales of intensity and magnitude section
The first scales used routinely to measure the intensity of tsunamis were the Sieberg-Ambraseys scale (1962), used in the Mediterranean Sea and the Imamura-Iida intensity scale (1963), used in the Pacific Ocean.
Wikipedia 'Tsunami', History section
As early as 426 BC the Greek historian Thucydides inquired in his book History of the Peloponnesian War about the causes of tsunami, and was the first to argue that ocean earthquakes must be the cause.
Wikipedia 'Tsunami', lead section (periodicity sentence)
Tsunamis generally consist of a series of waves, with periods ranging from minutes to hours, arriving in a so-called "wave train".
Wikipedia 'Tsunami', lead section (distinguishing-appearance sentence)
a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake.
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