A tsunami (plural: tsunamis or tsunami; from
Japanese, is a series of water waves caused by
the displacement of a large volume of a body
of water, generally 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 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 term tsunami comes from the Japanese, composed of the
two kanji (tsu) meaning "harbour" and (nami), meaning "wave".
Tsunami are sometimes referred to as tidal waves, which are
unusually high sea waves that are triggered especially by
While Japan may have the longest recorded
history of tsunamis, the sheer destruction caused
by the 2004 Indian Ocean earthquake and
tsunami event mark it as the most devastating of
its kind in modern times, killing around 230,000
people. The Sumatran region is not unused to
tsunamis either, with earthquakes of varying
magnitudes regularly occurring off the coast of
Tsunami can be generated when the sea floor
abruptly deforms and vertically displaces the
overlying water. Tectonic earthquakes are a
particular kind of earthquake that are associated
with the Earth's crustal deformation; when these
earthquakes occur beneath the sea, the water
above the deformed area is displaced from its
Tsunami can be generated when the sea floor abruptly deforms
and vertically displaces the overlying water. Tectonic earthquakes
are a particular kind of earthquake that are associated with the
Earth's crustal deformation; when these earthquakes occur
beneath the sea, the water above the deformed area is displaced
from its equilibrium position.
A tsunami cannot be precisely predicted, even if the
magnitude and location of an earthquake is known.
Geologists, oceanographers, and seismologists
analyse each earthquake and based on many factors
may or may not issue a tsunami warning. However,
there are some warning signs of an impending
tsunami, and automated systems can provide
warnings immediately after an earthquake in time to
save lives. One of the most successful systems uses
bottom pressure sensors, attached to buoys, which
constantly monitor the pressure of the overlying
Japan earthquake and tsunami of 2011, also called Great Sendai
Earthquake or Great Tōhoku Earthquake, severe natural disaster that
occurred in northeastern Japan on March 11, 2011. The event began
with a powerful earthquake off the northeastern coast of Honshu,
Japan’s main island, which caused widespread damage on land and
initiated a series of large tsunami waves that devastated many coastal
areas of the country, most notably in the Tōhoku region (northeastern
Honshu). The tsunami also instigated a major nuclear accident at a
power station along the coast.
Tsunamis are caused by an underwater earthquake, a
volcanic eruption, an sub-marine rockslide, or, more
rarely, by an asteroid or meteoroid crashing into in the
water from space. Most tsunamis are caused by
underwater earthquakes, but not all underwater
earthquakes cause tsunamis - an earthquake has to be
over about magnitude 6.75 on the Richter scale for it
to cause a tsunami. About 90 percent of all tsunamis
occur in the Pacific Ocean.
The Word Tsunami:
The word tsunami comes from the Japanese word meaning
"harbor wave." Tsunamis are sometimes incorrectly called
"tidal waves" -- tsunamis are not caused by the tides (tides
are caused by the gravitational force of the moon on the
sea). Regular waves are caused by the wind.
The Development of a Tsunami:
A tsunami starts when a huge volume of water is quickly shifted.
This rapid movement can happen as the result of an underwater
earthquake (when the sea floor quickly moves up or down), a rock
slide, a volcanic eruption, or another high-energy event.