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.

Volcanoes are formed when molten rock escapes between two tectonic plates that are either moving apart or coming together. The molten rock rises from a magma chamber, up through a vent and erupts from the cone, sometimes violently. Over several thousand years the build up of rock can grow a volcano to the size of a mountain.

The liquid rock that forms a volcano is called either magma or lava. Magma is the liquid rock found inside a volcano and can range in temperature from 700 to 1,300 degrees Celsius, while it is called lava once it has erupted from the volcano. A vast number of chemicals make up this liquid rock, including silicon, magnesium, iron, titanium, sodium, potassium, phosphorous, hydrogen and sulphur.

Eruptions

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 50 kilometres. According to the Index, mega-colossal eruptions, only happen every 10,000 years or so.

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

Ultimately, 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 two millennia. No wonder it’s known as the "Lighthouse of the Mediterranean".

One of the phenomena of volcanic eruptions is the presence of lightning during an explosion where hot particles spewing from the volcano crash into each other and generate static electricity in the atmosphere.

Volcanoes Around The World

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.

The world’s most active volcano is located in a hotspot in the very centre of The Ring of Fire. Kilauea, in Hawaii, has been in a state of almost continuous eruption since 1983. Its name means "much spreading".

Mauna Loa, meaning "Long Mountain", is 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.

However, not all volcanoes are located on the surface of the Earth.

Submarine volcanoes are underwater fissures in the earth’s surface from which magma can erupt. They are estimated to account for 75% of annual magma output. 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.

Death and Destruction

Throughout the history of the world, thousands if not millions of people have lost their lives to volcanic eruptions. Today, more than one tenth of the world’s population live within what’s known as the "danger range" of an active volcano.

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".

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

Solar System

Heading away from our planet, there are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth. Olympus Mons is the biggest of Mars' shield volcanoes and is also our Solar System's second tallest mountain.

Jupiter’s moon is the most volcanically active object in the solar system. It is covered with volcanoes that erupt sulphur, sulphur dioxide and silicate rock, and is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1,500 degrees Celsius.

Probably better to stick with the volcanoes we have here, despite their danger.

Quick Facts

• Magma can reach 1,300 degrees Celsius.
  
• The Italian volcano Stromboli has erupted for the last 2,000 years.
  
• Mega-colossal volcano plume heights can reach in excess of 50 km.
• Submarine volcanoes account for 75% of the Earth's annual magma output.
  
• Olympus Mons is the tallest volcano in the Solar System.