Process of Volcanism

Volcanism can be defined as the eruption and extrusion of internal molten rocks of Mantle onto the surface of the earth. The volcano erupts through a crater of the volcano. The eruption of lava and gases takes place as a result of the fast movement of lava/ magma. Scientists use the term magma for the molten rocks, which are still underground and not erupted out, while the term “lava” is used against the erupted molten rocks through the vent of the volcano. Through the process of a volcano, a huge quantity of molten magma pours onto the surface of Earth. In addition hot springs (geysers) also come into existence. Thus volcanic activity brings enormous change and causes huge destruction of life in the neighborhood. There are a number of examples of catastrophic events caused by a volcanic eruption in history. For instance, the great volcano “Vesuvius” erupted on August 24, AD 79, which buried the city of Pompeii under a 20 feet thick layer of volcanic debris and ash. This volcano was 400 feet high of the bay of Naples. The Vesuvius volcano again erupted in 1631, which put 4000 people into the trench of death, and destroyed 15 villages completely. Similarly, the volcanic activity of Mt. Karakatoa (between Samatra and Java) in 1883, extruded huge amount of magma. The explosion caused 100 feet high tidal waves in the sea, which killed 3600 people in the nearby coastal towns. In May 1902, the eruption of Mt. Pelee (West Indies) ejected gigantic white-hot lava, and super-heated steam, which killed 30,000 people along with the complete destruction of the city of Martinique.

Vulcanicity: The term “Volcanicity” is broader than “Volcanism”. It includes all the process of convection and movement of the magma, and extremely hot gases within the mantle, the pressure created due to this movement, and the ejection of these materials in the form of lava onto the surface of earth. Vulcanicity comprised of two forms.

(1). Intrusive Vulcanicity:

(2). Extrusive Vulcanicity:

(1). Intrusive Vulcanicity:

As the name implies the Intrusive vulcanicity occurs when the magma enters and solidifies in lines of weakness or chambers in the earth’s crust. Intrusive Vulcanicity has many forms, such as dykes, sills, batholiths, and laccoliths. Out of these “Dyke” is a form in which magma has cut vertically across pre-existing strata forming a kind of barrier wall. On the other hand, ”Sill” is a form of vulcanicity in which magma has inserted itself as a thin layer between strata of pre-existing rocks without disturbing those layers. While in the “Lacolith Form” the magma pipe becomes dome-like pushing up the upper strata of rocks into a bulge. A batholith is another form of intrusive Vulcanicity, in which a massive body of intrusive molten igneous rocks, which destroys most of the geologic structure located around.

(2). Extrusive Vulcanicity:

When the molten magma extrudes out on to the surface of the Earth, it is known as the Extrusive Vulcanicity. Extrusive Vulcanicity depends on the nature of the material ejected out in the form of lava. In other words, the composition of lava determined the type of vulcanicity. The extrusive material of the volcano consists of Lava (the liquid product), Tepra (Solid and gaseous material). Tepra is ejected in the form of compounds of sulfur, and hydrogen with carbon dioxide.