Towering above a remote Pacific island, the volcano is some 8,000 miles from Britain — but nowhere is safe from the devastation it will unleash on the world.

For days, explosions like distant cannon fire have terrified locals and now it’s about to blow with a force 50,000 times greater than that of the atomic bomb dropped on Hiroshima.

As the molten rock finally punches through the surface, giant flames shoot up into the sky with a blast that can be heard 1,200 miles away and sends a red-hot river of lava flowing down the volcano’s slopes. Along with choking noxious gases, this incinerates or asphyxiates many tens of thousands of islanders and destroys the homes of countless more.

Elsewhere, the giant ash cloud spewed into the atmosphere sees freak weather conditions as far afield as Western Europe. Aeroplanes are grounded, harvests are destroyed and famine and disease kill millions of people.

The Vesuvius eruption in 79AD saw the town of Pompeii destroyed within hours of the explosion

Victims were covered in ash as they tried to escape the doomed port city 

They include many in Britain where crematoriums are overwhelmed by the bodies piling up in mass morgues and protests against soaring food prices turn to violent riots.

No, this is not the plot of a Hollywood disaster movie, but rather a scenario based on previous eruptions and one that has a one-in-six chance of happening this century, according to an article published in the latest issue of the respected science journal Nature.

The grim prediction comes from Dr Mike Cassidy, a volcanologist from the University of Birmingham, and Dr Lara Mani, from Cambridge University’s Centre for the Study of Existential Risk.

It’s based on deposits of sulphur — a main component of volcanic gases — found in ancient ice deposits in Antarctica and Greenland. These indicate how frequently major eruptions have happened in the past and so how likely they are in the future, and challenge what they call the ‘broad misconception’ that the risks of a major eruption are low.

Terrifyingly, those odds — equivalent to the roll of a dice — relate to an eruption rating of at least seven on the Volcanic Explosivity Index (VEI), a measure which is equivalent to the Richter scale for earthquakes and runs from one for the smallest to eight for the most powerful.

To put that in perspective, the eruption of Mount Vesuvius, which claimed the lives of around 16,000 people in Pompeii and other Italian cities in 79AD, rated five on the VEI.

How such a cataclysmic event might unfold can be gauged from two historical VEI level seven eruptions. Both happened in Indonesia but had terrible ramifications in the rest of the world, Britain included.

Mount Pelée — Martinique, 1902 was the worst volcanic event of the 20th century. As the 4,500ft mountain began to erupt, insects and snakes disturbed by it surged down the mountain, attacking those in their path. In total, 30,000 perished

The first was in 1257 on the island of Lombok. The only eyewitness accounts, contained in a document written on palm leaves, describe how ‘Mount Samalas collapsed, followed by large flows of debris accompanied by the noise coming from boulders.

‘All houses were destroyed and swept away, floating on the sea, and many people died.’

A cloud of some 36 cubic miles of ash, pumice and other rock is thought to have circumnavigated the globe within a few weeks, filling the stratosphere with sulphuric acid particles that blocked out sunlight.

At his abbey in St Albans, Hertfordshire, English monk Matthew Paris recorded that the year 1258 began with ‘such unendurable cold, that it bound up the face of the earth, sorely afflicted the poor, suspended all cultivation and killed the young of the cattle’. And that was just the start.

That summer, he wrote that ‘owing to the scarcity of wheat, a very large number of poor people died; and dead bodies were found in all directions, swollen and livid, lying by fives and sixes in pigsties, on dunghills, and in the muddy streets’.

This eruption is said to have kick-started the Little Ice Age, a centuries-long chill which began at around this time and caused such phenomena as the freezing over of the River Thames.

Krakatoa — Sunda Strait, 1883: This small, uninhabited island east of Sumatra and west of Java saw an explosion which sent five cubic miles of earth 50 miles into the air. It destroyed the island and created a tsunami with 120ft waves as well as hurricanes. The eruption was heard in over 50 countries and at least 36,400 deaths are attributed to its effects

That ended in the mid-19th century, shortly after the world had suffered another VEI level seven eruption — that of Mount Tambora in April 1815. Only 100 miles from Samalas, it was every bit as deadly, killing around 100,000 people in its immediate aftermath before wreaking havoc further afield.

In 1816, Europe experienced what became known as ‘the year without a summer’.

During that seemingly endless winter, global temperatures dropped by an average of one degree and the blotting out of solar rays led to wild rumours that the sun was dying.

The frequent thunderstorms and constant rain kept people indoors for days at a time, inspiring English author Mary Shelley, holidaying in an equally gloomy Switzerland, to dream up the story of Frankenstein.

That begins with polar explorer Robert Walton, the man to whom the monster’s creator Victor Frankenstein tells his story, yearning for the North Pole, ‘a region of beauty and delight where… the sun is forever visible’.

In England, the decimation of the wheat harvest and subsequent rise in prices saw riots break out in various parts of East Anglia, where protesters armed themselves with wooden clubs studded with spikes and carried flags demanding ‘Bread or Blood’. Destroying threshing machines, they also torched barns and grain sheds and the protests ended only when they were threatened with the death penalty.

The cold and damp, combined with people moving from place to place as they begged for food, also sparked one of the worst typhus epidemics in history, killing 65,000 people as it spread out of Ireland and into Britain.

As if these lessons from history are not horrifying enough, the consequences could be even greater today with eight times the world population and more than 40 times the trade. ‘Our complex global networks could make us even more vulnerable to the shocks of a major eruption,’ says Mike Cassidy.

Just how vulnerable became clear with the VEI level four eruption of Iceland’s Eyjafjallajokull volcano in the spring of 2010. The closure of international airspace caused by the resulting ash cloud cost the world economy an estimated £4 billion.

Earlier this year, an undersea VEI level six volcano blew near the Tongan archipelago in the South Pacific ocean. Producing a vertical plume extending 30 miles above the Earth’s surface, and volcanic ash falling over hundreds of miles, it caused damage equivalent to almost one-fifth of Tonga’s gross domestic product.

Underwater cables were severed, cutting off Tonga’s communications with the outside world, and the blast created an atmospheric shockwave that travelled at close to the speed of sound, creating tsunamis that reached the coasts of South America and Japan, thousands of miles away. Fortunately the eruption, which killed three people, lasted only 11 hours, but the Nature article describes it as ‘the volcanic equivalent of a “near miss” asteroid whizzing by the Earth’.

‘Had it gone on for longer… it would have had repercussions for supply chains, climate and food resources worldwide,’ it added.

Other research has suggested that likely hotspots for future VEI level seven eruptions include the Taupo Volcano in the centre of New Zealand’s North Island and Iran’s Mount Damavand, which lies just 30 miles from the densely populated capital Tehran. But it may not be the known volcanoes that we have to worry about.

The sulphur deposits found in Antarctica and Greenland suggest that there have been 97 large-magnitude explosions in the last 60,000 years, yet we have established the whereabouts of only a handful and the undiscovered ones may well be ready to blow again.

‘Volcanoes can lie dormant for a long time, but still be capable of sudden and extraordinary destruction,’ explains Dr Cassidy.

Apart from identifying and monitoring volcanoes, he and Lara Mani are calling for research into ways of reducing the impact they have. Short-lived warming agents, such as hydrofluorocarbon, might be used to counteract the sunlight-blocking sulphuric acid particles in the atmosphere, or they could be removed by substances sprayed from high-altitude aeroplanes.

Nevado del Ruiz — Colombia, 1985 After a small first eruption which was ignored, the volcano blew again, melting a glacier which released 43 million tonnes of water mixed with ash, rocks and trees. Half an hour later the town of Armero was subsumed. More than 20,000 of its 29,000 inhabitants died

Other possibilities include manipulating pockets of magma beneath active volcanoes to make them less explosive.

Such work is urgently needed, with Dr Mani comparing the impact of a giant volcanic event to that of a 1km-wide asteroid hitting the Earth.

‘They would have similar climatic consequences, but the likelihood of a volcanic catastrophe is hundreds of times higher than the combined chances of an asteroid or comet collision,’ she says.

She adds that while Nasa pumps hundreds of millions of dollars into asteroid threats annually, ‘there is a severe lack of global financing and coordination for volcano preparedness’.

‘This urgently needs to change. We are completely underestimating the risk to our societies that volcanoes pose and the current underinvestment in responding to this risk is simply reckless.’

It’s a dire warning — and one we ignore at our peril.