A tsunami is a giant wave or series of waves caused by a huge earthquake or volcanic eruption under the ocean. These occur from movement in the Earth’s crust.

The earthquake causes a large amount of water to be displaced very quickly. When this happens far out at sea, tsunami waves don’t increase in height as they travel inland; the speed and size of the waves increase.

This can cause huge damage when the wave of water reaches the shoreline. You might have heard about some tsunamis in the news.

Several things happen when a tsunami hits land. First, a tsunami’s trough (the lowest point under its crest) usually reaches the shore. When it does go land, it sucks the coastal water towards the sea, exposing sea floors in the process as part of a vacuum effect.

It’s important to remember that a tsunami is a series of waves, not just one wave; this is called a ‘wave train.’ This means you should not assume that a tsunami has passed after one initial wave. Instead, it would help if you waited for official confirmation from the authorities that it is safe.

How tsunami waves happen:

  1. They usually start with an earthquake below the ocean’s surface.
  2. A series of waves travel through the deep water.
  3. As the waves travel through shallower water near land, they get bigger.
  4. The waves hit the coastline at high speeds and can cause large amounts of damage.

Tsunamis are sometimes referred to as tidal waves, but this isn’t technically correct, as tides do not cause them. A tidal wave is a shallow water wave caused by how gravity interacts between the sun, the moon, and the earth. A tsunami is a wave triggered by large ocean earthquakes, volcanic eruptions, or landslides.

Tsunami facts for kids

Now you know what a tsunami is, we’ve collated some interesting tsunami facts around them for you and your class.

  • Tsunami is a Japanese word that means ‘Harbour Wave.’
  • Approximately 80% of tsunamis happen inside the Pacific Ocean’s ‘Ring of Fire.
  • An earthquake or volcano could cause a tsunami.
  • Tsunamis can go about as fast as 500 miles (805 kilometers an hour), nearly the same speed as a jet plane.
  • Tsunamis retain their energy, allowing them to travel across vast oceans with little energy loss.
  • Hawaii is a high-risk area for tsunamis. People who live in Hawaii usually get one every year. They average a severe tsunami almost every seven years. Other vulnerable areas include Alaska and the Pacific Northwest of America.
  • Scientists can precisely predict when a tsunami will reach nearly any location in the world. They can do this using calculations for the depth of the water, distance to travel, and the time the earthquake happened to cause the tsunami.
  • If taken by a tsunami wave, you can grab a floating object and let the current carry you.
  • Tsunami waves get bigger and stronger, so the first isn’t usually the strongest.
  • Their waves can be as big as 100 feet!
  • The 2004 Indian tsunami had a 9.0 magnitude epicenter on the Richter scale.
  • That same Indian tsunami hit fourteen different countries, from Thailand to Africa, killing around 250000 people.
  • Scientists believe that a tsunami caused huge damage in Japan in 1700. They think it had a magnitude of 9.
  • A tsunami wave can be less than 30 centimeters tall!

Most deadly tsunamis:

Lisbon – 1755

The earthquake and tsunami almost destroyed Lisbon and had a death toll of between 10,000 and 100,000 people in Lisbon, making it one of the deadliest disasters in history.

Italy – 1783

The Calabrian earthquakes were a sequence of five strong earthquakes that hit the region of Calabria, the first two producing tsunamis. The death toll lies in the range of 32,000 to 50,000 people.

Italy – 1908

The Messina earthquake and tsunami took about 123,000 lives in Sicily and Calabria, southern Italy. The major cities of Messina and Reggio Calabria were almost destroyed.

Sumatra, Indonesia – 2004

This Indian Ocean earthquake and tsunami were the most devastating modern times, killing 230,000 people in 14 countries and bringing up to 30m high waves. It was the third-largest earthquake ever recorded and had the longest observed duration (8.3 to 10 minutes). Moreover, it was so strong that it caused the entire planet to vibrate.

Japan – 2011

At 2:46 pm, an 8.9 magnitude earthquake struck the northeast coast of Japan. The quake triggered a huge tsunami that swept inland. In places, the tsunami waves reached as far as 10k inland, and entire towns virtually disappeared. Japan has the longest recorded history of tsunamis in the world.

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