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An underwater volcanic eruption can also
trigger a tsunami. If an earthquake occurs underwater, the energy
generated by it is carried by water in the form of a series of waves
that have been named tsunami. The energy that they carry makes them
very powerful and they sweep off everything in their path. If they
occur in deep oceans, the water will not be able to rise much. But
it is when they are nearer the coasts that giant destructive waves
are formed.
Some tsunamis have reached a height of 100 feet. Tsunamis have
occurred in Japan, Indonesia and Nicaragua. Most tsunamis occur in
the area identified as the Ring of Fire. This is a seismic activity
prone area that encircles the Pacific Ocean. The Hawaiian Islands
fall in this area and 40 tsunamis have been known to have hit the
islands since 1819.
Can a tsunami be predicted?
Predicting or even detecting a tsunami is very difficult. When it
begins, usually in deep waters, it looks very deceptively like any
other gentle normal sea movement. And once it gathers momentum, it
is a matter of minutes before it reaches ashore. Whenever an
earthquake measuring more than 6.75 on the Richter scale occurs,
observers set up watches for tsunamis.
A few harrowing instances
The 2004 Tsunami - The 2004 Indian Ocean earthquake, an undersea earthquake that
occurred on December 26, 2004 triggered a series of deadly tsunamis
that spread throughout the Indian Ocean, killing huge numbers of
people and devastating coastal communities in Indonesia, Sri Lanka,
India, Thailand, and other countries. Over 280,000 people are
estimated to have perished due to these Tsunamis and it is one the
worst natural disasters in recorded history.
A tsunami that struck Honshu, Japan in 1896 had actually passed
beneath the boats of a few anglers who were at sea. They could never
guess that the gentle wave that passed them would take on monstrous
proportions. It left 28,000 people dead on the coast and destroyed
170 miles of coastline. The anglers who had been at sea returned
safe to a destroyed coastal town.
In April 1946, at Hilo in Hawaii, a wave that had traveled all the
way from Alaska, a good 2,500 miles, struck and left several dead
and property worth millions destroyed.
In 1958 in Alaska, a tsunami traveled 1,700 feet up a hillside and
totally wiped out plant life there. The sequence of events was first
an earthquake, then a landslide caused by the tremors and then the
resultant tsunami.
Even when it is possible to issue a tsunami warning, the tsunami
generally hits minutes after the warning, rendering it pointless.
And as it is a series of waves, often the first one is generally
gentle and the waves get forceful progressively. So people are
advised to stay away from the danger area for a while until the
danger passes. A tsunami that originated in the Pacific Ocean in
1960 in the wake of a massive earthquake in the coastal area of Isla
Chiloe, Chile, traveled for fifteen hours and then struck Hawaii. |
