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Volcano

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Last updated date: 29th Feb 2024
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What is a Volcano and What are its Various Types?

The volcano definition can be put as a generally conical landform like a hill or mountain with a vent (or opening) from where materials like lava, volcanic ashes, and other gasses erupt. One of the major reasons behind the volcanic eruption is the pressure that is created due to the dissolved gasses. In other words, a volcano eruption can be seen as similar to that of opening a bottle of soft drink, where the pressurized gasses spew outwards. In other words, a volcano can be defined as an opening in the crust of a planetary-mass object from which hot lava, volcanic ash, and gasses come out via a magma chamber under the surface.


One of the volcanic mountain examples is Mount Garibaldi. This is a potentially active volcano that is located southwest of British Columbia.

Formation of Volcanic Mountains

The formation of volcanic mountains takes place from the surface eruption of magma. This is mainly present in Earth’s upper mantle. Once the magma erupts, it comes out to the surface, forming lava that flows, depositing ashes. The formation of mountains takes place, as continuous eruption takes place, and new layers of lava are added on top of each other. You can also say that volcanoes usually occur when there is a tectonic movement on the surface of Earth with the majority of these volcanoes being formed under the water surface. For instance, divergent tectonic plates create volcanoes along a mid-ocean ridge like the Mid-Atlantic Ridge, but convergent tectonic plates cause volcanoes in the Pacific Ring of Fire. The phenomena of extension and thinning of crustal plates can also cause volcanoes to form, like the ones in the East African Rift and the Wells Gray-Clearwater volcanic zone in North America, as well as the Rio Grande Rift. Upwelling diapirs from the core-mantle barrier, 3,000 kilometers (1,900 miles) deep in the Earth, are thought to cause volcanism distant from plate boundaries. Hotspot volcanism, such as the Hawaiian hotspot, occurs as a result. When two tectonic plates slide past each other, volcanoes are rarely formed. 


Large eruptions can change air temperature because ash and sulfuric acid droplets obscure the Sun and chill the Earth's troposphere. Volcanic winters have traditionally followed large volcanic eruptions, resulting in devastating famines.


The Different Stages of Volcanoes

One can extract more information about volcanic mountains after learning the different stages of formation. The shape of the volcanic mountain tends to differ based on the following circumstances:

  • The kind of material erupted from the volcano

  • The exact kind of eruption

  • The overall change after the eruption

Categories of Volcanoes

Active Volcanoes: The volcanoes that are labeled as active volcanoes have the tendency to erupt at any given point in time. There are similarly active volcanoes that are erupting already.

Dormant Volcanoes: Dormant Volcanoes are the ones that have not erupted for a long time, but they are expected to erupt in the distant future.

Extinct Volcanoes: The volcanos which have not erupted for tens of thousands of years and are not likely to erupt in the future are generally termed extinct volcanoes.

How Does Volcanic Eruption Occur?

If you are wondering how volcanic mountains are formed, they occur in the following way. At first, during the eruption, magma or molten rocks rise above the surface. The formation of magma takes place when the Earth’s mantle melts. Such melting occurs due to the high pressure exerted on them. Such pressure is caused by the movement of tectonic plates, either pulling apart or pushing towards one another.


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Magma is generally lighter than rocks. So, as the magma gradually rises to the floor, bubbles start to form within. Runny magma, on the other hand, erupts from the vents that are formed within the Earth’s crust, before even flowing over the surface. When too much pressure is formed during volcano formation, it rises with an explosive eruption. The magma which flows out and comes in contact with air is called lava.

Types of Volcanoes

There are many types of volcanoes that have a variety of shapes and sizes. Generally, one can find five major types:

  • Cinder Cone Volcanoes

  • Composite Volcanoes

  • Shield Volcanoes

  • Lava Domes

  • Supervolcanoes 


Cinder Cone Volcanoes

These are the simplest volcanoes to be formed. The cinder cone volcanoes are formed when small particles and other blobs of lava eject out of the volcanic vents. The lava spews into the air and small pieces of the same gather around the vent. As time passes by, it gradually forms a bowl-shaped crater. Another important aspect of the volcano is that these mountains hardly grow larger than 1000 feet. Eg. Mauna Loa Volcano, Hawaii. These are known to be the most common type of volcanoes and their shape is similar to that of a composite volcano, although these are much smaller. Cinder cones are rarely taller than 300 meters, but they have steep slopes. Cinder cones grow quickly, often during a single eruption cycle. Cinder cones are made up of small rock fragments heaped on top of one another, such as pumice.


The boulder flies through the air and lands not far from the vent. The composition of the lava erupted by the volcano determines the specific composition of a cinder cone. A crater is common on the summit of cinder cones.

Composite Volcanoes

Some of the most renowned mountains are made out of composite volcanoes. They are often termed stratovolcanoes. Mount Fujiyama and Mount Cotopaxi are some composite volcanic mountain examples. The conduit systems built within the mountain help them to channel the magma from the Earth’s crust. They are built of many layers of pumice, hardened lava, and ash. 


Composite Volcanoes are the type of volcanoes that are made up of several different intermediate rocks that make up composite volcanoes. Volcanic eruptions at these volcanoes are usually intense due to the viscosity of the lava. The viscous lava hardens on the surface of the volcano and forms steep slopes as it cannot go down the flanks. The volcano is formed layer by layer as ash and lava solidify one on top of the other. As a result, composite volcanoes have the traditional cone shape. A composite volcano's cross-section shows alternating layers of rock and ash: magma chamber, bedrock, pipe, ash layers, lava layers, lava flow, and so on.

Shield Volcanoes

These volcanoes have a shield-like shape when observed from above. They are made of fluid lava flows and due to highly fluid lava, which travels far from the site of eruption. Since they stretch over a long distance and eventually solidify, there is a slow accumulation of broad lava sheets giving a distinct form to this volcano. A good example of such a mountain is the Volcán Wolf. 


Shield volcanoes are so named because of their form. Shield volcanoes are not particularly steep, although they can be rather massive. At spreading centers or intraplate hot zones, shield volcanoes are common. Lava that is fluid and flows readily forms shield volcanoes. The spreading lava creates the shield. Shield volcanoes create several layers over time, and the strata are typically similar in composition. Due to their low viscosity, shield eruptions are likewise non-explosive.

Lava Domes

Finally, there are the lava domes. These are formed from small masses of lava that stay in one place. Due to their more viscous nature, they become too thin to even move from one place to another. The only way these domes can grow is through the accumulation of lava building up inside them. Lava domes tend to explode violently, as a result of which, it creates a large chunk of hot rocks and ashes. Eg. Atwell Peak, British Columbia.

Super volcanoes

The supervolcanoes are very rare if we talk about the past. It's a good thing, too, because they're enormous. A supervolcano must erupt more than 1,000 cubic kilometers of material (240 cubic miles). Supervolcanoes can be the most harmful volcanoes. There is not much information available about supervolcanoes as this is a new concept. It's still unclear what causes supervolcano eruptions. Scientists believe, however, that a massive magma chamber bursts in a single catastrophic explosion. Calderas arise when the surface collapses, producing a big pit. 

FAQs on Volcano

1. State the Difference Between Lava and Magma?

Going deep into volcano details, Lava and Magma are two terms that are very loosely used similarly. Magma can be defined as the liquid rock that builds up inside the volcano. Lava is the liquid rock that flows out of the volcano and comes in contact with air. If you look at freshly drawn out lava, they are generally red to white-hot in color. One of the major reasons why lava takes such a long time to cool is due to poor conductivity. Their vicious nature results in a very slow flow while slowing down the hardening rate at the same time.

2. What are Lahars and Pumices?

Both lahars and pumices are different components of volcanoes. Lahars can be defined as the flow of debris that mainly comprises pyroclastic materials. While flowing down from the mountain, they take the shape of a river. Lahars are as dangerous as the lava itself. While they are moving, they retain their liquid state, but as they stop, it solidifies. Pumice, on the other hand, is a kind of lightweight, porous volcanic rock. They are mainly formed during volcanic eruptions. Their shape greatly resembles that of a sponge, due to the gas bubbles that get frozen inside them. It can be formed out of any magma.

3. What are the different categories of volcanoes? 

There are three basic categories of volcanoes and these are active volcanoes, dormant volcanoes and extinct volcanoes. Active volcanoes are those volcanoes that are currently erupting or that can erupt at any time. Dormant volcanoes are those kinds of volcanoes that are currently inactive but these volcanoes can become active and can erupt in the near future. Extinct volcanoes can be described as those volcanoes that have not shown any kind of activity for a long long time (thousands of years) and these volcanoes are not expected to erupt in the future either. 

4. How do the different shapes of a volcano form? 

There are a lot of reasons behind the formation of different shapes of a volcano. To understand this, we can consider several factors like what kind of material came out of the volcano at the time of the eruption, what changes took place in the volcano after it erupted and what type of eruption did exactly take place in that volcano. All these factors tend to determine the shape of a volcano. 

5. What are cinder cone volcanoes? 

There are a lot of types of volcanoes and a cinder cone is one among them. This type of volcano is the most common one and is the simplest of all. It is formed by the eruption of lava in the form of small drops, from the vents. The lava keeps erupting and small particles and blobs of this lava keep on gathering around the vent. With time, small pieces of lava tend to create a crater around the vent.

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