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Volcanos

They're capable of causing tsunamis, wiping out entire populations and sending global temperatures into chaos. Volcanos are one of nature's deadliest attributes. Get the lowdown on these explosive hotspots...

Mauna Loa (meaning 'Long Mountain') is believed to be the largest volcano in the world. Situated about four kilometres above sea level, it covers half the island of Hawaii and, from its base to its summit, is taller than Mount Everest. It has erupted over 30 times in the last 150 years; the last major eruption was in 1984.

The word 'volcano' comes from the Italian island of Vulcano, meaning 'burning mountain'. Etymologists also suggest the word may have derived from Vulcan, the Roman God of fire and metalworking.

Throughout history thousands have lost their lives to volcanos. The biggest death toll - 70,000 - came as a result of the Indonesian Tambora in 1815. The explosion jettisoned such a large amount of ash it caused a global drop in temperatures; some historians call 1815 the 'year without a summer'. As well as those killed in the initial explosion, many lost their lives to resulting disease and water contamination.

There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth. Jupiter's moon Io is the most volcanically active object in the solar system. It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1,500 degrees Celsius.

The world's most active volcano is in Hawaii. Kilauea, meaning 'much spreading', has been in a state of almost continuous eruption since 1983. Piton de La Fournaise ('Peak of the Furnace') in the Indian Ocean is also highly active. Its last major eruption began in August 2006 and ended on New Year's Day 2007.

When a volcano erupts, the surroundings can get pretty darn warm. Basalt lava (the most common type) can reach temperatures of 1150-1200 degrees Celsius, while rocks around the volcano can also reach temperatures of up to 1,000 degrees Celcius.

Submarine volcanoes are underwater fissures in the earth's surface from which magma can erupt. They estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as mid-ocean ridges. Although most are located in the depths of oceans, some also exist in shallow water, which can spew material into the air during an eruption.

Volcano experts measure eruptions on the Volcanic Explosivity Index. This index ranges from zero to eight, zero being a non-explosive volcano (like Kilauea in Hawaii), eight being a mega-colossal volcano, with plume heights in excess of 25 metres. According to the Index, mega-colossal eruptions, thankfully, only happen every 10,000 years or so.

It's almost impossible to predict how long a volcanic eruption will last. The Italian volcano Stromboli has been in a continuous state of eruption for more than 2,000 years. No wonder it's known as the 'Lighthouse of the Mediterranean'.

Vast arrays of chemicals and elements spill from an erupting volcano. These include silicon, magnesium, iron, titanium, sodium, potassium, phosphorous, hydrogen and sulphur.

What's the difference between magma and lava? Simple: magma is the liquid rock found inside a volcano, lava is what this liquid rock is called once it's erupted from the volcano. Magma ranges in temperature from 700 to 1,300 degrees Celsius.

The Ring of Fire, the name given to a cluster of volcanos encircling the basin of the Pacific Ocean, contains 700 of the world's most active volcanos. It also contains around 81% of the world's Earthquakes.

Humans aren't the only victims of volcanos. When Washington's Mouth St Helens erupted in 1980, it killed an estimated 24,000 creatures. It also destroyed over 230 square miles of forestry.

Your chances of witnessing an erupting volcano are higher than you might think. More than one tenth of the world's population live within what's known as the 'danger range' of an active volcano.

One of the phenomena of volcanic eruptions is the presence of lightning during an explosion. Experts cannot pinpoint exactly why this should happen, but many believe it's due to lots of hot particles crashing into each other and causing static electricity in the atmosphere.

When is it on?

Supervolcano is next on at 10.00pm on Thursday 30th October on Watch

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