Science Facts

How Does A Tsunami Occur? – Causes, Effects & Safety


The world’s largest tsunami ever occurred in Alaska 90 million tons of rock and ice fell from the mountains into the bay water shot up 524 meters or 1720 feet into the air. A wave swept across the bay, ripping out trees and throwing one ship, which sat 10 kilometers or 6.2 miles from the epicenter across the island. According to statistics, volcanoes are the cause of about only 5% of such disasters. The rarest cause of tsunamis are asteroids with a diameter of more than one kilometer or 0.62 miles falling into the water.

Tsunamis are usually no higher than a meter or 3.3 feet. The distance between the ridges can reach between 100 to 200 kilometers or 60 to 120 miles in length. That’s at least a thousand times larger than ordinary waves. Their speed is like that of a jet plane. From hurricanes to volcanoes, natural disasters are called natural for a reason as catastrophic.

They’re simply a part of how our planet functions. It does pay to know how and why these things happen. A perfect example of this is the tsunami. These massive walls of water can seem to arrive without warning. A tsunami is essentially a series of enormous waves.

What is Tsunami?

The word tsunami comes from two Japanese words, “tsu,” meaning harbor, and “nami,” meaning waves. It means waves hit the harbor. There are some differences between a tsunami wave and a regular wave. But any wave is an energy carrier. The difference between a tsunami wave and a regular wave is how energy is transferred and how much energy waves pack. A tsunami wave, however, is propagated by some sort of underwater disturbance. These are called “tsunamigenic events.”

A tsunami is a series of fast-moving waves triggered by an underwater shock. It is usually caused by earthquakes or volcanic activity, but landslides or underwater explosions can also drive. Tsunamis were once called tidal waves, but this name isn’t very accurate because tsunamis aren’t related to the Earth’s normal tides. Instead, tsunamis form when water is somehow displaced by force. Most tsunamis reach heights of about 10 feet, but some can be up to 100 feet tall.

If a ship is sitting above the center of this earthquake, it’s safe. The height of the waves beating on its side is about half a meter or 1.64 feet. But in the depths of the ocean, everything is shaking from the bottom to the surface. The deeper the ocean, the higher the crest. And the farther the water recedes, the more glorious the tsunami. The first wave clears the path taking cars, trees, and property with it. The second one carries it all back, destroying buildings and anything in its way.

How does a Tsunami occur?

In deep water, the waves have a small height or amplitude. A wave is an energy. It’s passing through water. And most of the ways that we see are generated by the wind blowing across the surface. Those tsunamis can be caused by a disturbance on the surface, such as a huge landslide or a volcanic eruption.

The most common cause comes from far down below submarine earthquakes that happened deep on the ocean floor. In an earthquake, tectonic plates suddenly shift and change positions along the border between them, called the fault line. When this happens underwater, this dramatic shock immediately sends a jolt. This creates waves that radiate out in all directions along the fault line.

Earthquakes are caused by the movement of the huge tectonic plates that continents sit on. What happens is they come together? In this case, the Pacific plate is moving below the Japanese or Eurasian plate. It causes that plate to end when it sticks there. They’ll be able to much friction. It’ll stick crasher builds up until suddenly it’s released. When they get stuck, the energy of the moving together gets translated to strain energy literally.

Most of their energy is trapped far below the surface. But as the ocean becomes more shallow near land, this energy has to go somewhere. So it gets pushed up, and it takes tons of water with the resulting waves can be miles long, as high as 30 meters or one hundred feet. That’s like a nine-storey building just crashing upon the shore. They can be caused by a disturbance on the other side of the ocean.

Scientific explanation: What is a tsunami caused by? When one tectonic plate suddenly slips beneath the other, the potential energy is released as kinetic energy. This energy is transferred outward from the point of origin. It creates ripples! With a tsunami, these ripples, waves radiate from the point of origin, traveling at hundreds of miles an hour, carrying with them a lot of energy. This intense ocean wave that’s traveling so fast encounters, ultimately, the shoreline. The shoreline that slopes upward compresses the energy of the tsunami wave.

Tsunami Diagram
Tsunami Diagram

It slows its velocity down tremendously, but it also forces it upward. So the tiny wave is now something like a hundred feet, and it’s at the shore. When the first tsunami waves reach the shoreline and slow down, the rear’s waves start to catch up. They compress, forming what’s known as a “tsunami wave train.” Since tsunamis pose such a danger, scientists are constantly trying to figure out how to deal with them.

Scientists who monitor earthquakes are always looking for signs of a possible tsunami. The biggest sign, water suddenly and dramatically receding from the shoreline. This is because as the approaching water is pushed upward into a wall is drawn away from the shore. Of course, knowing that one is coming will not stop. There’s nothing that can stop a tsunami.

The wind, as in the case of ordinary waves, has nothing to do with it. A short, powerful impulse pushes the mass of water from underwater. A large-scale sharp shift in the ocean occurs. The cause may be an earthquake, volcanic eruption, landslide explosion, the collapse of rocks, glaciers, or asteroids impacting the water. But the main culprit in 88 cases is seismic.

The driving energy of a tsunami, unlike an ordinary wave, passes through the water, not on top of it. So 95 of the life cycle of a tsunami is invisible to the eye. The lithospheric plates of the earth’s crust shift. The shake is powerful, almost eight points which means that a tsunami can’t be avoided. Because of the shocking, part of the seafloor rises while another drop. The ocean begins oscillating vertically, launching a series of waves.

What are the effects of Tsunami?

Tsunamis are some of the most devastating natural disasters. For most people who live inland, the greatest threat is from overflowing the rivers and creeks. Excess water causes deadly currents, which drag people away and drown them. Tsunamis also caused huge property and infrastructure damage costing millions to repair. The cost to human life can be devastating as well. The deadliest tsunami in recorded history was the infamous 2004 Boxing Day tsunami. The death toll here was estimated at over 300,000 people.

Tsunami has a rare scientific effect. It speeds up the rotation of the earth. The immediate destruction is only the beginning of the damage. After the waters recede, there is often an elevated risk of disease created by stagnant and contaminated water. Since most tsunamis occur south of the Equator, this only raises the risk of disease further.

A tsunami struck Japan on March 11th, 2011. This was caused by an earthquake measuring nine on the Richter scale. The largest earthquake ever hit Japan in recorded history. The Japanese national police agency officially confirmed that over 14,000 people were killed, over 4,500 people were injured, and 14 thousand nine hundred people were declared missing. Over 125,000 buildings were damaged or destroyed. There were 4.4 million households that had their electricity supply cut off, including 11 nuclear power plants. This accident was the second biggest nuclear catastrophe ever after the notorious Chernobyl disaster.

How to be prepared for a Tsunami?

A tsunami can strike any coast, any time. It’s one of the most destructive forces in nature. Even small tsunamis can be dangerous, especially to swimmers, surfers, and boats in harbors. But there are ways you can prepare. Now you’ll learn how to prepare for a tsunami and what to do if one occurs.

First, understand the warnings. If an official warning is issued, do what it says. Pay attention to warnings Mother Nature provides. Stay out of the tsunami hazard zone until officials tell you it’s safe.

  • Go rapidly inland to higher ground.
  • Stay away from rivers that flow into the ocean and from the beach or the coast.
  • Wait until at least one hour has passed.
  • Do not touch fallen power lines.
  • Follow safety advice broadcast on the radio by authorities.
  • Do not go to school to pick up your children. Teachers are trained to deal with disaster situations.
  • If you have to leave your home, unplug all household appliances and turn off the water and electricity at the mains.
  • Take any important documents with you, have your disaster kit and first-aid kit.

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