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The Deadliest Tsunami in History?
National Geographic News
Updated January 7, 2005
Tsunamis: Facts About Killer Waves
The earthquake that generated the great Indian Ocean tsunami of
2004 is estimated to have released the energy of 23,000 Hiroshimatype atomic bombs, according to the U.S. Geological Survey
(USGS).
Giant forces that had been building up deep in the Earth for
hundreds of years were released suddenly on December 26, shaking
the ground violently and unleashing a series of killer waves that sped
across the Indian Ocean at the speed of a jet airliner.
By the end of the day more than 150,000 people were dead or
missing and millions more were homeless in 11 countries, making it
perhaps the most destructive tsunami in history.
The epicenter of the 9.0 magnitude quake was under the Indian
Ocean near the west coast of the Indonesian island of Sumatra,
according to the USGS, which monitors earthquakes worldwide. The
violent movement of sections of the Earth's crust, known as tectonic
plates, displaced an enormous amount of water, sending powerful
shock waves in every direction.
The earthquake was the result of the sliding of the portion of the
Earth's crust known as the India plate under the section called the
Burma plate. The process has been going on for millennia, one plate
pushing against the other until something has to give. The result on
December 26 was a rupture the USGS estimates was more than 600
miles (1,000 kilometers) long, displacing the seafloor above the
rupture by perhaps 10 yards (about 10 meters) horizontally and
several yards vertically. That doesn't sound like much, but the
trillions of tons of rock that were moved along hundreds of miles
caused the planet to shudder with the largest magnitude earthquake
in 40 years.
Above the disturbed seafloor the great volume of the ocean was
displaced along the line of the rupture, creating one of nature's most
deadly phenomena: a tsunami. Within hours killer waves radiating
from the earthquake zone slammed into the coastline of 11 Indian
Ocean countries, snatching people out to sea, drowning others in
their homes or on beaches, and demolishing property from Africa to
Thailand.
Tsunamis have been relatively rare in the Indian Ocean, at least in
human memory. They are most prevalent in the Pacific. But every
ocean has generated the scourges. Many countries are at risk.
(Read "Tsunami: Facts About Killer Waves" for more about killer
waves' causes and warning signs—information that can be a
lifesaver in a tsunami zone.)
The Indian Ocean tsunami traveled as much as 3,000 miles (nearly
5,000 kilometers) to Africa, arriving with sufficient force to kill people
and destroy property.
A tsunami may be less than a foot (30 centimeters) in height on the
surface of the open ocean, which is why they are not noticed by
sailors. But the powerful pulse of energy travels rapidly through the
ocean at hundreds of miles per hour. Once a tsunami reaches
shallow water near the coast it is slowed down. The top of the wave
moves faster than the bottom, causing the sea to rise dramatically.
The Indian Ocean tsunami caused waves as high as 50 feet (15
meters) in some places, according to news reports. But in many
other places witnesses described a rapid surging of the ocean, more
like an extremely powerful river or a flood than the advance and
retreat of giant waves.
Tsunamis can extend inland by a thousand feet (300 meters) or
more. The enormous force and weight of so much water sweeps
away almost everything in its path. As many as a third of the people
who died in the Indian Ocean tsunami were children; many of them
would not have been strong enough to resist the force of the water.
The Deadliest Tsunami in History?
National Geographic News
Updated January 7, 2005
Many people were crushed by debris or when the sea hurled them
against structures.
high ground minutes before the tsunami arrived. Very few animal
bodies were found afterwards.
Witnesses said the approaching tsunami sounded like three freight
trains or the roar of a jet. In some places the tsunami advanced as a
torrent of foaming water.
When the ocean started to return on December 26 it was in the form
of the tsunami—a series of crashing waves in some places and a
sudden flood hundreds of yards inland in others. Reports quoted
survivors saying they could not run away fast enough, although
many people did manage to escape.
In several places the tsunami announced itself in the form of a
rapidly receding ocean. Many reports quoted survivors saying how
they had never seen the sea withdraw such a distance, exposing
seafloor never seen before, stranding fish and boats on the sand.
Tragically the novelty of the sight apparently stoked the curiosity of
the people who ran out onto the exposed seafloor. Tourists in
Thailand were seen wandering around photographing the scene.
Geographic Knowledge Saved Lives
People who knew geography knew what the receding ocean meant.
Survivors who knew it meant trouble reported how they ran for high
ground, rounded up family and friends, and tried to warn people who
were drawn to the water's edge. Experts say that a receding ocean
may give people as much as five minutes' warning to escape to high
ground. That may have been enough time for many of the people
who were killed by the 2004 tsunami to save themselves, if only they
knew what to do.
A British newspaper reported that a school student, on vacation in
Thailand, recalled a geography lesson about tsunamis and what the
withdrawal of the ocean meant. She warned her family and they
saved themselves.
In India a man told the Associated Press how he saved his village of
some 1,500 people because he recalled watching a National
Geographic television documentary about tsunamis [Killer Wave],
and remembered that when the ocean receded it was a sign of
danger. He sounded the alarm and led the people to high ground,
saving almost the entire village.
Somehow the animals also seemed to know that disaster was
imminent. Many people reported that they saw animals fleeing for
Death struck randomly. People who were together when the tsunami
struck were separated in the torrent. Some survived; others
succumbed or disappeared. A baby was found floating safely on a
mattress.
Survivors of the Indian Ocean tsunami reported that the sea surged
out as fast and as powerfully as it came ashore. Many people who
had survived the wall of water rushing inland were seen being swept
out to sea when the ocean retreated.
A tsunami is a series of waves, and the first wave may not be the
most dangerous. A tsunami "wave train" may come as surges five
minutes to an hour apart. The cycle may be marked by repeated
retreat and advance of the ocean. Some people did not know this on
December 26. Once the first wave had gone, they thought it was
safe to go down to the beach.
The Indian Ocean tsunami destroyed thousands of miles of coastline
and even submerged entire islands permanently. The island country
Maldives rises only a few feet above sea level, but it is largely
protected by outlying coral reefs. Even so, the tsunami swept across
the reefs and was reported to have washed over some islands
entirely. The capital and many tourist resorts in the Maldives were
flooded. Astonishingly, relatively few people were killed. The country
was likely protected from the full force of the tsunami by its reefs.
Rotting Corpses
As the day of horror drew to a close the ocean calmed. But where at
the start of the day people were going about their normal lives or
relaxing at exotic beach resorts now millions of people were
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The Deadliest Tsunami in History?
National Geographic News
Updated January 7, 2005
struggling with the reality of tens of thousands of dead or missing
relatives, destroyed homes, and shattered lives. The thousands of
corpses, many hanging in trees or washed up on beaches,
immediately started to rot in the tropical heat. With no food or clean
water and open wounds, the risk of famine and epidemic diseases
was high. Health authorities feared that the death toll might double to
300,000.
Across the world the magnitude of the disaster and the scale of the
suffering prompted a new wave—one of sympathy, support, and
assistance for the people affected by the tsunami.
Deep beneath the ocean, at the source of the great earthquake and
tsunami, the Earth's tectonic plates continued their relentless
pressing against one another. Pressure was already building for the
day when pent-up energy will once again be released violently—but
hopefully not for hundreds of years.
Questions:
1) What caused the major earthquake to occur on December 26, 2004?
2) Describe how this earthquake occurred? Refer to specific tectonic plates
in your answer.
3) How far did the Indian Ocean tsunami travel? What were the
consequences in this location?
4) Discuss how tsunamis change in height from the open ocean to the shores
of countries?
5) What affects did the Indian ocean cause?
6) Discuss how a rapidly receding ocean can either save lives or destroy
them?
7) What are some other telling signs that a tsunami is on its way?
8) What are some of the horrible results after the tsunami has finished?
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