Earthquakes and Volcanoes 03
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.
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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