ROAR OFTHE SORCERESS THE

Remember the Icelandic ash cloud volcano? Read about the far bigger one due to erupt any moment — and brace yourself for the . . .

Avolcanic explosion so colossal it unleashes gouts of toxic ash into the atmosphere capable of poisoning more than 200,000 people to death. Europe’s temperatures plummeting for years, crop failures, mass hypothermia, transport chaos as Europe’s commercial flights are grounded for weeks, if not months. Swathes of land flooded by melted ice, farmland poisoned and villages wiped out.

a hyperbolic doomsday scenario? no, say scientists. it’s all too real a prospect.

Because deep beneath a glacier in iceland, a cataclysmic giant is stirring. Known in local lore as the ‘evil sorceress’, she is gearing up to unleash her deadly wrath on the whole of northern Europe, according to experts.

They fear that if the Katla volcano erupts, its devastating effects would dwarf those of its near neighbour Eyjafjallajokull, which exploded in 2010, releasing an ash cloud that led to the cancellation of more than 100,000 flights. it was the largest commercial airtraffic shutdown since World War ii as millions were stranded across northern Europe between mid-april and mid-May.

These cataclysmic predictions are based on a similar eruption from the laki volcanic system, 30 miles north-west of Katla, in 1783.

That explosion killed a fifth of iceland’s population and created an ash cloud that obscured the sun’s rays across the northern Hemisphere for months, sending temperatures plummeting by 3c.

Prevailing winds brought millions of tonnes of lethal sulphur dioxide and sulphuric acid swirling almost 1,000 miles across the ocean to land on Britain. in the UK, an estimated 23,000 people died from poisoning and extreme cold. local newspapers reported how poisonous ash precipitated fog so thick that boats stayed in port, unable to navigate, and the sun was ‘coloured like it has been soaked in blood’.

The Hertfordshire poet William cowper wrote of farmers struggling to gather harvests: ‘The labourers having been almost every day carried out of the field incapable of work and many die.’

all told, it was one of the greatest natural disasters to befall our country in the past 300 years.

The last time Katla erupted was 100 years ago, when it threw five times more ash into the sky than Eyjafjallajokull did in 2010 — so much that it extended iceland’s south coast by three miles.

The glacial melt also unleashed a torrent of water, mud and icebergs that was claimed to be similar in volume to the amazon river. astonishingly, no one was killed, one spot of comfort when we’re considering the disaster that could be on its way shortly.

one of the worries is that this geological timebomb is long overdue. Historical records show that Katla erupts once every 60 years on average, and has now been dormant for a century.

To put the length of Katla’s current slumber into context, it’s the longest the volcano has gone without erupting since the vikings settled in iceland at the end of the ninth century.

So why are we worrying about this now? Because local monitoring experts warn that it is displaying ominous activity, pouring carbon dioxide gas into the atmosphere on a huge scale, a classic precursor to eruption because it signals the build up of magma within the volcano.

Deep underground the rumblings have already begun.

last July, a flood of water burst from the ice on top of Katla, washing away a bridge.

This indicated that a powerful pulse of heat had struck the base of the 3,000ft-thick Myrdalsjokull glacier that sits on top of the volcano’s crater. Since then, scientific monitoring equipment has shown erratic geological movements and strong bursts of earthquake activity.

all point to the fact that, deep beneath the ground, massive flows of molten rock are indeed growing stronger. and, right now, we are approaching the most perilous period of the year.

in iceland, autumn is the peak time for earthquake activity — and along with it the highest risk of eruptions. The build up of power inside Katla is massively intensified by the presence of the glacier on its crater, which acts much like the lid on a giant pressure cooker.

as a result, when the volcano erupts scientists say it will eject a much larger ash plume than Eyjafjallajokull — even if the eruption’s actual strength is only comparatively small.

This is because high-pressure explosions cause the ejected magma to break up into very fine ash particles, so light in weight that they create vast toxic clouds that can remain airborne for weeks or months.

This is the major problem for aeroplanes. When it is sucked into a jet engine, ash is initially heated to a temperature so high that it turns into molten glass. When the molten glass reaches the back of the engine, it cools and solidifies on the turbine blades, jamming the engine and causing the plane to plunge from the sky.

Yet despite having recently witnessed at first hand the destruction and misery wrought by Eyjafjallajokull, it is Katla that the people of iceland fear most.

Her legend stretches back more than eight centuries, and the story goes that the original Katla was an ill- tempered and cruel housekeeper in the employ of a local monastery, where even the abbot was terrified of her supernatural powers.

one day, a young shepherd boy made the fatal mistake of disobeying her. in a rage, she drowned him in a vat of acid and it took months for the boy’s sad remains to be discovered.

When this ‘evil sorceress’ was summoned to face justice, she ran away, helped by a pair of magical breeches that enabled her to run far and fast without feeling tired.

Upon reaching the top of the mountain she plunged herself into the Myrdalsjokull glacier, which caused it to erupt, destroying the monastery and all its inhabitants.

The legend warns that one day Katla will return — to wreak further vengeance.

Such fear is anything but mythical for those who live in the volcano’s shadow.

it ought to be a worry, too, for the many sightseers and hikers who typically travel to the area to walk on the glacier or to marvel at the surrounding plains, one of iceland’s main tourist attractions.

last year, safety authorities warned that people may have as little as 15 minutes to escape to safety when an eruption comes.

But even that may not be enough. The authorities plan to send emergency text messages to all mobile phones in the affected area if an eruption is imminent, telling residents and travellers to evacuate or move to safety.

However, a practice drill last year found that mobile reception is sparse and that many travellers near the glacier would never receive the message. They would surely be among Katla’s first victims, caught in the tsunami of melted glacial ice roaring down the sides of the volcano.

ever-present peril does not seem to worry all the locals, however. in the village of vik, which sits in the shadow of Katla’s 5,000ft peak, the hotel manager Palmi Kristjansson is actually looking forward to seeing it erupt.

‘i’ve heard people talk about Katla erupting all my life. it will be big… i would like to see it.

‘i want to live it,’ he told reporters last year. ‘i know that’s a stupid thing to say because many people will experience damage. But it’s just normal life for us. We don’t worry.’

Such fatalism is admirable when faced with a titanic force of nature. after all, what can anyone do to assuage Katla’s fury — other than try to find travel insurance that covers volcanic disruption?

We have no choice but to hope that, after a whole century of snoozing, the evil icelandic sorceress decides merely to rouse briefly, belch gently — and then turn over for another century of peaceful slumber.

Whether that will be enough to satisfy her, we can only wait and see.