How Volcanoes can be classified

How Volcanoes can be classified

Posted by Manisha on May 15, 2020

Whenever we talk and think about a Volcano, the first image that comes to mind is a catastrophic Hollywood animated worthy explosion of red hot magma and lava through a vent with a boom blast burst sound.

The study of volcano comes under the Geomorphology, Geology branch of Geography as its especially and directly related to Earth’s crust.

However, as the volcano provides the open passage to the Earth’s interior, our Geologist and professional volcanologist dig out more information, used in the mapping of active volcano areas, forecasting of possible volcanic eruptions and earthquake.

So, on the basis of the collection of information and after compilation of it, our Geologist and Volcanologist classify volcanoes, in order to know it’s nature, structure, shape, size magnitude, time of the eruption, and material, into mainly three broad categories.

Classification of Volcanoes on 3 different basis

  • On the Basis of Time
  • On the Basis of Volcanic Topography or Shape
  • On the Basis of Vent size

Now going to discuss each category one by one in detail.

On the Basis of Time

There are further three more divisions of the volcano, on the basis of it’s eruption time. These are:

1. Active Volcanoes

These are those volcanoes through which volcanic eruptions like lava, magma, ashes, etc. keep on erupting very often. Its vent is always opened.
For example, Italy's Etna volcano, which is active from last around 2500 years, Sisley Island Stromboli volcano erupt each after 15 minutes.

2. Dormant Volcanoes

This kind of volcanoes is quiet from last so many years but there is always a chance to erupt any time in the future and cause major destruction of life and to the economy of a country.
For example, Italy Vesuvius volcano suddenly erupted in 1931.

3. Extinct Volcanoes

In this kind of volcanoes, there is no chance to erupt in the future.
Their mouth (vent/creator) is closed now and filled with water and became a volcanic lake.
For example, Papa volcano of Myanmar is a good example of this.

On the Basis of Volcanic Topography or Shape of Volcano

According to this we can further divide it into four types. These are:

1. Cinder Cone
  • It is simple, the most common type of volcano erupts with a single vent.
  • It is a steep conical hill, built from particles and blobs of congealed lava.
  • It is symmetrical in shape.
  • Also known as Scoria cone and Spatter cone, whereas some called it ash cone.
  • It is developed from the explosive eruption of heavy, dark, ferromagnesian, and intermediate lava, generally found along the flanks of shield volcanoes and deposits around a volcanic vent, forming a crater at the summit.
  • It is generally small in size around 300 feet (91 meters) tall and not rise more than 1200 feet (366 meters).

For example, Lava Butte, in Newberry National volcanic monument, Oregon; Mount Omuro in Honshu, Japan, Cocoa crater of British Columbia, Kostal cone of Canada.

2. Shield Volcano
  • As its name shows the image of a protection shield resembles an ancient warrior’s shield lying on the ground.
  • It is a wide and huge volcano with shallow or gentle sloping sides.
  • The gentle slope is around (usually 2 degrees to 3 degrees), gradually steepens with elevation 10 degrees approximately.
  • It is built of very thin lava, spreading out in all directions through a central vent.
  • Generally not explosive in nature but are more like liquid overflowing around the edges of a container, here full of hot lava.

For example, Mauna Loa of Hawaii volcano is the world’s largest volcano.

3. Stratovolcano or Composite volcano
  • Here the “strata” stands for “many layers” and also called composite because of its composite stratified structure built from the sequential outpouring of erupted materials like lava, ash, tephra, pumice, magma.
  • It’s a conical shaped with steep sides volcano, built by a layer of erupted and suddenly hardened lava, magma, pumice, ash, and tephra.
  • It consists of alternating layers of hardened volcanic erupted material flows.
  • Its shape is a symmetrical cone with steep sides which may rise up to 8000 feet.

For example, a modern example of this is- Mount Saint Helens and Mount Pinatubo.
Other examples are Mount Vesuvius of Italy, Krakatoa of Indonesia, and many more.

4. Lava or volcanic Domes Volcano
  • It’s very clear with the name that it is a circular mound-shaped protrusion.
  • It is the high viscosity of the lava that prevents it from flowing far away from the vent.
  • This is formed by a viscous magma, lava, being erupted effusively on to the surface of earth and piling after hardened up around the vent.
  • Around 6% of eruptions on earth are lava dome forming.
  • Some lava dome structures have been suggested found on the moon, Venus, and Mars planet.

For example, Chaiten Lava dome of Chile, Galeras lava dome of Colombia, Black Butte of United States.

Do you find any volcanic topography in your region or country? Which category of volcano type does it belong to?
Write to me with the answers to these questions. Also, inviting your queries, experiences, views for the same. 

On the Basis of Vent Size

On this basis volcanologists and geologists divide volcanoes into two types. But the question arises about the vent. To understand this first we should know about the vent first.

What is volcanic vent?

The volcanic vent is the openings on the Earth’s crust (surface of the earth), through which lava and pyroclastic flows are erupted or ejected.
This vent is connected underneath the surface of the Earth where the liquified rocks or magma is present in molten form, due to a great increase in pressure, and over time, it burst out through the vent, on the surface of Earth’s crust.

1. Central Vent Volcano
  • It is a very common type of volcanic vent, in which only one opening like a conduit pipe is there, through which volcanic material erupted.
  • The eruptive products are accumulated, thicken, and hardened around the vent and build up a low-angle shield or high-angle cone-like topography which is constituting the volcanic pile.

For example, Hawaii type, Strombolian and Volcanism type, Vesuvian type, Plinian type.

2. Lateral or Linear or Fissure Vent Volcano
  • It is also named as fissure eruption, volcanic fissure, fissure Vent because here the eruption of volcanic material occurs not through a single vent but through a linear or long opening on Earth’s crust.
  • This may cause large flood basalt with the run of lava channels and later lava tubes.
  • These opening of fissure Vent are usually found along in rifts and rift zones like East African Rift, in Iceland, and areas of Circum-Pacific ring of fire.

For example, the Bishoftu volcanic field, Quetena Roy mountain, lava channel of Hawaii, etc.
 
In this post, I tried to cover all major types of volcanoes, found all over the world, in very simple words. I'm here for you, to know more and for more interesting cum exciting information about our beautiful planet Earth, stay tuned with me.