Tsunamis are created by earthquakes on the ocean floor. The earth’s crust is made up of many plates that always move. Where such plates meet, one of them may move on top of the other. When a plate moves upward it pushes the water above normal sea level. That is when a tsunami is born.

The energy of the earthquake creates waves that spread into all directions very quickly. In the open ocean tsunamis can reach a speed of up to 900 kilometres an hour. When a tsunami approaches the coastline it slows down to maybe 50 km an hour. The water has nowhere to go so it piles up—in some cases it gets taller than a ten-story building. It crashes onto the coast and destroys houses, beaches, roads without difficulty.

When the wave enters shallow water, it slows down and becomes taller
Image: Régis Lachaume , CC-BY-SA-3.0, via Wikimedia Commons

Tsunamis cause most damage when an underwater earthquake occurs near a coastal region. The waves can reach the coast within minutes and the population there cannot be warned in time. There is almost no way of escaping. If quakes happen very far from land it may take the killer waves a few hours to reach the coast. People can be warned and get to a safe place .

On the beach people who witness a tsunami approaching will see a great rise and fall of water. Sometimes the water near the beach will completely disappear and a few minutes later the first of the great waves can reach the shore. In some cases tsunamis don’t arrive as one big wave but as a strong flood.

People, especially tourists, often make mistakes when they see a tsunami approaching. Curious crowds stay at the beach and watch the giant waves come in. When they realize how tall these waves are, it may be too late to run. The best thing to do is to try to run as far inland as possible and try to reach high ground.

Many regions around the Pacific Ocean have warning centres and special plans on how to evacuate people when a tsunami comes close. The Pacific Tsunami Warning Centre is located on the Hawaiian islands. It detects the rise of ocean water and underwater earthquakes and reports information to many other stations in other countries. Local governments must then decide what to do.

On December 26, 2004 the world’s most powerful earthquake in 40 years occurred off the coast of Sumatra, Indonesia. The tsunami that it set into motion hit the coastal areas very quickly—during the middle of the Christmas season. Thousands of Europeans were on the beaches of Thailand, Indonesia, Sri Lanka and other islands when the tsunami hit. It is thought that about 280,000 people died . Many coastal villages were wiped out completely

Location of the 2004 Indian Ocean tsunami
Image: Uwe Dedering, CC BY-SA 3.0, via Wikimedia Commons

Village near the coast of Sumatra lies in ruins after 2004 tsunami
Image: U.S. Navy photo by Photographer’s Mate 2nd Class Philip A. McDaniel,
Public domain, via Wikimedia Commons

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Exercises

Although the ship’s owners said the Titanic was unsinkable many problems before the first voyage were overlooked. Safety regulations at that time were not very strict. The ship only had 16 life boats, enough for about 1 500 passengers. It was only tested for a few hours and never went at full speed. The telegraph system on board was new and not many people knew how to operate it.

The Titanic leaving Southampton on April 10, 1912
Image: Francis Godolphin Osbourne Stuart, Public domain, via Wikimedia Commons

During the night of April 14, 1912 the waters of the North Atlantic had a temperature of about -2° C. At noon on that day the radio operators got messages from other ships about icebergs that were nearby. The Titanic’s captain, Edward Smith, did not care about these warnings. He was captain of a steel giant that could not sink. The only thing he cared about was setting up a new world speed record. The Titanic was to be the fastest ship that ever sailed from Southampton to New York.

The night was clear and the Titanic sped on. When a big iceberg was sighted the first officer shut down all the engines. But it would have taken the ship about half a mile to come to a full stop. Even though, on the surface, the ship stayed clear of the iceberg, it ripped a big hole in the hull. At once the compartments began to flood with cold, icy water. The bulkheads were lowered but it was too late. Water flooded at least five compartments.

The collision with the iceberg was so slight that the passengers hardly heard it. Most of them didn’t take any notice and continued dancing and having fun. Some passengers were asleep in their cabins.

The bow of the ship dipped under the water’s surface and the back part of the ship began to rise. After a short time the Titanic broke into two pieces. When Captain Smith realized that the Titanic was sinking he had a distress signal sent out but the nearest ship was a hundred kilometres away.

As time went on chaos emerged and passengers rushed to the boat deck. Women and children were allowed on the lifeboats first. Lights flickered and electricity was finally gone. At 2:20 a.m. the Titanic disappeared into the Atlantic Ocean.

The Carpathia, which was the nearest ship, came to the scene about two hours later and picked up the freezing passengers in their lifeboats. By early morning the news of the disaster had gone around the world. The world’s largest ocean liner, the Titanic, had sunk on its maiden voyage, killing 1513 people.

The Titanic’s maiden voyage across the North Atlantic
Image: Prioryman, CC BY-SA 4.0, via Wikimedia Commons

Exercises

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