Tsunami
Tsunami,
Japanese word, meaning “harbor wave” and used as the scientific term
for seismic sea waveGenerated by an undersea
earthquake or possibly an undersea
landslide or volcanic eruption. When the Ocean floor
is tilted or offset during an
earthquake; a set of waves is created similar to the
concentric Waves generated by
an object dropped into the water. Most tsunamis
originate along the ring of fire, a
zone of volcanoes and seismic activity , 32500 km
(24,000mi) long, that encircles
the pacific ocean. Since1819, about 40 tsunamis have
struck the Hawallan islands.
A Tsunami can have wavelengths, or widths, of 100 to
200 km (60 to 120 mi), and
may travel
hundreds Of kilometers across the deep ocean, reaching speeds of
about 725 to
800 km/h (about 450 to 500 mph)
Upon entering shallow coasted wasters, the wave
which may have been only about
half a meter (a foot Or two) high out at sea,
suddenly grows rapidly. When the
wave reaches
the shore, it may be 15 m (50ft) high or more. Tsunamis have
tremendous
energy because of the great volume of water affected. They are
Capable of obliterating coastal settlements.
Tsunami should not be confused with storm surges,
which are domes of water that
rise underneath hurricanes or cyclones and cause
extensive coastal flooding when
the storms
reach land. Storm surges are particularly devastating if they occur at
high tide. A
cyclone and accompanying storm surge killed an estimated
500,000people in Bangladesh in 1970.
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