ICSE BoardEnglish MediumSTD 9GeographyVolcanoes3 Marks
Question
Describe the causes of volcanic eruptions.
✓
Answer
The main causes of volcanic eruptions are the following :
Heat and Pressure inside the Earth: Temperature and pressure both increase from the surface towards the centre of the earth. Rocks are bad conductors of heat. So the earth’s heat does not escape on its own. Instead, it melts the rocks and builds up great pressure. The pressure forces the heat to find an escape route through fissures and cracks in the rocks.
Plate Tectonics: Most volcanic eruptions take place near plate margins. The same forces that cause earthquakes also cause volcanic eruptions.
Magma Chamber: The molten material while still under the earth’s crust melts weak rocks and creates a huge chamber for itself. Fresh magma continues to pour inside the chamber. Since magma contains silicate materials gases and water vapours the pressure always acts vertically upwards. Once a route is found it rises to the surface
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