A volcano is an opening or rupture in the earth’s crust through which lava, volcanic ash, and gases escape out of the earth’s crust. Beneath a volcano, liquid magma containing dissolved gases rises through cracks in the Earth’s crust. As the magma rises, pressure decreases, allowing the gases to form bubbles.
Volcanic activities have a profound influence on the Earth’s landforms. Solid liquid or gaseous material may find their way to the surface from some deep-seated Reservoir beneath. Molten magma is mobile rock that forces its way into the plains of weakness of the crust to escape quietly or exclusively to the surface.
The ancient greeks believed that volcanic eruptions occurred when vulcan the God of The Underworld stroked his subterranean furnace beneath the volcano, an island in Sicily from where the present word volcano is derived.
Geologist and volcanologist have confirmed that volcanic activity is closely connected with the Crustal disturbances particularly where there are zones of weakness due to the deep faulting or mountain folding.
As the depth of the earth increases the temperature also increases. The interior of the earth is in semi molten state comprising of solid liquid and gases materials which are very hot and are collectively called magma.
The Magma is very hot and heavily charged with the gases such as carbon dioxide, nitrogen etc. The gas and vapour increases the mobility and explosiveness of the magna which cause the volcanic eruption. These materials are then admitted to the vent of a volcano during the eruption.
Volcanoes are located in a clearly defined pattern around the World and are closely related to the regions that have been intensively folded or faulted. Therefore folding or faulting of region is one of the main reasons that cause the eruption of volcano.
Examples of active volcano which erupted in the recent years are Mount pelee, Mount Krakatau etc.
Different types of volcanoes have different types of lavas. Some have acid lavas while others have basic lavas. This composition of lava determines the amount of damage the volcanic eruption will produce.
Acid lavas are highly viscous and cause less damage whereas basic lavas are the hottest and highly fluid and cause widespread damage to life and property.