Download Tsunamis - LsSharks

Tsunamis
classroom.frontrowed.com/
Tsunamis have caused significant environmental damage and human devastation. A tsunami is a sudden, high
sea wave that can destroy coastal areas.
How a Tsunami Forms
There are a number of events that can trigger a tsunami. Earthquakes cause tectonic plates in the Earth’s crust
to shift. They make the ocean floor rise and fall. This causes the water to move upward. The force of gravity,
however, pulls it back down. This causes waves. As the waves reach more shallow water, they grow bigger. This
causes a large wall of water to crash into the shore. Waves sweep over the land, destroying everything in their
path.
A tsunami can be caused by an
earthquake below Earth’s surface.
A tsunami can also be caused if an underwater
volcano erupts. These are called submarine
volcanos. As the lava is pushed up, water is
displaced. This causes big waves. Tsunamis
can also happen due to an underwater
landslide.
People living on the coast experience tsunami destruction. The growing wall of water moves with great force. It
can be up to 35 meters tall! That is about as tall as a 10-story building! These waves can move at a speed of 500
miles per hour. As they move, they gain energy and height. Tsunamis may appear small or even go unnoticed
out in the open ocean. Once they hit shallow water though, the surge of energy causes the waves to rise
dramatically. Tsunami waves typically come in a series called a wave train. This makes them particularly
destructive.
The Ring of Fire
Tsunamis often occur in the Pacific Rim. This area is nicknamed the Ring of Fire. In fact, about 80 percent of all
tsunamis occur here. This is a geologically active region around the Pacific Ocean. There are many submarine
volcanoes and tectonic plate fault lines. This is why tsunamis are common here. Some of the deadliest tsunamis
have been in this area. They have hit places like Japan, Chile, and Indonesia.
A map of the Ring of Fire showing submarine volcanoes (dotted in red) and tectonic plate fault lines
(blue lines).
The Most Famous Tsunami
One of the most devastating tsunamis was the Indian Ocean Tsunami. It occurred on December 26, 2004. About
230,000 people lost their lives. A violent earthquake happened off the coast of Indonesia. It caused 30-meter
waves to slam the shores. The earthquake occurred when the Indian tectonic plate moved under the Burma
tectonic plate. The tsunami was so forceful. It triggered a chain reaction of tsunamis in the Indian Ocean. Waves
flooded the shore line. They destroyed everything in their path. Fourteen countries were hit by the tsunami.
Indonesia, Sri Lanka, India, and Thailand were hit the hardest. This tragedy sparked a huge relief effort. Over
$14 billion was raised to help survivors. The money helped with medical aid, cleanup, and rebuilding.
1/2
Waves from the Indian Ocean Tsunami
Tsunamis can be incredibly damaging. Entire
cities can be washed away. Relief organizations
like UNICEF provide aid to survivors. They bring
health and medical services, clean water, and
food to those in need.
Tsunami Awareness
Since the Indian Ocean Tsunami, many areas
prone to tsunamis have taken precautions.
Warning signs are posted on beaches and in
low lying areas. These signs alert people of the
dangers of tsunamis. They indicate the
appropriate response should a tsunami occur.
There are also signs to indicate evacuation
routes from the beach.
A tsunami warning sign on a beach in
Thailand
As a tsunami approaches the shore, either the
ridge or the trough of the wave can hit first.
The ridge is the top of the wave and the trough
is the bottom. If the ridge arrives first, a massive
wave will hit. Sudden flooding will occur. There
is no warning. However, if the trough arrives
first, a drawback will occur. The wave produces
a vacuum effect. It sucks water out towards the sea. The ocean floor is exposed. This is an important warning
sign of a tsunami. Beachgoers have about five minutes to get to higher ground. Recognizing and responding to
this sign of a tsunami can be the difference between life and death.
The Pacific Tsunami Warning System now exists in Hawaii. This group of scientists from 26 nations works to
identify tsunamis. Oceanographers, geologists, and seismologists collect information from Earth’s oceans.
They use seismic equipment, pressure sensors, and water level gauges to track tsunamis. They will issue a
warning if they see one coming. This gives people enough time to get to safety.
It takes a massive event in Earth’s crust to cause a tsunami. For this reason, tsunamis are quite rare. On
average, damaging tsunamis happen twice a year. Huge, ocean-wide tsunamis, like the Indian Ocean Tsunami,
occur only once every fifteen years or so. Regardless of their frequency, it is important to be aware of tsunamis.
We must be able to recognize signs of a tsunami. This is how we save lives.
2/2