What is a volcano and how does it erupt? , type of volcano

In today’s article, you will know about what is a volcano and how it erupts . As we know, the Earth’s mantle is very hot, where the temperature ranges between 1000 ° C to 3000 ° C. In such a situation, the rocks present inside melt due to high temperature and form a liquid. This molten fluid is called magma which is lighter than rocks. Due to being lighter, it reaches the upper surface of the earth and starts coming out, due to which the volcano is born.

Today in this article, we will study in detail about volcanoes, where what is a volcano , how and where a volcano erupts , types of volcanoes,   etc. will be given. So let’s start and know the complete information about the volcano 


What is a Volcano? – What is Volcano full information.

A volcano, which is called a ‘volcano’ in the English language, is a crack or hole made on the surface of the earth from which lava, hot pieces of rock, ash and hot gases come out. 

The name Volcano originated from the name of the Roman fire god Vulcan. When the substances emanating from a volcano accumulate and take the form of a conical site, it is called a volcanic mountain.

Volcanoes form many landforms, so in geomorphology it is seen as a sudden event and is classified as a constructive force that changes the Earth’s surface. .

At the same time, environmental geography sees it as a natural disaster, because it causes loss of ecosystem and life and property.

difference between lava and magma

Although lava and magma refer to the same compound, they differ from each other on the basis of location and behavior. Magma is a hot liquid formed by the melting of rocks present within the earth and when this fluid comes out of the volcano with a mixture of gases, it is called lava .

How does a volcano erupt?

Volcanoes erupt when molten rocks beneath the Earth, called magma, rise to the surface. Magma is formed by the melting of rocks in the Earth’s mantle.

Our Earth’s surface is broken up into a series of plates, which are called tectonic plates. When these tectonic plates move away from each other or slide under each other, the process of melting of the Earth’s mantle begins and magma is formed.

Magma is lighter than rocks, so it rises towards the surface of the earth. As magma rises to the surface, bubbles of gas are formed in it. The magma coming upwards starts coming out from the cracks or holes formed at the boundaries of tectonic plates on the surface of the earth, which is called lava.

If the magma is thick, then the gas bubbles cannot escape easily and the pressure increases as the magma rises. When the pressure gets too high, a loud explosion occurs. This explosion can be dangerous and destructive.

Another reason for the explosion – When water below the surface comes into contact with hot magma , it forms steam, this steam can build up enough pressure to cause an explosion.

Why does a volcano erupt?

Before knowing the reason for the eruption of volcano, we have to understand the structure of the earth. The topmost surface of the Earth is the lithosphere, which includes the crust and mantle. The thickness of the crust can range from 10 km to 100 km in mountainous areas.

Earth’s crust is classified into different parts including mantle. The upper cover included in it lies between 8-35 km to 410 km . After this comes the transition zone which is from 410 to 660 km and finally comes the lower cover which is located between 660 km to 2891 km .

Magma is formed in the depths of the Earth’s crust and in the upper part of the mantle. In these regions the temperature (between 700° to 1,300° C) and pressure are very high and it is these changes in temperature and pressure that form magma. 

The upper part of the Earth’s mantle is made up of very hot and solid rock. This rock is so hot that it can flow like a soft chewing gum, even if it is solid. If a rock with this temperature were on Earth, it would be in a molten state. But this rock does not melt in the mantle because there is high pressure due to the rocks above it.

formation of magma

In the Earth’s mantle (where magma is formed) the temperature is always the same. Magma usually forms when there is a decrease in pressure. Therefore a lot of magma is formed between the boundaries of the separating tectonic plates, where the pressure is reduced. Magma, where it forms, is less dense than solid rock . Therefore it rises towards the surface due to which the volcano erupts.

Where does a volcano erupt?

Where does a volcano erupt?
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Our Earth is divided into 17 solid tectonic plates. Most volcanoes are found at the boundaries of tectonic plates. For example, there are many volcanoes on the boundaries of plates around the Pacific Ocean. Hence, this area is also called “Ring of Fire” .

Remember tectonic plate boundaries are areas where plates move away from each other or collide or slide under each other. Most volcanoes are found where plates move away or come closer. About 15% of active volcanoes exist where the plates separate, and 80% of active volcanoes are where the plates collide. The rest of the volcanoes are far beyond the boundaries of these plates that originate at hot spots.

Magma formation when tectonic plates break away

When tectonic plates separate, a divergent boundary is formed. A deep rift is formed between these plates which is called ‘Rift Zone’ . The casing rock rises upwards to fill this space. When the mantle rock approaches the surface, the pressure decreases. Due to the decrease of this pressure, the rock melts and magma is formed. Magma moves towards the rift zone and comes out.

Most of the divergence boundaries are at sea level. Volcanoes and mountain ranges are formed when lava emerges from the rift zone under the ocean. These volcanoes and mountain ranges are called ‘mid-oceanic ridges’ .

Magma is formed when tectonic plates collide

When tectonic plates collide, a convergent boundary is formed. When an oceanic plate collides with a continental plate, the oceanic plate slides under the continental plate. This process is called subduction. When this happens, the oceanic crust sinks within the mantle, because it is denser than the continental crust.

As the oceanic crust subsides, both temperature and pressure increase. Because the oceanic crust is formed under the sea, a lot of water is present in the rocks. Due to high temperature and pressure, water starts separating from the oceanic crust and this water gets mixed in the mantle over the continental plate. Now the rocks in the mantle begin to melt at the subduction zone and take the form of magma. Magma rises to the surface and ejects from the volcano as lava .

hot-spot volcano

Although most volcanoes form at the boundaries of plates, not all. Some volcanoes also occur at hotspots between plates, for example the Hawaiian Islands. 

Hotspots are those places on the Earth’s surface where volcanoes form far away from the boundaries of the plates. They form in exceptionally hot centers called mantle plumes. Mantle plumes mean the rising of magma within the Earth’s mantle. In the scientific model, the plumes of these molten rock are shown in the shape of a lava lamp. In which there is a rising bulbous head with a long narrow tail, which arises from the cover.

As the plume head reaches the lithosphere, it expands into the shape of a mushroom with a diameter of about 500 to 1000 km.

Scientists are not yet unanimous about how the hotspot is formed. The most prominent theory, put forward by Canadian geophysicist J. Tuzo Wilson in 1963, is that hotspot volcanoes form from stable hot areas, especially deep beneath the Earth’s mantle.

Recent studies suggest that these hot spots may be at shallower depths in the Earth’s mantle and may have migrated slowly over geologic time, rather than remaining constant in one location.

Some scientists believe that hotspots form where magma rises up through cracks in the Earth’s surface. Another theory states that hotspot volcanoes form in long chains, as they together generate cracks on the Earth’s surface.

Scientists do not know which of these theories are right and which are wrong. Some hotspots may be formed on plumes and some on cracks.

classification of volcanoes

Volcanoes are mainly classified into three parts:

  1. active volcano
  2. dormant volcano
  3. dead or silent volcano

Active Volcano – A volcano that is currently erupting, or is likely to erupt soon, or if smoke, gas or lava is coming out of it and there are signs of earthquake, then it is called an active volcano.

Dormant or Dormant Volcano –  Volcanoes that have not erupted for a long time but are likely to erupt in the future, are called dormant or dormant volcanoes.

Dead or Calm Volcano – Those volcanoes which have erupted thousands of years ago and there is no possibility of their eruption in future, are called dead or silent volcanoes.

type of volcano

The volcano is divided into five parts:

  1. cinder cone
  2. composite volcano
  3. shield volcano
  4. lava dome volcano
  5. punk volcano

cinder cone

Cinder cones are spherical or oval cones that are formed from small fragments and droplets of frozen lava emanating from a hole. As the lava along with the gas rises into the air, it breaks into small pieces and starts falling around the hole in the form of solid embers. The faces of most cinder cones are bowl-shaped at the summit. Most cinder cones explode only once. They can form in the form of holes next to a large volcano or on their own.

composite volcano

Compound volcanoes, also called stratovolcanoes , are volcanoes with steep edges that are made up of multiple layers of volcanic rock. They are usually made of thicker and more viscous lava, ash and rock debris. These volcanoes are high conical mountains formed by layers composed of lava flows and other ejected material, called strata, from which the name stratovolcanoes originated.

Compound volcanic lava consists of fragments (embers), ash and lava. These solid fragments and ash clump together to form piles where lava flows over them and hardens as they cool. In this way, this process continues and layers are formed. Combined volcanoes can be extremely catastrophic and cause catastrophic eruptions.

shield volcano

Shield volcanoes are shaped like a bowl or shield (shield) from the middle which is made up of basaltic lava flows with long gentle slopes. They erupt with less thin lava that can extend over long distances from the hole. They don’t usually explode catastrophically. In these, there is less silica due to the lava being less thick. Shield volcanoes form more in oceanic regions than in continental regions. The Hawaii Volcanoes are a chain of shield volcanoes and are also common in Iceland.

Lava dome volcano

A lava dome occurs when erupted lava is very thick. This volcano forms a mound with steep edges in the form of a pile of lava near the hole. It is formed by the slow eruption of thicker and viscous lava. Sometimes it is generated along with the mouth of an earlier volcanic eruption. Such volcanoes can cause violent and catastrophic eruptions like combined volcanoes, but the lava emanating from them does not spread very far.

molasses or punk volcano

Garamukhi is said to be those volcanoes where hot liquids and gases rise under the earth to form a mound on the surface and slurry (wet soil) and debris come out from its mouth. They are kept in the category of volcanoes, although they do not emit lava and the temperature is lower than volcanoes. 700 Garamukhi are known all over the world. The height of the highest Garamukhi is about 700 meters, which is spread over 10 kilometers in diameter. Most of the liquid that comes out of these volcanoes is water. The gases released from them include 85% methane and other gases carbon dioxide and nitrogen.

What is a volcanic eruption?

As we know, when a volcano erupts, a hot fluid comes out which includes lava, gas and ash. This material is deposited in the form of magma when the rocks melt in the underground mantle. When this magma emanating from the volcano becomes thick, then the gas bubbles are not able to escape easily and the magma increases, due to which the pressure also increases. When the pressure becomes extremely high, magma ejects from the volcanic vent with a large eruption, which is called a volcanic eruption.

Eruptions in a volcano can also be very fierce, whose sound can be heard thousands of kilometers away. One such explosion occurred on August 26, 1883 in Krakatoa, Indonesia, whose sound was heard in Australia, about 4800 km from there. 

If there is less gas and more lava in the material emanating from the volcano, then there is not much sound from the explosion. These are quiet types of volcanoes. An example of this is the Monalova volcano of the Hawaiian Islands. The lava comes out in large quantities from them and spreads far from the volcanic hole. The Vesuvius volcanic eruption in 1979 near the city of Pompeii, Italy, was of this type. The lava emanating from this volcano covered the entire city of Pompeii. Later excavations found the ancient remains of this city, including the bones hidden below and many other items of use.

types of volcanic eruptions

The types of volcanic eruptions depend on many factors, such as the chemistry of the magma, the temperature and viscosity of the magma, the presence of underground water, water and gas content. The different types of volcanic eruptions are shown below.

Hydrothermal Eruption – In this type of eruption only gas is involved and no lava is released. These are generated due to the heat created in the hydrothermal system.

Strombolian and Hawaiian Eruptions – Hawaiian eruptions are those explosions that cause a shower of fire and Strombolian eruptions are those from which small fragments made of lava are released. 

Fretomagmatic eruptions – These eruptions occur when newly formed magma and water come into contact with each other.

Phrytic eruptions – These eruptions occur when the heat of magma interacts with water. Such eruptions release water, vapor, ash and lava.

Vulcanian eruptions – These eruptions are of short duration and can reach a height of 20 km.

volcanic material

Generally three types of substances come out of a volcano:

  • Liquid substance
  • gas and water vapor
  • solid material

Gas and water vapor – Many types of gases are released with the eruption of volcano, which include water vapor and carbon dioxide, sulfur dioxide, hydrochloric acid, carbon monoxide, ammonia chloride etc. 

Solids – Solids, such as cinders, ash, clay, etc., are formed from the lava of the volcano. 

Fluid – The fluid formed by the melting of rocks in the mantle beneath the earth is called magma. When this magma comes out of the volcano, it is called lava. 

With the eruption of a volcano, the first gases come out of the earth’s surface. The highest amount of vapor is found in these gases. Along with this, some solid materials like rock fragments, dust particles and ash come out. Due to the high intensity of the gas during an eruption, the solids rise to great heights, and when the intensity of the gas decreases, they fall back to the surface. The molten fluid that comes out during eruption is called lava.

volcanoes of india

Barren Island – This is the only active volcano in India, which is spread for about 3 kilometers. In the year 2017, again lava was seen erupting from this volcano. Earlier it had exploded in May 2005. This island is located in the Bay of Bengal in the northeast, about 138 km from Port Blair, the capital of the Andaman and Nicobar Islands.

It is the only active volcano not only in India but also in South Asia. These volcanoes are found where there is more pressure in the tectonic plates or there is more heat under the land. The first volcano on the island erupted in 1787. Since then the volcano has erupted 10 times here. Baron means barren, that is, where no one lives. No one lives on this island, so it is called Barron’s Island. It is a form of composite volcano.

Deccan Trap – Deccan Elevation or Deccan Trap is a region located in the western part of India. Many years ago a volcanic eruption took place at this place, which formed basalt rocks and black regur soil was formed on them. This soil formed due to the release of lava is also called ‘lava soil’. It is counted among some of the largest volcanically formed landforms in the world.

Baratang Island – also known as Baratang, is an island of the Andaman archipelago in the Andaman and Nicobar archipelago of India, located in the Bay of Bengal. Garamukhi Volcano was found on this island, which is active since the year 2003. 

Narcondam Island – This island is an island in the Andaman Islands group of India. It is the earliest island in India, whose main peak is about 710 meters above sea level. The Geological Survey of India has classified it as a dormant volcano, as it has been quiet for hundreds of years.

Dhanodhar Hills – These hills are some of the hills located near Nani Aral village present in Kutch district in Gujarat state of India. Dead volcano is found here i.e. dormant volcano. Its height is about 386 meters.

Dhosi Hills – Dhosi Hills is a dormant volcano which is present in the north-western part at the extreme end of the Aravalli mountain range . Its altitude is 740 meters above sea level. This hill has also been mentioned in religious texts like Mahabharata and Puranas. Even though it exists with the structure of a dormant volcano, geologists refuse to consider it a dormant volcano. According to him, there has not been any kind of volcanic eruption here for the last 2 million years, so it is not appropriate to consider it as a volcanic structure.

major volcanoes of the world

The names of some of the major volcanoes of the world are as follows: 

Mount Cotopaxi ActiveEcuador
Mount EtnaActive Italy
vesuvius dormantItaly 
monaloaActiveHawaiian Islands
in fuzea ActiveJapan
mount rainierActiveUnited States of america
Mount KilaueaActiveUnited States of america
Pope quietMyanmar
Mount Cameron ActiveAfrica
mount erbush Activeantarctica
chimborazo quiet Ecuador
el mistydormantGuava
mount pintuboActivePhilippines
Barren Island VolcanoActiveAndaman and Nicobar Islands
Narcondam Island VolcanodormantAndaman and Nicobar Islands
aconcagua quiet South America
Mount Damavandquiet Iran
Koh quiet Iran

Volcano FAQs

Which is the largest volcano in the world?

Mauna Loa is the largest volcano in the world.

Which is the largest volcano in Asia?

Mount Damavand is the largest volcano in Asia.

What is the definition of volcano?

A volcano is a crack or hole on the Earth’s surface that ejects a hot fluid, including lava, gas, and ash from beneath the Earth. 

Where are the world’s most active volcanoes located?

The world’s highest active volcano is found on Mount Kilauea in Hawaii.


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