This is how a tsunami is formed

If there is an earthquake on the ocean floor, it can move a tremendous amount of water and thus cause tsunamis that hit the beaches.

If there is an earthquake on the ocean floor, it can move a tremendous amount of water and thus cause tsunamis that hit the beaches.

A tsunami turned paradise islands into hell

On Sunday morning, December 26, 2004, an earthquake hit the ocean floor off the Indonesian island of Sumatra.

The earthquake is the strongest in four decades and the energy from the earthquake corresponded to the explosive power of 23,000 nuclear bombs.

The earthquake set the enormous water mass of the ocean in motion, and a few minutes later tsunami waves up to 30 meters high hit the Indonesian city of Banda Aceh, which was closest to the epicenter.

160,000 inhabitants perished in this foaming mass of water, but the disaster was not over. Just a few hours later, huge waves hit the shores of thirteen countries and nearly 250,000 people lost their lives.

A tsunami spreads across the Indian Ocean in 2004:

On December 26, Christmas Day in 2004, a tsunami of unprecedented size and force hit 14 countries around the Indian Ocean. At least 226,000 people died. This video shows the journey of the tsunami from the epicenter near Sumatra.

How is a tsunami formed?

Tsunami is Japanese and actually means “harbor wave” and it’s no surprise that the name tsunami has Japanese roots.

Most tsunamis are caused by earthquakes, and the Asian island nation lies on the edge of three tectonic plates in one of the world’s most active seismic zones.

Tsunamis can also be created by volcanic eruptions, landslides and meteorites. The most destructive tsunami in Earth’s history was probably caused by a meteorite in the oceans millions of years ago.

This is how a tsunami is formed

When an earthquake shakes the ocean floor, it moves a huge mass of water that turns into huge waves at the beaches.

The bottom pushes water to the side

During the earthquake, the sea floor jolts upwards and pushes water to the sides away from the source area. At great depths, the waves do not rise high, but they can be hundreds of kilometers wide.

Slow on the wave

A large water wave reaches a speed of up to 1,000 km. At the coast, shallows reduce the speed, which will be around 30-40 km. The pressure sucks water from the shore and this additional volume raises the tidal wave.

The water hits the land

The entire mass of water now reaches the shore and the tidal wave can reach a height of 30 meters. It hits the beach with force and can destroy entire villages and suck it out to sea.

Regardless of the cause of the tsunami, the process behind the tsunami is the same: When large earthquakes cause the ocean floor to move up and down, the mass of water from the surface to the bottom begins to move—just like when you throw a stone into the ocean.

The movement creates eddies in the water that spread out from the center of the quake.

In the open ocean, a tidal wave is hardly noticeable, as the wave is rarely higher than half a meter due to the wavelength of several hundred kilometers.

At approximately 1000 km/h. the tidal wave travels across the ocean until it approaches land. There, the tsunami slows down to 30-40 km/h and the wavelength, which was previously spread over several kilometers, suddenly compresses.

As a result, the water is pushed upwards and rises into a vertical wall of water many meters high that hits the beaches.

Three different tsunamis

There are three different types of tsunamis: local, regional, and teletsunamis.

  • A local tsunami has a destruction radius of up to 100 kilometers and is usually generated by landslides. They are relatively common in exposed areas. The largest known tsunami hit Lituya Bay in Alaska in July 1958 after a rockfall. There, the wave hit a tree at a height of over 500 meters.
  • A regional tsunami forms in a defined area with a radius of about 1000 km. This means that a regional tsunami can cause extensive damage in just one to three hours, leaving little time for evacuation.
  • A teletsunami is an extremely powerful tsunami that can travel more than 1000 kilometers. Tsunamis are quite rare, but do occur a few times every century. The 2004 Indian Ocean tsunami, for example, was a remote tsunami.

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