The word Tsunami or ‘harbour-wave’ comes from the Japanese word ‘tsu’, which means harbour and ‘nami’ which means wave. They are commonly known as ‘killer waves’. Sounds a bit scary doesn’t it? Well you definitely wouldn’t want to be around when a tsunami happens.
A Tsunami is usually a huge amount of ocean waves which get stronger as they move along. It’s caused by pressure in the atmosphere, a volcanic explosion, an underwater earthquake or landslide or even a meteor hitting the ocean.
Volcanic explosions happen when the plates of the Earth’s crust move and crash together, which causes a build-up of pressure from the magma, which is molten rocks and gas, squeezing up between them and then rising to the surface. It eventually explodes.
Earthquakes happen when there is a huge amount of stress released from huge rocks on the Earth’s crust cracking and slipping past each other. This causes the earth to shake.
They seem to have been around for some time and go back as far as 6225-6170 BC in the North Atlantic Ocean. There was another one in Greece in 1600 BC which caused a lot of damage to the civilization on Crete at the time.
They have happened all over the world including Greece, Italy, Israel, Venezuela, Great Britain, Canada, Portugal, Taiwan, Indonesia, Chile, Newfoundland, USSR, Alaska, New Zealand and by far the most occurrences have been in Japan, that’s why the name comes from the Japanese language. Wow, that’s a lot of places that have had tsunamis.
Tsunamis are not like normal tidal waves and the water from them flows straight and with unbelievable power. Typical waves are where the water flows in circles. This might amaze you…they can travel at speeds of up to 500 miles (805 kilometres) per hour without losing energy as they go along.
The Tsunami that hit Hawaii in 1946 was going almost as fast as a jet plane. That’s seriously fast. Because of this, their arrival can often be calculated. How big do you think a normal wave gets at a beach? Well it is normally about 3 foot (1 meter) high. Now a tsunami wave can reach a height of 100 feet (30.48 meters) high, that’s amazing. But the highest recorded one was the 1958 Lituya Bay, Alaska Megatsunami with a recorded height of 1,719 feet (524 meters). Whoa, that’s one seriously tall wave.
The Asian Tsunami in 2004 in the Indian Ocean is considered the deadliest Tsunami ever, which was caused by an earthquake with the energy of 23,000 atomic bombs! This brought with it incredibly destructive waves hitting the coastlines of eleven countries from Thailand to Africa, killing 283,000 people and wiping out cities.
The power of the water picks up aeroplanes, ships, houses and anything in its path and tosses them around like corks. Even after a Tsunami has finished, the mainland is often destroyed by a lot of salt deposits on the land so people die from hunger and disease.
Signs of a Tsunami are earth quakes, rumbling in the ground, when the sea pulls back leaving bare sand or when animals behave strangely or start leaving. That’s the time to move away from the beach and run to higher ground, not stopping to get possessions.
People survive by not trying to swim, as the current pulls you in the opposite direction. They rather try and find a floating object and hold on going where it goes with the moving current, this could be a tree trunk or piece of a building. Palm trees planted on the shore have saved people as they can survive the force of impact of the waves but often trees snap under the force of the water so climbing a tree isn’t always the best idea.
Indigenous people like the semi-nomadic Onge and the Jarawa of the South and Middle Andaman Islands generally survive Tsunamis far better than westernised populations as the wisdom of survival has been passed down through their generations.
Tsunamis can be really dangerous, but it’s an interesting geography lesson too! Do you know any other facts about Tsunamis?
Next, test your knowledge of Tsunamis by taking our Tsunami quiz – all answers can be found on this page.