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Types of volcano: Types of volcanoes with examples

 

What is a volcano?

  • A volcano is an opening in the earth’s crust through which lava, volcanic ash, and gases escape.

 

Classification of volcano

3 types of volcano: Volcanoes are classified as active, dormant, or extinct. Active volcanoes have a recent history of eruptions; they are likely to erupt again. Dormant volcanoes have not erupted for a very long time but may erupt at a future time. Extinct volcanoes are not expected to erupt in the future.

 

Types of volcanic eruption UPSC

  • When magma erupts as lava at the surface, it forms different types of volcanoes.
  • These volcanoes depend on: the viscosity, or stickiness, of the magma; the amount of gas in the magma; the composition of the magma; the way in which the magma reached the surface.

 

Why are there different types of volcanoes?

  • Viscosity is important in volcanic eruptions. A highly viscous magma produces steep-sided volcanoes, as the viscous volcanic material doesn’t flow that far from where it is erupted.
  • A low viscous volcano, on the other hand, have gentle slopes as the more fluid lavas (basalt) can flow great distances away from the vent to produce broad, gentle slopes.

 

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Types of volcanoes UPSC: How many types of volcanoes are there?

Cinder cones

  • Cinder cones are the simplest type of volcano.
  • They are built from particles of lava ejected from a single vent.
  • “Cinders” are small pieces of igneous rock that have been blown from the vent of a cinder cone
  • As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone.
  • Because cinder cones are made up almost exclusively of loose fragments, they have very little strength. They can be eroded away easily, and relatively quickly.
  • Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet above their surroundings.
  • Example: Cinder cones are numerous in western North America. Moreover, they can be found throughout other volcanic terrains of the world.

 

Shield volcano

  • These are volcanoes which produces low viscosity, and where runny lava spreads far from the source and forms a volcano with gentle slopes.
  • Most shield volcanoes are formed from fluid, basaltic lava flows.
  • Example: Mauna Kea and Mauna Lo. They are the world’s largest active volcanoes, rising over 9 km above the sea floor around the island of Hawai’i.

 

Stratovolcano or composite volcanoes

  • As compared to shield volcanoes, stratovolcanoes have relatively steeper sides and are more cone-shaped.
  • They are formed from viscous, sticky lava that does not flow easily.
  • The lava so formed thus builds up around the vent forming a volcano with steep sides.
  • Stratovolcanoes are more likely to produce explosive eruptions due to gas building up in the viscous magma.
  • Example: Andesite (named after the Andes Mountains), is perhaps the most common rock type of stratovolcanoes, however, stratovolcanoes also erupt a wide range of different rocks in different tectonic settings.

 

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Caldera

  • When a very large, explosive eruption occurs that empties the magma chamber, a place where magma is stored beneath a volcano, the roof of the magma chamber can collapse to form a depression or bowl with very steep walls on the surface.
  • These are called calderas and can be tens of miles across.
  • Calderas can also be formed during an eruption that removes the summit of a single stratovolcano.
  • Caldera-forming eruptions can remove massive portions of a single stratovolcano.

 

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