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Tsunami
A tsunami is a series of ocean waves that are usually caused by seismic events. Watch the footage of the 2004 Indian Ocean tsunami.
The word tsunami is a Japanese word and is pronounced ‘soo-nah-mee’. It means ‘harbour wave’ with ‘tsu’ meaning harbour and ‘nami’ meaning wave.
Japan has experienced many tsunamis throughout its history. Along Japan's coastline, there are many bays which act like funnels and concentrate the energy in tsunami waves. While the tsunami is barely noticed by those who are fishing at sea, it is certainly noticed by those in the settlements in the bays and harbours.
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Tsunami written in
Japanese text
Sometimes tsunami are called ‘tidal waves’, but this is not correct. Tsunami are not caused by the tides. Although tsunami impact on a coastline can be affected by tide level, tsunami are unrelated to tides. Tides are affected by the gravitational pull of the sun and moon, while tsunami are usually caused by earthquakes.
Tsunami are usually formed by undersea events that create sudden and large disturbances to the water in the ocean.
These underwater events can be caused by:
- earthquakes
- landslides
- erupting volcanoes
- other movements in the Earth’s crust, and
- large explosions.
A tsunami could also be caused by events above the ocean floor, such as:
- a meteorite crashing into the ocean, and
- major landslides.