This third KS3 Geography quiz takes a final look at earthquakes and volcanoes. Volcanoes come in many different shapes and sizes. Some of them are steep-sided and conical. Others have a flatter and wider profile. It all depends on the type of lava that they erupt. Volcanoes that erupt runny lavas form the flatter and wider type. These are called shield volcanoes.
Good examples of shield volcanoes are the ones that make up the Hawaiian Islands in the Pacific Ocean. Volcanoes with very thick lava form the type with the steeper sides. These also tend to have explosive eruptions that send pyroclastic flows racing down from the top. These are very destructive. A good example of this type is Mount St. Helens in the USA.
[readmore]Most volcanoes occur at the edges of the tectonic plates (places known as plate boundaries). There are three types of plate boundary - constructive, conservative and destructive. As well as volcanoes, you get earthquakes at plate boundaries. As the plates move, the rocks get stuck together but the plates continue to move. When the pressure builds up to a certain level, the rocks that are stuck will break and that part of the plate will suddenly move a distance of several metres. This releases a lot of energy and the point at which it happens is called the focus of the earthquake.
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You can find more about this topic by visiting BBC Bitesize - Disasters and responses
They are huge tidal waves - tsunami means 'harbour wave' in Japanese
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It was a huge eruption - the mountain literally blew its top. After the eruption had stopped, the mountain was 400 m lower and had a crater at the top that was 2 - 3 km wide and about 700 m deep
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Movement of plates causes 'quakes and eruptions
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Also known as a plate margin
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Mauna Loa in Hawaii is an excellent example
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The closest active volcanoes to the UK are in Italy and in Iceland
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You don't usually get volcanoes at conservative plate boundaries
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Seismic is Greek for 'shake'
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A cloud of hot ash from an eruption of Mount Vesuvius in AD79 destroyed the town of Pompeii. The ash was so fine that the bodies of the victims were very well preserved
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The seismic waves travel outwards from the focus in all directions. That is why it is possible to detect an earthquake that has happened on the other side of the world
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