Volcanoes : Formation, Types & Distribution

Volcanoes

Volcanoes means the place or mouth through which the flame is emitted, that is, the place of the earth's crust, the hole or the hole from which lava, ash, gas Water vapor (erupt) occurs at a rapid or slow pace. are called volcanoes. In this process, activities are included from the exit of magma, lava or other substances from the interior of the earth to their cooling. The main reason for this is the pressure exerted on the crust by magma and hot gases.

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Type of Volcano

Different types of substances have come out in volcanic action. These include everything from fine dust particles to large pieces of stone. Lava is main in its eruption, which is of acidic or alkaline type. Apart from this, different types of gases also come out from its excrement. 

Volcano can be divided into different classes on the basis of its eruption, time period and fluidity etc., which are as follows –

1. Depending on the fluidity of the lava
   1. Acidic
   2. Alkaline
2. On the basis of chemical and mineral composition present in the lava
   1. Felsic group
   2. Mafik group
   3. Ultramafic group
3. Depending on the intensity of the Lava Eruption
   1. Central erupting volcano
      1. Pelean type
      2. Vulcanian type
      3. Stromboli type
      4. Hawaiian type
   2. Crack erupting volcano
4. On the basis of Activity
   1. Active volcano 
   2. Dormant volcano
   3. Dead or Extinct Volcano

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1. Depending On The Fluidity of The Lava 

The lava that comes out in a volcanic eruption is either thick or thin. Thick lava is acidic and thin lava is alkaline. Their presence affects the intensity of the eruption in the eruption. Mountains and plateaus are formed by them. Depending on the fluidity of lava, it is of two types, acidic and alkaline.

a. Acidic

Acidic lava is very thick. Its melting point is high due to which it freezes quickly. The amount of silica in it is high, due to which there are explosive eruptions in the volcano. Due to its rapid solidification, mountains and cones with steep slopes are formed. In this, the proportion of metallic minerals is less. Like – Vesuvius, Vulcanian.

b. Alkaline

Alkaline lava is more fluid. Its melting point is low, which means it freezes late. Due to late freezing, it spreads far and wide, due to which plateaus and shields are formed. The proportion of metallic minerals is high in this. Like – shield volcano located in the Hawaiian Islands.

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2. On the Basis of Chemical And Mineral Composition Present in The Lava 

There are many types of minerals in the lava that comes out of the volcano. These minerals are light or dark in color. On the basis of minerals present in it, it is divided into three groups – felmensic group, mafic group, ultramafic group.

a . Felsic group 

Light colored minerals are called felsic. Silica dominant minerals have been kept in this group. Like – quartz and feldspar.

b. Mafik group 

Dark colored minerals are called mafic. Minerals having excess of magnesium and iron elements have been kept in this group. Eg – Pyranxim, Amphiboles, Allwein

c. Ultramafic group

Minerals with properties intermediate between felsic and mafic are called ultramafic. The minerals of this group have high amounts of silicon and aluminium.

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3. Depending On The Intensity of The Lava Eruption 

How does lava come out of a volcano? It comes out from the central mouth or through the cleavage of the cone. 

On this basis, it can be divided into two types, which are as follows –

a. Central erupting volcano 

When lava erupts from a vent, it assumes a domed or conical shape. Most of the world's volcanoes belong to this category. Depending on the intensity of lava coming out of the central vent (in decreasing order), the volcanic cones are divided into Pelean type, Vulcanian type, Stromboli type, Hawaiian type. | Of all these, the equivalent of Pelion is the most destructive.

i. Pelean type 

The lava coming out of it contains silica content, due to which it is highly acidic and viscous. It is most destructive. Due to the presence of silica, the explosion in it is fierce. In this, each subsequent eruption comes out breaking the volcanic cones formed by the previous eruption. Like – Mount Pili located on Martinique Island of Western Islands, Krakatoa near Sumatra and Java Island.

ii. Vulcanian type

It was named after the Vulcans located on Lipari Island. The matter coming out of it comes out with fierce explosion and more intensity. Every type of magma from acidic to alkaline emerges from it. At its exit, dust and ash-laden gases rise to great heights in the form of huge dark clouds, which look like a cauliflower.

iii. Stromboli type

The amount of acid in the lava coming out of it is less, due to which it is somewhat thin. There is usually no explosive eruption in this and the gases keep coming out intermittently or continuously. Like – Volcano located on Lipari Island.

iv. Hawaiian type

Its eruption is very calm and there are no explosive activities in it. The lava that comes out of it is very thin and alkaline, due to which it spreads far and wide. In this, the cones are of lesser height and spread over longer distances. This type of volcano is found more on the island of Hawaii, due to which it is called Hawaiian equivalent volcano.

B. Crack Erupting Volcano

When the intensity of lava and gas in the volcano is less or their quantity is less, then the mouth of the volcanic cone is not able to open. Due to this lava and gas start coming out through the cracks. The lava that comes out of it is thin and alkaline, which flows far away. Thus it forms a plateau. At present, this type of volcano is rarely seen, but in the past many plateaus were formed by it. Like – Deccan Plateau of India, Plateau of Colombia.

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4. On the basis of Activity

On the basis of continuous or periodic eruptions from the volcano or on the basis of its activity, it is mainly divided into three parts, which are as follows –

a. Active volcano

Such volcanoes from which lava, gas and disintegrated material always keep coming out. are called active volcanoes. Like – Italy's Etna, Ecuador's Cotapaxy (world's highest active volcano), Lipari Island's Stromboli (Mediterranean Sea Lighthouse), Mona Lova of Hawaii Island, Mount Arkash of Antarctica.

b. Dormant volcano

Such volcanoes which are quiet for years, but can erupt anytime, are called dormant volcanoes, such as Fujiyama of Japan, Krakatoa of Indonesia, Vesuvius of Italy etc.

c. Dead or Extinct Volcano

Such volcanoes, from which there has been no eruption for thousands of years, nor is there any possibility of it in the future. Dead or dormant volcanoes are called. Like – Kenya and Kilimanjaro located in the eastern part of Africa, Chimbarajon of Ecuador, Popa of Myanmar, Demband of Iran and Ekakangua located in Kohsultan Andes ranges.

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Distribution of Volcanoes

Most of the volcanoes are found on the edges of destructive plates, about 80% on the edges of destructive plates, 15% on the edges of constructive plates and the remaining 5% in the inner parts of the plates. Their details are as follows –

1. Peri-Pacific Ocean Plate 

2/3 of the world's volcanoes are found on both the coastal parts of the Pacific Ocean. It is called the fire ring or chain of fire of the Pacific Ocean. Ecuador's Catopaxi (highest active volcano), Chile's Aconcagua (highest active volcano)

2. Central Continental Belt

Most of the volcanoes of this belt meet with the help of the edges of the destructive plate, because here Eurasian plate, African plate and Indian plate meet. This belt extends from near the Canary Islands to Indonesia, where it meets the Peri-Pacific Ocean belt. Strombeli, Vesuvius, Devmand, Koh Sultan, and Krakatoa come under this.

3. Mid-Atlantic Ridge or Mid-Oceanic Ridge

Where – where the fault is formed due to the divergence of two plates, it is found there. Ridge is formed by this. Eg – St. Helena, Iceland, Azores Island

4. Inter Plate Volcano

In this the volcano is located inside the oceanic or continental plate. The reason for its origin is considered to be a hot place. By this a linear series is formed. In this, new volcanoes are located at one end and old volcanoes at the other end. such as the Hawaiian Islands

5. Other Regions

Madagascar, Mauritius, Indian Ocean etc.

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Distribution of Volcanoes in India

At present there are no active volcanoes on the mainland of India, but in the past there were many such areas. Many topographies were created in India by them. Their brief details are as follows –

1. Dalma region – Near Jamshedpur, this is the oldest volcanic region of India.
2. Cuddapah, Bijawar, Gwalior region – In all these three regions there was a boom in the Cuddapah period.
3. Malani, Kirana area – In these areas there was an eruption in the Vindhya period. The Malani range is situated near Jodhpur and at the northern end of the Kirana hill Aravalli.
4. Lower Himalayan region – In these regions there was eruption in Paleojivakalpa. In this comes the Pir Panjal range, the upper valley of Sutlej, Garhwal, Nainital etc.
5. Rajmahal and Abor hill area – In this area, there was an eruption in the Jurassic period. It extends from Bihar to Assam.
6. Deccan region of India – In this region there was an eruption in the Cretaceous period.

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