Earthquake are taking place very frequently all over the world. The shaking of the earth as a result of these quakes is called a "Tremor". Most of these tremors are weak and do not cause any damage, however there are others which are so powerful that they cause crevices to appear in the land and buildings to collapse.
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In India one of the most recent earthquakes was the one which cause devastation in many areas of the state of Gujarat. The vibrations of an earthquake are picked up by sensitive equipment and the science of studying these shock waves is called 'Seismology'. The intensity of an earthquake is measured on a scale of 1 to 12, this scale is called the "Richter" (pronounced as Rikter) scale. Earthquakes which measure 1 or 2 on the Richter scale may not be felt by people while the ones which measure between 7 and 12 may cause damage. The place inside the earth, where an earthquake occurs, is called the 'Focus' while the place on the Earth surface where it is strongest is called the 'Epicentre'.
Most earthquakes occur only in certain areas of the Earth. These areas are called the earthquake belts. These earthquake belts are generally located close to the edges of the various plates of the Earth's crust. The shifting of the plates also leads to volcanic eruptions, where new plates are being formed, the leva generally flows out gently, in the form of basalt, and these volcanoes are called basaltic volcanoes. In other places the Earth's crust is slowly being destroyed and volcanic eruptions in these places are more dangerous, these volcanoes throw out molten crust in the form of 'Andesite' and these volcanoes are called Andesite volcanoes. Both these types are in belts along the plates on the Earth's crust, as shown in the illustration. It is difficult to predict an earthquake in advance but in some cases scientists have been successful in making these predictions thus saving human lives.
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