- Tsunamis are large waves caused by the displacement of large volumes of water.
- They can be triggered by underwater earthquakes.
- Volcanic eruptions and landslides that slide into the sea can also cause tsunamis.
- A tsunami will usually be more powerful the closer to land it starts, this is because it loses energy as it travels towards land.
Characteristics
- In deep open water the waves travel at a very high speed of 500-900 km/h, with a long wavelength and a small amplitude of about 1m.
- Closer to land in shallower water the waves energy becomes more compressed and therefore more concentrated. So the waves slow down, their wavelength decreases, but their amplitude increases to many metres.
- Just before the wave reaches the coast, the water withdraws down the shore.
- Tsunamis warning systems rely on earthquake detection systems.
- Tsunami warning centres are located all around the world (Alaska and Hawaii).
- If people don't have good communication systems they will not receive the warning in enough time to evacuate, especially if the earthquake has happened close to land, then it wont take the tsunami long to reach land.
- Buildings designed with raised, open foundations and made of a strong material such as concrete are less likely to be damaged by the force of water.
- In some places, such as Hokkaido, Japan, tsunami walls have been built around settlements to protect them. However waves can be taller than these sea walls.
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