Volcanoes are fascinating mountains that spurt magma from deep inside the earth. Volcanic eruptions vary from small showers of magma to eruptions that can even effect the world’s temperature.
There are two main causes of volcanoes;
- One cause is that some of the magma inside the earth escapes between two of the 17 tectonic plates (the enormous plates inside the Earth’s crust) This usually happens when the plates move.
- The other cause is that magma breaks through a particularly weak or thin tectonic plate.
Once the magma gets past the plates, it, along with some gasses, begin to build up. Eventually, the pressure becomes too big and explodes out of the crust pushing parts of the crust out of the way (which creates the mountain). This process can take thousands of years.
When a volcano has erupted once, it is more likely to erupt again because the magma could follow the already cleared route to the Earth’s surface.
Above left; Tanna volcano, Vanuatu. A composite/stratovolcano,
Above middle; magma pushes crust outwards
Above left; Ambrym Island volcano, Vanuatu. A shield volcano.
Volcanoes can be very destructive, especially in populated areas. As well as producing dangerous gas and lava (magma outside the crust), volcanoes have also been known to cause; earthquakes, landslides, flash floods, acid rain, fire and sometimes tsunamis. These are all caused from the explosion, which can blow up entire mountains, or the magma, that comes out of the crater.
In 1883 a volcanic island called Krakatoa erupted in one of the biggest known eruptions and destroyed the entire island as well as causing a tsunami that wiped out several nearby islands.
There are many different types of volcanoes all caused from underground magma getting passed the tectonic plates. When volcanoes erupt they can cause lots of destruction but they can also be awe-inspiring to watch.
Above; Tanna volcano, Vanuatu.
To measure volcanoes, volcanologists use a device called a sizeometer, which measures the movement of magma beneath the ground.
All volcanoes are measured between 0, not active, and 8, a once in a million year event. The biggest known volcanic eruption (Tambora) was rated 7 and caused a global decrease in temperature.
Although volcanoes are all created from magma escaping the Earth’s crust, there are different types of volcanoes. Some of these are:
· Cinder cone volcanoes; Lava (magma above ground is blown from these volcanoes which lands around the crater creating a hill up to 1km high)
· Composite/stratovolcanoes; These volcanoes are channeled deep into the earth. They can have fissuses of lava. These mounts can get thousands of meters high.
· Shield volcanoes; Shaped like shields and leaking a thin, long river of lava, shield volcanoes are amazing to see and are unlikely to have a major eruption.
· Lava domes; Similar to shield volcanoes, lava domes produce lava. But unlike shield volcanoes, these produce thick lava which turns into rock around the volcano. These volcanoes take a long time to grow larger.
Above; Ambrym volcano, Vanuatu.
ALL SIGHTED ON 16/10/2017
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