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
Have you tried new the Independent Digital Edition apps?
ebooks
ebooksA special investigation by Andy McSmith
  • Get to the point
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: Project Implementation Executive

£18000 - £23000 per annum: Recruitment Genius: They work with major vehicle ma...

Recruitment Genius: Chiropractic Assistant

£16500 per annum: Recruitment Genius: A Chiropractic Assistant is needed in a ...

Recruitment Genius: Digital Account Executive - Midlands

£18000 - £26000 per annum: Recruitment Genius: They work with major vehicle ma...

Recruitment Genius: Web Developer

£28000 - £30000 per annum: Recruitment Genius: This company provides coaching ...

Day In a Page

NHS struggling to monitor the safety and efficacy of its services outsourced to private providers

Who's monitoring the outsourced NHS services?

A report finds that private firms are not being properly assessed for their quality of care
Zac Goldsmith: 'I'll trigger a by-election over Heathrow'

Zac Goldsmith: 'I'll trigger a by-election over Heathrow'

The Tory MP said he did not want to stand again unless his party's manifesto ruled out a third runway. But he's doing so. Watch this space
How do Greek voters feel about Syriza's backtracking on its anti-austerity pledge?

How do Greeks feel about Syriza?

Five voters from different backgrounds tell us what they expect from Syriza's charismatic leader Alexis Tsipras
From Iraq to Libya and Syria: The wars that come back to haunt us

The wars that come back to haunt us

David Cameron should not escape blame for his role in conflicts that are still raging, argues Patrick Cockburn
Sam Baker and Lauren Laverne: Too busy to surf? Head to The Pool

Too busy to surf? Head to The Pool

A new website is trying to declutter the internet to help busy women. Holly Williams meets the founders
Heston Blumenthal to cook up a spice odyssey for British astronaut manning the International Space Station

UK's Major Tum to blast off on a spice odyssey

Nothing but the best for British astronaut as chef Heston Blumenthal cooks up his rations
John Harrison's 'longitude' clock sets new record - 300 years on

‘Longitude’ clock sets new record - 300 years on

Greenwich horologists celebrate as it keeps to within a second of real time over a 100-day test
Fears in the US of being outgunned in the vital propaganda wars by Russia, China - and even Isis - have prompted a rethink on overseas broadcasters

Let the propaganda wars begin - again

'Accurate, objective, comprehensive': that was Voice of America's creed, but now its masters want it to promote US policy, reports Rupert Cornwell
Why Japan's incredible long-distance runners will never win the London Marathon

Japan's incredible long-distance runners

Every year, Japanese long-distance runners post some of the world's fastest times – yet, come next weekend, not a single elite competitor from the country will be at the London Marathon
Why does Tom Drury remain the greatest writer you've never heard of?

Tom Drury: The quiet American

His debut was considered one of the finest novels of the past 50 years, and he is every bit the equal of his contemporaries, Jonathan Franzen, Dave Eggers and David Foster Wallace
You should judge a person by how they peel a potato

You should judge a person by how they peel a potato

Dave Hax's domestic tips are reminiscent of George Orwell's tea routine. The world might need revolution, but we like to sweat the small stuff, says DJ Taylor
Beige is back: The drab car colours of the 1970s are proving popular again

Beige to the future

Flares and flounce are back on catwalks but a revival in ’70s car paintjobs was a stack-heeled step too far – until now
Bill Granger recipes: Our chef's dishes highlight the delicate essence of fresh cheeses

Bill Granger cooks with fresh cheeses

More delicate on the palate, milder, fresh cheeses can also be kinder to the waistline
Aston Villa vs Liverpool: 'This FA Cup run has been wonderful,' says veteran Shay Given

Shay Given: 'This FA Cup run has been wonderful'

The Villa keeper has been overlooked for a long time and has unhappy memories of the national stadium – but he is savouring his chance to play at Wembley
Timeless drama of Championship race in league of its own - Michael Calvin

Michael Calvin's Last Word

Timeless drama of Championship race in league of its own