Tsunamis are gigantic waves which can be 30 metres high and 200 kilometres long. The word tsunami means ‘harbour wave’ in Japanese because of the way the waves crash into the harbour. They are also called tidal waves.
Is it true?
The biggest tsunami was as tall as the Statue of Liberty.
YES. This colossal wave was 85 metres high, almost as tall as the Statue of Liberty. It swept past Japan in 1971.
A tsunami can travel across the sea at high speed. Some race along at 900 kph. That’s as fast as a jet plane. The deeper the water, the faster they flow.
How do tsunamis start?
Tsunamis are triggered off by volcanoes or earthquakes under the sea. At first, the waves are low as they speed across the sea. As they reach land, the water piles up into a massive wave which crashes down on to the shore.
What happens when a tsunami hits law
When a tsunami hits land, watch out! It smashes on to the shore, washing houses, people and boats away, i can sweep a boat into the air and dump it far away.
How do floods happen?
Many floods happen when it rains very heavily and rivers overflow. They burst their banks and flood the land all around. You also get floods in stormy weather when high tides or gigantic waves sweep on to the shore.
The Thames Barrier was finished in 1984 to stop the River Thames flooding and drowning London. Ten huge steel gates swing up to make a massive dam.
What are flash floods ?
Flash floods are floods which happen very suddenly, with no warning. Sometimes there isn’t time to evacuate buildings in the flood’s path. Flash floods can happen in the desert too, during a rare downpour of rain.
Are some floods useful?
Yes, they are. The River Nile in Egypt used to flood every year, leaving rich mud on the fields. The mud made the soil ideal for farmers to grow bumper crops. The Nile doesn’t flood anymore because a large dam was built to store its water.
It Is it true?
Floods can wash whole buildings away.
YES. In 1955, a flood in the USA washed a four-storey wooden hotel clean away. Imagine how surprised the guests were when they looked out of their windows!