A volcano is a mountain that is connected directly to molten rock below the earth’s surface. Eruptions occur when pressure builds up and rock, gases, ash and lava shoots from it. A volcano is considered “active” if it actually erupts or gives off gases frequently. Earthquakes in the area of the volcano are also a sign that can cause it to be considered “active”. If a volcano has not given off any gases or caused any earthquakes for some time, it is labeled as “dormant”. However, this does not mean it will not erupt again in the near future. In fact, a volcano that has not erupted in tens of thousands of years is considered “dormant”. An “extinct” volcano is one that no longer has a magma supply. A volcano can take a million years – or even more – to become extinct.

Formation of volcanoes and eruptions

Magma under the earth sometimes gets to the surface. The result is an eruption that can have catastrophic results. The more a volcano erupts, the bigger and bigger it will become. Eruptions are caused when the crust of the earth – called “plates” – move around, causing serious levels of friction. This friction causes volcanoes to erupt.

Effects of volcanoes

Volcano eruptions can have serious after effects. Particularly violent eruptions in history have caused significant changes in the earth’s temperature, causing brutal winters which led to widespread famine. Another consequence of an eruption is the toxic gases released into the air. These gases are dangerous to life. Ash can cause very poor visibility, which is detrimental to aircrafts. Most obviously, volcanic eruptions can wipe out entire villages, forests and landscapes, as lava flows are incredibly hot and move very quickly.


On an Indonesian island in 1883, a volcano erupted that had greater force an atomic bomb. The sound of rock and ash being spewed forth was heard from thousands of miles away. It destroyed a nearby town entirely, killing its inhabitants instantly. This island, called Krakatoa, eventually went into the sea, but a new island was spotted in its place around 1927.

Clearly volcanoes can have negative effects of massive proportions, including loss of human life and serious property damage. Fortunately, there are better methods of warning vulnerable populations of impending eruptions and this lessens the likelihood of fatalities.

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