Published 19 April 2010
Volcanoes have dominated the world’s headlines in recent days, after plumes of ash from a volcano called Eyjafjallajökull spread from Iceland and caused widespread disruption of air travel across Europe.
Here are 10 facts about volcanoes…
The vast cloud of volcanic ash from Iceland (the large grey streak near the top of the image) sweeping down towards Ireland (bottom right) and the UK on 15 April. Source: European Space Agency
- A volcano is an opening or rupture in a planet’s surface or crust. This allows hot liquid rock, ash and gases to escape from below the surface.
- The word “volcano” comes from the name of Vulcano island off Sicily, which in turn was named after Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology (sometimes spelt “vulcanology”).
- The Earth’s crust is made up of huge slabs called tectonic plates, which fit together like a messy jigsaw puzzle. Volcanoes tend to occur near the edges of them when the plates move apart or come together – earthquakes occur when the plates slide over each other.
- The liquid rock inside a volcano is called magma. When it flows out of the volcano, at temperatures from 700° to 1,200°C, it’s called lava. As the lava and ash accumulate, they can build up to form mountains.
- Sometimes rapidly cooling lava turns into basalt. One of the most famous basalt flows in the world is the Giant’s Causeway in Northern Ireland.
- Another volcanic rock formation is pumice - the only rock that can float in water. It is usually grey and full of bubbly holes. Pumice is widely used in construction and to make stone-washed jeans. You might also find pumice in your bathroom – it’s also used in cosmetic exfoliants and some toothpastes.
- Earth has at least 1,500 active volcanoes, and Iceland has about 130 volcanic mountains, of which 18 have erupted since its settlement around 900 AD.
- Scientists consider a volcano to be extinct if it is unlikely to erupt again, because it no longer has a lava supply.
- The ash that volcanoes throw into the air can present a hazard to jet aircraft, because their high operating temperatures can melt the particles. The plumes from Eyjafjallajökull can be seen as far away as the International Space Station.
- The ocean floor has many active submarine volcanoes, and other planets and moons have volcanoes too. For example cryovolcanoes (ice volcanoes) have been found on some moons of Jupiter, Saturn and Neptune. Instead of molten rock, these ice volcanoes erupt substances such as water, ammonia or methane.
Learn more
Read how NASA is using automated satellites and artificial software to follow Iceland’s volcano – and how an Irish scientist pioneered the study of volcanoes over a century ago.
