What Types of Volcanoes are there?

You have seen the ways in which volcanoes erupt, and we have already said that volcanoes are not always the simple cones that one usually associates with outpourings of red hot, molten rock.

In fact, eruptions vary a great deal in the type of products that are spewed out, in their intensity, and in the form which the volcanic vent takes.

Types of volcanoes

  • Fissure eruption
  • Hawaiian volcano

Fissure eruption: First of all there is the type which is known as the fissure eruption. This is simple to describe. Her flood of lava pours out of a crack in the Earth’s crust and flows very freely. When it cools, it hardens into an almost flat sheet. This type of eruption is also known as the Icelandic type, because of the type of lava flows commonly found there.

Hawaiian volcano: In the Hawaiian type of volcano, so called for obvious reasons, lava pours out of a pit-like crater, and gas is quietly released most of the time.

Occasionally, however, there is a sudden spurt of the volcanic gases blowing out a spray of glowing, burning droplets of lava. The well-known Pele’s hair is caused by these droplets being caught in the wind and stretched into threads.

Typical examples of the main types of volcanoes.

If the lava cannot flow easily (and this occurs when the composition of the magma is richer in silica), the gases have more difficulty in bubbling off.  They are only released when the pressure builds up enough to force the gases out.

In This  kind of  eruption, which  is known  as the Strombolian  type  after  Stromboli, Sicily, the volcano erupts from  time to time  carrying  lumps  of lava or volcanic bombs. Sometimes there are also lava flows.

If the lava is very thick and almost solid, great gas pressure is needed before it is released. When  it does  erupt  it does  so with  explosive  and terrible  force, so that hot  ash and fragments  of lava  are thrown  high  into  the air.

This is known as the Vulcanian type, the characteristic cone is developed. There are other types of central volcanic types, that is, where the eruption is from one main centre.

A vent of a volcano may become plugged with solidified lava. When the cone is eroded away the plug or neck remains, like this one at Le Rocher-St-Michel in France.

Vulcanology is a very complex study, and for the more adventurous can be an extremely dangerous one, involving climbing to the very top of an active volcano.

Under  these conditions,  even if the  volcano is not  actually  erupting the  ground  may be so hot  that it burns  the shoes of  the scientists  and the gases  may be almost  suffocating. Workers have actually looked into open craters into the bubbling, burning lava above.

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