Volcanoes-General Facts

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A volcano is an opening in the Earth’s crust, which allows hot ash or magma and gases to escape from below the surface.

Where are they generally found?
Volcanoes are generally found where tectonic plates are converging or diverging.
A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates
coming together.
Although volcanoes can also form where there is stretching or thinning of the Earth’s crust like in the African Rift Valley. Volcanoes are also found in space.

Different types of volcanoes:

There are 4 main types of different volcano, these are: Stratovolcanoes, shield, cinder cones and spatter cones.

These are formed by layers of rock or strata. There is no distinct shape for a stratavolcano as they come in all different shapes, however the sides are generally steep.
Examples of stratovolcanoes: Mt. St. Helens, Mt. Fuji and Mt. Etna.
A stratovolcano can look very nice when it is dormant, but when they erupt, it is not very safe to be around. As magma rises, it tends to get clogged due to a high viscosity, this therefore makes the pressure needed to force out the magma HUGE. This then means that the explosion is very large with both rock and lava

Shield volcanoes
Shield volcanoes are big aswell. These are made up of numerous layers of flowing lava. There are hot spots usually in the centre of the volcano. Explosions are frequent, but are not generally highly explosive. Although all volcanoes are dangerous to be near when erupting, these are particularly good to watch. Lava spray is uncommon in these types of volcanoes. These can form from the ocean floor, they gradually build height through a steady stream of magma.
Examples of shield volcanoes:
Mauna Loa and Kilauea


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