A volcano is an opening in the earth’s crust through which gases, molten rocks materials (lava), ash, steam etc. are emitted outward in the course of an eruption. Such vents or openings occur in those parts of the earth’s crust where the rock strata are relatively weak. Volcanic activity is an example of endogenic process. Depending upon the explosive nature of the volcano, different land forms can be formed such as a plateau (if the volcano is not explosive) or a mountain (if the volcano is explosive in nature).
Magma vs Lava: The difference:
- ➢ Magma is the term used to denote the molten rocks and related materials seen inside earth. A weaker zone of the mantle called asthenosphere, usually is the source of magma.
- ➢ Once this magma came out to the earth surface through the vent of a volcano, it is called as the Lava. Therefore, Lava is nothing but the magma on earth surface.
- ➢ The process by which solid, liquid and gaseous material escape from the earth’s interior to the surface of the earth is called as Volcanism.
Types of Volcanoes:
- ➢ Volcanoes are classified on the basis of nature of eruption and the form developed at the surface.
➢ Shield Volcanoes
- ➢ How to identify: They are not very steep but are far and wider. They extend to great height as well as distance.
- ➢ They are the largest of all volcanoes in the world as the lava flows to a far distance.
- ➢ The Hawaiian volcanoes are the most famous examples.
- ➢ Shield volcanoes have low slopes and consist almost entirely of frozen lavas.
- ➢ If you were to fly over top of a shield volcano, it would resemble a warrior’s shield, hence the name.
- ➢ These volcanoes are mostly made up of basalt (less viscous), a type of lava that is very fluid when erupted. For this reason, these volcanoes are not steep.
- ➢ They are of low explosive in general, but if somehow water gets into the vent, they may turn explosive.
- ➢ The upcoming lava moves in the form of a fountain and throws out the cone at the top of the vent and develops into cinder cone.
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