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Last Updated: Thursday April 29 2010 10:40 GMT

Volcanoes - Fascinating facts!

A diagram of the earth's crust

When a volcano in Iceland erupted in April, it caused huge disruption in parts of Europe.

Lots of British tourists were stranded abroad and couldn't get home because it was too dangerous for planes to fly through the huge ash cloud the volcano emitted.

Check out our volcano facts by clicking on the questions below...

* Volcanoes: the facts

* The eruption in Iceland

* An even bigger volcano

* The disruption caused by the volcano in Iceland

* How volcanic ash affects aeroplanes

* Famous volcano eruptions

• A volcano is a piece of land (usually a mountain) which molten rock (magma) erupts from

• They're like safety valves that release the pressure that builds up inside the Earth

Lava that flows from volcanoes is so hot it burns everything in its path
Lava that flows from volcanoes is so hot it burns everything in its path

• 300 million, or 1 in 20, people in the world live within 'danger range' of an active volcano

• About 1,500 different volcanoes have erupted over the past 10,000 years, but only about 60 erupt each year. On any given day, there are about 20 volcanoes erupting somewhere in the world

• Some volcanoes are under the sea

• In the past 500 years, 250,000 people have been killed as a direct result of volcanic eruptions

The world's largest active volcano is Mauna Loa in Hawaii
The world's largest active volcano is Mauna Loa in Hawaii

• The Earth's rigid outer layer is made from huge slabs called tectonic plates that fit together like a jigsaw puzzle. When two of them collide, one is pushed below the other, causing melting at depth that leads to volcanic eruptions when the molten rock (magma) finds its way to the surface

• Volcanoes can also erupt at sites where two plates are being pulled apart, like Iceland, or at special 'hot spots' like Hawaii

• The world's largest active volcano is Mauna Loa in Hawaii

• Lava flows can reach 1,250 degrees Celsius and burn everything in their path - a glass thermometer would just melt if you tried to measure it

Volcano erupts in iceland
The volcanic eruption in Iceland

• Ash and toxins from eruptions can be dangerous and cause lung damage, particularly for babies and old people

• People often set up home on the slopes of volcanoes because the soil there is rich and fertile

• 90% of all volcanoes are in the 'Ring of Fire' which is along the edges of the Pacific Ocean

• The word volcano probably comes from the name of Vulcano, which is an island off Sicily named after Vulcan, the Roman God of Fire

• Maelo birds use volcanoes to hatch their eggs! They bury them in volcanic sand and when the chicks hatch they claw their way up to the surface

• It's in south-west Iceland, it's near the sea, and it covers around 40 square miles

• It's 1,666 metres tall

• The volcano has erupted TWICE. Once in March 2010, which meant 500 people were evacuated from the area, and then again in April (much more powerful than the March eruption) which caused Europe so much disruption

The Eyjafjallajökull volcano erupts in Iceland
The Eyjafjallajökull volcano erupts in Iceland

• It's underneath a glacier which causes two problems: 1) flooding when the heat from the volcano melts all the ice, which is why those people were evacuated, and 2) it makes the eruption highly explosive. When the water leaked into the insides of the volcano, the magma turned the water to steam. The resulting explosion shattered the magma into tiny fragments called 'volcanic ash' and shot them high into the sky

• The ash cloud reached 55,000 feet

• Iceland is a volcanic hot spot on the Mid-Atlantic Ridge, which is the dividing line between the Eurasian and North American plates

• There are 35 active volcanoes in Iceland

• There is another volcano nearby and people are worried this eruption could set it off. It's called Katla

• Katla is around 25km away from the other one

• It's got a much bigger magma chamber so it's far more powerful

• Each of the eruptions of Eyjafjallajöekull in the years 920, 1612, and 1821-1823 has been followed by an eruption at Katla

• On 20 April 2010, Icelandic President Olafur Grimsson said: "The time for Katla to erupt is coming close… we have prepared… it is high time for European governments and airline authorities all over the world to start planning for the eventual Katla eruption."

• It could cause more disruption in Europe, but also major flooding in Iceland

• British airspace was closed for six days, which meant no planes could fly at all

British airspace was closed for six days
British airspace was closed for six days

• 120,000-150,000 Brits were stranded abroad, including loads of teachers and pupils on their Easter holidays

• The disruption has cost airlines across the whole world £1.1 billion

• 1.2 million passengers a day were affected by the closure

• Volcanic ash is formed from explosive eruptions with particles as hard as a knife blade

• It contains tiny bits of rock and glass which can wreck planes if they suck it into their engines

Aeroplane engines can be damaged by volcanic ash.
Aeroplane engines can be damaged by volcanic ash

• The ash can also melt once it's inside the engine and then solidify again, which also wrecks them

• In 1982, a BA flight from London to New Zealand lost all four of its engines when it flew through a volcanic ash cloud. It glided without power for more than 15 minutes before they managed to restart some of the engines. The ash cloud hadn't shown up on weather radars because it was still dry, and the equipment can only spot cloud moisture

• The worst volcanic disaster of the 20th century is considered to be the eruption of Mt. Pelée in 1902. It was on the island of Martinique in the Caribbean and killed 30,121 people. Only two people survived: a shoemaker living on the edge of the island and a prisoner who had been locked in a dungeon cell with thick stone walls

When Mount Vesuvius erupted near Pompeii
When Mount Vesuvius erupted near Pompeii

• The Lake Toba supervolcanic eruption nearly 75,000 years ago in Indonesia plunged Earth into a volcanic winter - known as the Millennium Ice Age.

• In A.D. 79, Vesuvius erupted violently, devastating the towns of Pompeii and Herculaneum. The remains of people were preserved by the ash deposits and you can still see them today

• Krakatau in Indonesia in 1883. The blood-red sunset could be seen as far away as Norway. It released 200 megatons of energy, the equivalent of 15,000 nuclear bombs. Even though the island was uninhabited, the eruption killed 36,000 people as the result of burning ash showers and huge tsunamis. It generated the loudest sound reported in history

Krakatau erupted in Indonesia in 1883
Krakatau erupted in Indonesia in 1883

• The 1815 volcano Tambora in Indonesia was the biggest observed by humans and killed more than 70,000 people

• The most lava ever recorded from a single eruption in the past few hundred years was the 1783 Laki eruption in Iceland. Though there was no single big explosion, the eruption killed a quarter of Iceland's population by producing poisonous gases and clouds of ash that resulted in widespread crop failure and starvation