Everything you need to know about volcanoes

There are 1,500 volcanoes recorded as active in the world. Nobody knows how many are inactive.

The largest active one is Mauna Loa, in Hawaii. It has a volume of about 40,000 cu km. The area above sea level occupies 5,125 sq km. The most active volcano is Kilauea, also in Hawaii, which has been in near- continuous eruption since 1983.

Most of the earth's volcanoes are located around the Pacific Ocean because that is where most of the Earth's subduction zones are found. A subduction zone is a place where one "plate" of the earth's crust is pushed under another plate. The lower plate eventually starts to melt, and the material rises up through the upper plate, forming a mountain chain of volcanoes, such as the Andes, or a chain of volcanic islands such as the Marianas or Aleutians.

When hot rocks, called magma, and gases break through the planet's crust, an eruption occurs. The buildup of ash and lava flows around the eruption hole (or vent) makes a volcano. Some erupt for only a few days or weeks and never do so again. Large volcanoes can erupt many thousands of times over millions of years.

Lava is not the only threat from volcanoes. Mammoth Mountain in eastern California is currently emitting dangerous levels of carbon dioxide, which has forced the US Forest Service to close a nearby campsite because it could kill people. Trees are being killed by the emissions. Tsunami - tidal waves - can kill people on shorelines near erupting undersea volcanoes.

The last volcano was active in the UK about 50 million years ago, during the Tertiary period, when volcanic activity affected northwest Scotland and north Wales. Since Britain is now far away from any subduction zone, it is unlikely to have any volcanic activity for millions of years.

The temperature of a volcano depends on its activity. Most volcanoes are inactive most of the time, and thus are no warmer than non-volcanic mountains. The most common type of lava, basalts, usually have eruption temperatures of about 1150o-1200oC.

The youngest volcano is usually considered to be Paricutin in Mexico, which grew out of a corn field in 1943 and erupted for almost nine years.

The average abount of material thrown out of an erupting volcano is estimated to be about 10 million cubic metres.

The Volcanic Explosivity Index (VEI), in use since 1982, grades eruptions from 0 (gentle) to 8 (cataclysmic). The biggest eruption in recorded history was from the Tambora volcano in Indonesia in 1815 (VEI 7). The explosion produced 40 cu km of ash and killed 10,000 people. Another 80,000 died from the ensuing famine. There has been no VEI 8 eruption for 10,000 years.

About 70,000 people have died since 1902 through eruptions and their related impacts, such as tsunami, starvation, avalanches and disease in evacuation camps.

Mount Pinatubo, which erupted in the Philippines in 1991, is thought to have cooled world temperatures by an average of 0.5oC over three years because dust it threw up reflected some of the sun's light.

Suggested Topics
Start your day with The Independent, sign up for daily news emails
PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
ebooks
ebooksA year of political gossip, levity and intrigue from the sharpest pen in Westminster
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Account Manager

£20000 - £35000 per annum: Recruitment Genius: This full service social media ...

Recruitment Genius: Data Analyst - Online Marketing

£24000 - £35000 per annum: Recruitment Genius: We are 'Changemakers in retail'...

Austen Lloyd: Senior Residential Conveyancer

Very Competitive: Austen Lloyd: Senior Conveyancer - South West We are see...

Austen Lloyd: Residential / Commercial Property Solicitor

Excellent Salary: Austen Lloyd: DORSET MARKET TOWN - SENIOR PROPERTY SOLICITOR...

Day In a Page

Isis in Iraq: Yazidi girls killing themselves to escape rape and imprisonment by militants

'Jilan killed herself in the bathroom. She cut her wrists and hanged herself'

Yazidi girls killing themselves to escape rape and imprisonment
Ed Balls interview: 'If I think about the deficit when I'm playing the piano, it all goes wrong'

Ed Balls interview

'If I think about the deficit when I'm playing the piano, it all goes wrong'
He's behind you, dude!

US stars in UK panto

From David Hasselhoff to Jerry Hall
Grace Dent's Christmas Quiz: What are you – a festive curmudgeon or top of the tree?

Grace Dent's Christmas Quiz

What are you – a festive curmudgeon or top of the tree?
Nasa planning to build cloud cities in airships above Venus

Nasa planning to build cloud cities in airships above Venus

Planet’s surface is inhospitable to humans but 30 miles above it is almost perfect
Surrounded by high-rise flats is a little house filled with Lebanon’s history - clocks, rifles, frogmen’s uniforms and colonial helmets

Clocks, rifles, swords, frogmen’s uniforms

Surrounded by high-rise flats is a little house filled with Lebanon’s history
Return to Gaza: Four months on, the wounds left by Israel's bombardment have not yet healed

Four months after the bombardment, Gaza’s wounds are yet to heal

Kim Sengupta is reunited with a man whose plight mirrors the suffering of the Palestinian people
Gastric surgery: Is it really the answer to the UK's obesity epidemic?

Is gastric surgery really the answer to the UK's obesity epidemic?

Critics argue that it’s crazy to operate on healthy people just to stop them eating
Homeless Veterans appeal: Christmas charity auction Part 2 - now LIVE

Homeless Veterans appeal: Christmas charity auction

Bid on original art, or trips of a lifetime to Africa or the 'Corrie' set, and help Homeless Veterans
Pantomime rings the changes to welcome autistic theatre-goers

Autism-friendly theatre

Pantomime leads the pack in quest to welcome all
The week Hollywood got scared and had to grow up a bit

The week Hollywood got scared and had to grow up a bit

Sony suffered a chorus of disapproval after it withdrew 'The Interview', but it's not too late for it to take a stand, says Joan Smith
From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?

Panto dames: before and after

From Widow Twankey to Mother Goose, how do the men who play panto dames get themselves ready for the performance of a lifetime?
Thirties murder mystery novel is surprise runaway Christmas hit

Thirties murder mystery novel is surprise runaway Christmas hit

Booksellers say readers are turning away from dark modern thrillers and back to the golden age of crime writing
Anne-Marie Huby: 'Charities deserve the best,' says founder of JustGiving

Anne-Marie Huby: 'Charities deserve the best'

Ten million of us have used the JustGiving website to donate to good causes. Its co-founder says that being dynamic is as important as being kind
The botanist who hunts for giant trees at Kew Gardens

The man who hunts giants

A Kew Gardens botanist has found 25 new large tree species - and he's sure there are more out there