VOLCANO IS BOTH A CURSE AND A BOON.

VOLCANO is a fissure or vent or an opening formed in the earth’s

crust through which hot and molten material or magma in the form of lava, steam and gases come out from the interior of the earth to the surface with a great force. 

This activity of the earth occurs as an explosion through the vent which becomes larger in size and is called the crater. the development of magma and gases in theinterior of the earth and their tendency to create pressure vertically upward cause a volcano. The materials coming out in violent explosion spread around the crater and solidify and take the shape of a  volcanic mountain.

 In a volcanic eruption gases like carbon dioxide, Sulphur dioxide,

nitrogen dioxide, hydrogen and carbon monoxide and metallic

materials & minerals comes out to the surface. The molten rock , i.e., lava may be associated with the fluidity or viscosity. The fluid lava spreads out on the ground up to a maximum speed of 100km per hour.

Viscous lava spreads slowly but it is as hot as between 1000 degree

centigrade and 1200 degree centigrade

 Volcanoes may be of three types- Active, Dormant and Extinct. An

active volcano is one which constantly ejects lava, gases, ashes and

other materials. Etna and Stromboli of the Mediterranean Sea are

significant examples of active volcanoes.

Etna (in Italy) has been active for the last 2,500 years. There are such about 500 active volcanoes in the world. Dormant volcano is one which does become inactive after an eruption for some time but may erupt violently at any time in future. Extinct volcano is one which does not indicate for future eruption and the crater of such volcano is filled up with water and forms lake in the crater.

Volcanoes are highly destructive on one hand and on the other; they

are highly useful to human activities. Volcanoes may destroy standing crops and force people to vacate large area of human habitation. However, they prove to be useful as volcanic eruption form objects of scenic beauty in water springs of mineral water and geysers. Plateaus on the earth are formed from the deposition of volcanic materials.

Volcanic Mountain is sauce of minerals and volcanic rocks. When

weathered and decomposed they become very fertile for vegetation.

Dust and ashes deposited in a volcanic activity are used as highly fertile soils. Hence, volcanoes are both curse and the boon.

RANDHIR KUMAR

CLASS - XII SCIENCE

ROLL NO. - 27

SESSION - 2011-12