Classification of VOLCANOES and their types

The volcanoes are primarily responsible for the creation of the lithosphere. Throughout the geological history of our planet, volcanoes have shaped the surface of the earth, have influenced the climate and have played an important role in some moments in the history of the humanity. But not all volcanoes are the same... If you want to discover what types of volcanoes exist and which one is it the classification of volcanoes most used, just keep reading this lesson from a TEACHER!

Index

1. What are volcanoes and what are their characteristics?
2. How are volcanoes classified according to their activity?
3. Translational classification of volcanoes according to their shape
4. Types of volcanoes not included in the traditional classification

Before going into the classification of volcanoes, let's find out what they really are. A volcano is a geological structure which consists of a break in solid surface

From a more traditional point of view, volcanoes can also be defined as follows: A volcano is a geological structure consisting of a conduit that communicates a magmatic deposit with the surface. This conduit is called fireplace. Through the chimney of the volcano the magma rises to the surface, in violent episodes called Volcanic eruptions.

The magma It is a mixture of high temperature containing solids, liquids and gases. The magma that is expelled during volcanic eruptions is called wash. The accumulation of material in the chimney opening creates a conical structure that can become be hundreds or thousands of meters high, at the top of this elevation there is a depression that receives the name of crater.

Although this second definition is more precise, it does not include all known types of volcanoes.

Image: OK Diary

Although there are several ways to classify volcanoes, here we will see the ones that are most useful, depending on whether they are active volcanoes or not, and depending on their morphology. Whatever the type of classification used, we will always find volcanoes that do not respond to any type or others that could be classified at the same time in two categories at the same time.

The classification of volcanoes according to their activity is the next.

Active volcanos

Active volcanoes are considered those that have erupted since the last ice age 10,000 years ago. On Earth they exist, currently between 500 and 1500 volcanoes potentially active, in addition to the countless volcanoes on the seafloor. Among the active volcanoes, a total of 150 volcanoes have erupted during the historical period.

Extinct volcanoes

They are volcanoes that have not erupted and it is not expected to do so in the future, for a long period of time.

There are different classifications of volcanoes according to their morphology. Perhaps the most widespread is the one that classifies volcanoes into three or four morphological types: shield volcanoes, stratovolcanoes, cinder cones, and lava domes. However, this classification does not include all types of volcanoes and also, many authors do not consider the cinder cone as a volcano itself, but as part of a more volcanic structure complex.

The different types of volcanoes according to the traditional classification are as follows.

Cinder cone or slag cones

It is the simplest type of volcano. However, some authors do not consider the cinder cones as authentic volcanoes, but rather as part of other more complex volcanoes.

It is formed by the accumulation of ash and slag around a single volcanic chimney forming a conical structure. Slag fragments form when lava expelled by the volcano cools rapidly in contact with air. The slag fragments have a glassy appearance and contain large amounts of gas bubbles trapped in the rock. The slag and ash expelled by the volcano and cooled by the air fall and accumulate around the chimney forming a conical structure that rarely exceeds hundreds of meters. Most slag cones have a concave depression-shaped crater at the top.

This type of volcano is abundant in eastern North America.

Composite volcanoes or stratovolcanoes

This type of volcano is the most abundant and represents approximately 60% of the total. The main characteristic of compound volcanoes is the existence of a system of conduits through the which magma, stored in a magma chamber deep in the crust, rises to the surface.

In the crater at the top of these volcanoes there is a main chimney or a group of chimneys, but the lava also flows through cracks formed in the walls of the cone. These lava flows solidify in the cracks of the cone, forming very hard edges that contribute to give the volcano cone solidity.

They are volcanoes of great dimensions, with symmetrical cones on very steep slopes. These cones are formed by successive eruptions that have deposited layers of lava flows, slag, ashes and bombs; overlapping.

Some of the largest mountains in the world are compound volcanoes or stratovolcanoes such as Mount Fuji in Japan, Kilimanjaro in Tanzania or Mount Teide in Spain.

Shield volcanoes

It is formed almost exclusively by very fluid basaltic lava that emerges from the volcano's chimney or group of chimneys, flowing in all directions, reaching great distances. The successive eruptions of lava form cones with a flattened shape and a very wide base, similar to the shield of a warrior. Frequently, lava also flows through cracks in the volcano's cone. The Hawaiian Islands are a chain of volcanoes of this type, including the Kilauea volcano, one of the most active in the world.

Lava dome

It is a type of volcano, practically circular in shape, which originates in eruptions in which the lava is very viscous so it does not travel great distances. Lava domes frequently form between the craters of two volcanoes or on the slopes of compound volcanoes. We found lava domes in the Hawaiian Islands and in California.

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Within the traditional classification of volcanoes, there are some typologies that are not contemplated and that, therefore, ignore some types of volcanoes existing on our planet. Here we indicate another classification that, although not the official one, is worth taking into account.

Rhyolite boilers

It is the most explosive type of volcano. Its eruptions are so violent that they cause the volcano to collapse on itself and fail to form elevations characteristic of other types of volcanoes. For this reason they are also known as reverse volcanoes, as they form large depressions or calderas.

The best known example of a volcano of this type is the Yellowstone supervolcano.

Monogenetic fields

These are areas of the earth's crust that show a set of chimneys and cracks (in some cases hundreds or thousands), which are the product of a single volcanic eruption. They do not have the typical appearance of a volcano. They are the result of very small and scattered lava contributions.

Basalt traps or floods

They are large areas in which basalt (silicate or rock rich in iron and magnesium) predominates, similar to those of the oceanic ridges; found in continental areas. Lava flows from these structures can be up to 50 meters thick and thousands of kilometers long. These floods or traps are abundant in Siberia, the Paraná basin or the Columbia River basin.

Mid-ocean ridges

Mid-ocean ridges or MORB for its acronym in English. They are mountain ranges that rise 2000 or 3000 meters above the oceanic plain and on whose ridge there is abundant volcanic activity. In these ridges the magma escapes through fissures and cracks forming new portions of oceanic crust, of the basaltic type.

The rock of the ridges is newly formed and causes the expansion of the ocean floor. This process is the one that currently occurs in the mid-oceanic ridge of the Atlantic and causes the distance between Europe and Africa and the American continent.

Some of the tops of these ridges rise above sea level and create volcanic-type islands like Iceland.

If you want to read more articles similar to Classification of volcanoes, we recommend that you enter our category of geology.

Various authors. (2010).Volcanoes Special nº7. Research and science. Barcelona: Scientific Press S.A.