How Krakatoa made the biggest bang

When the Krakatoa volcano erupted in 1883, it unleashed one of the most violent explosions mankind had ever seen. Ahead of a lavish new BBC drama, Sanjida O'Connell examines how the impact was felt around the world

It was 6am on August 26 in 1883, when the volcano on Krakatoa, a small island in Indonesia, catastrophically erupted. This earth-shattering event became the greatest natural disaster of the 19th century: the sky was bathed in an unearthly red glow and the fallout was felt around the world.

The force of the eruption created the loudest noise ever recorded: it was heard 4,653km away on Rodriguez Island in the Indian Ocean and some 4,800km away in Alice Springs; shock waves travelled around the world seven times; and the force of the blast was some 10,000 times greater than that of the hydrogen bomb dropped on Hiroshima. The volcano left 36,000 people dead and the survivors battled to cope with tsunamis, further eruptions and superheated ash clouds.

As the volcano erupted, a plume of ash swept 80km into the sky, the hot gas became unstable and raced across nearby islands at 150km. "Those who weren't killed by the intense heat," says Dr Dave Rothery, from the Department of Earth Sciences at the Open University, "would have been sandblasted to death. It was hot enough to carbonise everything in its path."

The real killers, though, were the giant tsunamis that were unleashed, reaching heights of 40m and which were so violent that they flung sections of coral reef ashore, some weighing as much as 600 tons. Like the Indonesian tsunami on Boxing Day 2004, these tsunamis destroyed everything in their path.

This Sunday, the BBC re-examines the impact of one of the world's largest volcanoes in a factual drama, Krakatoa - The Last Days, and in an accompanying documentary, Krakatoa Revealed. Human tragedy aside, Krakatoa was important because it was declared a "modern" disaster and became one of the first global media events.

It produced a wealth of first-hand survivor accounts: a German quarry manager recounted being hurled by a wall of water from the top of his office block and swept into the jungle below. To his astonishment, he saw a crocodile being carried alongside him and incredibly he leapt on the animal's back and rode it for 3km before being deposited, unharmed, on the rainforest floor.

The rest of the world heard such stories almost instantly because a series of underwater telegraph cables had been recently laid traversing the globe. For the first time, operators were able to communicate stories to their counterparts across the globe using morse code. As Professor Nick Petford, from the School of Earth Sciences and Geology at Kingston University, London, and presenter of the BBC documentary explains, "This is the first time a volcano had exploded and was known about instantly. The underwater telegraph cables were a network for communication, the precursor to the internet."

In these days of instant global access, it's easy to forget how revolutionary this was: Krakatoa has been erupting irregularly since 250 AD; the last previous explosion was even more powerful and had happened only 200 years before the one in 1883, yet few had heard of this catastrophe.

This new technology meant that Krakatoa also generated the first modern scientific study of a volcanic eruption. "At the time geology was a lively academic discipline," says Petford. "A Dutch scientist, Rogier Verbeek, got there very quickly and recorded everything and his report was an astoundingly inspired piece of work."

Verbeek was quickly followed by a team of geologists from London's Royal Society and what was immediately obvious was that while two-thirds of the island of Krakatoa had been destroyed, a string of new islands had formed where the sea had been 36m deep. Many were ephemeral but Anak Krakatoa (child of Krakatoa), which formed in the remnants of its parent, was here to stay: it's been erupting since 1927 and the last recorded explosion was in 2001.

So what made Krakatoa explode so powerfully? Indonesia has many active volcanoes (132 have exploded in the past 10,000 years) because the islands lie above two tectonic plates, one of which is being pulled underneath the other at a rate of 6cm per year. Originally Verbeek thought that Krakatoa was so fierce because sea water flooded into the volcano, reacting with molten lava; the build-up of pressure from the resulting steam would have led to an enormous blast.

Petford has an alternative theory. He uses computer models combined with sandcastles - volcanoes made of sand - into which he pumps air to mimic the build up of pressure from gas deep within the volcano. His model of Krakatoa showed that gas pressure leads to "massive sector collapse": a large portion of the volcano collapses under the internal pressure. His model left a crater and landslide scar very like the remains of Krakatoa.

"Our best idea about what happened is that the final stage of the Krakatoa eruption was marked by a massive internal failure," says Petford, "perhaps due to a landslide that exposed lots of magma to atmospheric pressure."

The best way of predicting a blast is to record seismic activity within a volcano. Small earthquakes indicate that the volcano is becoming unstable. However, many countries do not have the money to monitor volcanic activity. Conversely, volcanoes in wealthy areas are also a problem. "Look at Mount Vesuvius," says Petford, "It erupted in the Second World War and it will erupt again. But people have built houses further and further up the slopes. You have a penthouse view across the Bay of Naples, your house cost a fortune, would you abandon it?"

Mount Vesuvius is not the only slumbering supervolcano. Krakatoa, or rather, its child, is also bubbling away. Professor Richard Fiske, from America's Smithsonian Institute, and one of the authors of a scientific book on Krakatoa, says, "It's not going to erupt in our lifetime." But given Krakatoa's history, it seems highly likely that it could explode in our children's.

Krakatoa - The Last Days, a factual drama, BBC1, Sunday 7 May, 8-9.30pm; Krakatoa Revealed, BBC1, Sunday 7 May, 10-10.50pm

Angry mountains: the power of nature

As you read this, 20 volcanoes are erupting throughout the world. In the past 10,000 years 1,300 have erupted and estimates suggest that there have been more than a million underwater explosions. These are five of the worst explosions that humankind has recorded.

Montserrat

In 1902 Mount Pelée on the French Island of Martinique, 150 miles south of Montserrat erupted, killing 28,000 people in a pyroclastic flow. This is a mixture of hot lava turned into a fluid by expanding volcanic gas and air, which is hot enough to melt glass and flows at speeds of around 150km. Volcanic activity has now moved to Montserrat, which has been active since 1995 and may be in danger of erupting at any point.

Mount St Helen's

On Sunday morning, May 18, 1980, Mount St Helen's in Washington State, erupted. The north face of the mountain collapsed, causing a massive rock avalanche. Almost 230 square miles of forest was blown down or buried beneath ash deposits. A column of ash rose hundreds of metres into the air and the eruption lasted for nine hours. Around 24,000 animals and 56 people died.

Tambora

The explosion in 1815 of the Indonesian Tambora volcano was the largest recorded. About 150 cubic kilometres of ash (150 times more than was produced when Mount St Helens erupted) was blown 44km into the sky and spread for 1,300km. Around 92,000 people were killed.

Toba

Toba, in Sumatra, exploded 74,000 years ago. The blast was so strong that a mixture of ash and sulphur dioxide was thrown into the stratosphere, blocking out the sun's rays and causing the temperature to plummet. Some scientists believe that it almost led to the extinction of humanity as only a few thousand people survived.

Vesuvius

Vesuvius has exploded a number of times in the past 17,000 years; the most famous eruption was on 24 August 79AD when a pyroclastic flow destroyed the Roman cities of Pompeii and Herculaneum, burying thousands beneath the lava and preserving their bodies.

Start your day with The Independent, sign up for daily news emails
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: Purchase Ledger Administrator

£5120 per annum: Recruitment Genius: You will be working for one of the countr...

Recruitment Genius: Engineering Surveyor

£20000 - £23000 per annum: Recruitment Genius: An opportunity has arisen for a...

Recruitment Genius: Customer Services Support

£9000 per annum: Recruitment Genius: You will be working for one of the countr...

Recruitment Genius: Junior Estimator

£17000 - £18000 per annum: Recruitment Genius: An opportunity has arisen for a...

Day In a Page

Not even the 'putrid throat' could stop the Ross Poldark swoon-fest'

Not even the 'putrid throat' could stop the Ross Poldark swoon-fest'

How a costume drama became a Sunday night staple
Miliband promises no stamp duty for first-time buyers as he pushes Tories on housing

Miliband promises no stamp duty for first-time buyers

Labour leader pushes Tories on housing
Aviation history is littered with grand failures - from the the Bristol Brabazon to Concorde - but what went wrong with the SuperJumbo?

Aviation history is littered with grand failures

But what went wrong with the SuperJumbo?
Fear of Putin, Islamists and immigration is giving rise to a new generation of Soviet-style 'iron curtains' right across Europe

Fortress Europe?

Fear of Putin, Islamists and immigration is giving rise to a new generation of 'iron curtains'
Never mind what you're wearing, it's what you're reclining on

Never mind what you're wearing

It's what you're reclining on that matters
General Election 2015: Chuka Umunna on the benefits of immigration, humility – and his leader Ed Miliband

Chuka Umunna: A virus of racism runs through Ukip

The shadow business secretary on the benefits of immigration, humility – and his leader Ed Miliband
Yemen crisis: This exotic war will soon become Europe's problem

Yemen's exotic war will soon affect Europe

Terrorism and boatloads of desperate migrants will be the outcome of the Saudi air campaign, says Patrick Cockburn
Marginal Streets project aims to document voters in the run-up to the General Election

Marginal Streets project documents voters

Independent photographers Joseph Fox and Orlando Gili are uploading two portraits of constituents to their website for each day of the campaign
Game of Thrones: Visit the real-life kingdom of Westeros to see where violent history ends and telly tourism begins

The real-life kingdom of Westeros

Is there something a little uncomfortable about Game of Thrones shooting in Northern Ireland?
How to survive a social-media mauling, by the tough women of Twitter

How to survive a Twitter mauling

Mary Beard, Caroline Criado-Perez, Louise Mensch, Bunny La Roche and Courtney Barrasford reveal how to trounce the trolls
Gallipoli centenary: At dawn, the young remember the young who perished in one of the First World War's bloodiest battles

At dawn, the young remember the young

A century ago, soldiers of the Empire – many no more than boys – spilt on to Gallipoli’s beaches. On this 100th Anzac Day, there are personal, poetic tributes to their sacrifice
Dissent is slowly building against the billions spent on presidential campaigns – even among politicians themselves

Follow the money as never before

Dissent is slowly building against the billions spent on presidential campaigns – even among politicians themselves, reports Rupert Cornwell
Samuel West interview: The actor and director on austerity, unionisation, and not mentioning his famous parents

Samuel West interview

The actor and director on austerity, unionisation, and not mentioning his famous parents
General Election 2015: Imagine if the leading political parties were fashion labels

Imagine if the leading political parties were fashion labels

Fashion editor, Alexander Fury, on what the leaders' appearances tell us about them
Phumzile Mlambo-Ngcuka: Home can be the unsafest place for women

Phumzile Mlambo-Ngcuka: Home can be the unsafest place for women

The architect of the HeForShe movement and head of UN Women on the world's failure to combat domestic violence