Notes On Volcanoes, Tsunamis and Cyclones - CBSE Class 10 Geography
The earth is filled with molten magma at very high temperature. This molten magma is under enormous pressure and is on the constant lookout for an opening. When it finds one, all the molten rocks or lava, along with gases and steam flow out on to the earth’s surface. This is called a volcano. When extraordinary levels of pressure develop within the earth, the lava and gases explode causing great destruction to the surrounding areas. Such violent eruptions are also accompanied by earthquakes. Depending on their activity, there are three types of volcanoes: active, dormant and extinct. The active volcanoes erupt from time to time. The dormant ones were active in the past, though they have not shown any activities for a long time. The extinct ones on the other hand, do not have any recorded history of being active. Earthquakes and volcanic eruptions cause a sudden disturbance at the base of the ocean, causing abrupt displacement of water. Such activities produce very high waves which are called Tsunamis, also known as killer waves or tidal waves. A cyclone is an egg-shaped air formation that moves in the form of swirling winds. It has low air pressure at its centre but very high pressure at the surface. Since air moves from a region of high pressure to a region of low pressure, cyclones cause high winds and heavy rainfall. Since satellites help us in tracking the course of cyclones, the Indian Meteorological Department issues cyclone warnings in India.

#### Summary

The earth is filled with molten magma at very high temperature. This molten magma is under enormous pressure and is on the constant lookout for an opening. When it finds one, all the molten rocks or lava, along with gases and steam flow out on to the earth’s surface. This is called a volcano. When extraordinary levels of pressure develop within the earth, the lava and gases explode causing great destruction to the surrounding areas. Such violent eruptions are also accompanied by earthquakes. Depending on their activity, there are three types of volcanoes: active, dormant and extinct. The active volcanoes erupt from time to time. The dormant ones were active in the past, though they have not shown any activities for a long time. The extinct ones on the other hand, do not have any recorded history of being active. Earthquakes and volcanic eruptions cause a sudden disturbance at the base of the ocean, causing abrupt displacement of water. Such activities produce very high waves which are called Tsunamis, also known as killer waves or tidal waves. A cyclone is an egg-shaped air formation that moves in the form of swirling winds. It has low air pressure at its centre but very high pressure at the surface. Since air moves from a region of high pressure to a region of low pressure, cyclones cause high winds and heavy rainfall. Since satellites help us in tracking the course of cyclones, the Indian Meteorological Department issues cyclone warnings in India.

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