What are volcanoes?

Volcanoes are openings in the Earth’s surface. Shaped like mountains they let out ash, gas and hot magma in sometimes violent eruptions.

Volcanoes
A basic guide with pictures about Volcanoes.

How does a volcano form?

A volcano forms when two tectonic plates move apart to form a split in the earth's crust. As the plates move apart they allow the magma to come up to the earth's crust creating eruptions.

Volcanoes also appear where two tectonic plates come together. One of the plates is forced down and as it does it melts forming magma that rises through the cracks in the earth's crust.

Some volcanoes can form in the middle of a tectonic plate. Hot spots are under the earth's crust where the magma pushes through to the surface.

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Volcano facts and information
A full guide to Volcanos and how they are made.

Volcano facts
Find out the history of volcanoes, what they look like and the damage they cause.

What is the cause of a volcano?

Volcanos erupt when the red-hot rock called magma under the earth's crust rises up and pushes through the earth's crust. Pressure causes magma to burst out. Once the magma is out it's called lava.

National Geographic Kids - Volcano Facts
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Which volcanoes are still active?

Volcanoes that don't erupt anymore are called extinct volcanoes. Volcanoes that erupt regularly are called active volcanoes. Some of these active volcanoes can go thousands of years before erupting again. The volcano may look extinct but in fact, it is just dormant (sleeping).

What is the Ring of Fire?

The Ring of Fire is the edge of the tectonic plate that the Pacific ocean sits on. A lot of activity around the edge of the plate. About 75% of all active volcanoes are along this edge and 90% of all earthquakes occur here as well.

How are volcanoes measured?

Volcanic eruptions can be measured using the Volcanic Explosivity Index (VEI). The table below shows the VEI scale of eruptions.

Types of volcanic eruptions

There are many types of volcanic eruptions. The Hawaiian is of the most gentle eruptions. Lava is runny so it is a gentle eruption in the form of a fountain. The Plinian is the most violent eruption. Trapped gases cause massive explosions. Huge amounts of ash are thrown high into the air.

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Living near a volcano

It is dangerous to live near an active volcano. Volcanologists monitor volcano activity and can tell when a volcano will erupt. When hundreds of small earthquakes are detected, temperatures increase around the volcano and certain gases are released it is a good sign that the volcano is about to erupt.

People who live near the volcano can then have time to evacuate the area. This reduces the number of lives lost each year, but it's still high being around 1,000 deaths a year.

Negative and positive effects on the environment

The lava flow can create huge devastation to land. Lava can clear large areas of farmland and woodland. The natural landscapes and many homes, villages and towns are sometimes destroyed and changed completely.

The dramatic scenery that the eruptions create can attract tourists and bring money to the area.

Lava and ash provide valuable nutrients which make the soil very fertile for farming. For this reason, many people choose to live near volcanoes. The heat and activity under and around a volcano can be turned into geothermal energy which provides locals with the energy they need for their homes.

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Natural History Museum - London
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