A spectacular volcanic eruption beneath Iceland’s biggest glacier has spewed a column of ash and gas more than seven miles into the air, forcing airlines to divert flights to avoid the blast.

At least ten transatlantic flights have been rerouted south of Iceland to skirt the plume rising from the Grimsvötn volcano in the east of the island, which began to erupt on Monday and continues to steam with noxious fumes and debris.

The cloud of ash has already started to land in Norway, Sweden and Finland, though without causing any damage or putting human health at risk.

Meteorologists said it was fortunate that prevailing winds were carrying the column towards Scandinavia rather than to the south of Iceland, where they would have caused havoc in the air traffic trunk route for flights between Europe and North America.

A change in the wind taking the ash south or west could disrupt up to 50 flights a day, though this is not forecast. "I don’t even want to think about that," said Bergthor Bergthorsson of the Icelandic Aviation Authority.

Dozens of domestic flights to the north and east of Iceland have been grounded by of the ash, which can stop aircraft engines if they attempt to fly through it.

The Dutch airline KLM, which operates several flights across the Arctic, has also cancelled 59 flights, though fog at Amsterdam’s Schipol airport was also a factor.

The National Air Traffic Control Services (NATS), however, said that no flights to or from Britain had been affected, as their routes did not take them through ash-clogged airspace.

Flight plans are set 12 hours before departure to allow airlines to take advantage of prevailing weather conditions, and a NATS spokesman said it had been a simple matter to route them away from the area of maximum disruption.

The Grimsvötn volcano, which is buried under 650ft (200m) of ice beneath the Vatnajökull ice cap, last erupted in 1998, and while that event caused little damage, eruptions in 1995 and 1993 led to major flooding.

The surrounding region is largely uninhabited, however, and no evacuations have been ordered this time.

The volcano is a variety known as a caldera — a large, shallow crater above a "hot spot" of magma (molten rock). The world’s most celebrated caldera is Yellowstone National Park in the United States, most of which is effectively one huge volcano, although Grimsvötn is much smaller than Yellowstone at 5 miles (8km) wide by 3.7 (6km) miles long.

Though Grimsvötn is buried under ice, the caldera crater is a lake, filled with water melted from the glacier by the heat of the magma beneath.

The dramatic blast at 9.50pm GMT on Monday was triggered by a build-up of magma that formed a cone in the caldera, which in turn raised the pressure pressure of the lake.

Ash and sulphur dioxide gas spewed out high into the atmosphere through a 3,300ft (1km) hole in melted in the ice.

As meltwater flows into the lake over the coming days, it is expected to overflow causing floods to the south of the volcano — a phenomenon known locally as "jökulhlaup". No towns lie in the area vulnerable to flooding, but a major trunk road is vulnerable.

Professor Bill McGuire, of the Benfield Hazard Research Centre at University College, London, said that this eruption was comparatively small. "It is not a particularly big one," he said. "You’d expect the main ash fall to go only 150km (93 miles) or so, so it isn’t going to have an effect on Britain even if the winds are right."

The same magma system, however, was responsible for the 1783 Laki eruption, which is among the most serious volcanic blasts ever to impact on this country. A 15-mile fissure pumped out a lake of lava covering 200 square miles over seven months — the largest lava flow in recorded history.

Scientists recently calculated that the eruption may have contributed to more than 10,000 deaths in Britain, as an estimated 143 megatonnes of toxic sulphur dioxide were discharged into the atmosphere.

It killed about 9,000 in Iceland — a quarter of the population— mainly as a result of famine as sheep died from eating contaminated grass.

Professor McGuire said: "The Laki fissue was connected to the Grimsvötn caldera, but nothing close to the same scale has happened since. It is still a relatively active caldera, but most of its eruptions are fairly small like this one, even if they do look spectacular."

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