Volcano erupts in Iceland after thousands evacuated from town

Molten rock has been spewing spectacularly from fissures in the ground after a volcano erupted in Iceland following weeks of intense earthquake activity.

The Icelandic Meteorological Office said the lava is emerging from a crack in the Reykjanes peninsula, which was around 3.5km (two miles) long and had grown rapidly.

Lava 'may head towards nearby town' - live updates

An evacuation had taken place in recent days, moving nearly 4,000 people out of the fishing town of Grindavik in the country's southwest, as fears grew of an eruption.

The moment the eruption began was caught on grainy video as a flash of light illuminated the sky at 10.17pm local time on Monday.

There have been several eruptions in unpopulated areas in the peninsula in recent years, but authorities said the new one was believed to pose an immediate risk to the town.

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What is happening under the surface?

'This is a big eruption'

The Icelandic Met Office issued its first alert after the eruption on Monday.

It said seismic activity and GPS data suggested the magma was moving southwest, and the eruption "may continue in the direction of Grindavik".

Vidir Reynisson, head of Iceland's civil protection and emergency management, told the country's public broadcaster RUV: "The magma flow seems to be at least a hundred cubic meters per second, maybe more.

"So this would be considered a big eruption in this area at least."

Local police said they had raised their alert level as a result of the eruption.

The country's civil defence has also warned the public not to approach the area.

The nearby Blue Lagoon geothermal spa has also been closed as a precaution.

Eruption produced 'a lot of lava'

But Volcanologist Haraldur Sigurdsson told Sky News the lava is unlikely to reach populated areas.

"It certainly is a problem, but fortunately this is in a remote area," he said.

"This is a type of eruption where you don't get explosions, these are fountains of magma.

"They are caused by the pressure of the magma moving up and the gasses that are contained.

"It produces a lot of lava, which turns then turns to rock and adds to Iceland."

'These eruptions can last for months'

All scientists can do now is continue monitoring the situation, volcanologist Dougal Jerram told Sky News - as he warned there's no way of predicting how long the eruption will last.

"These eruptions can often last for several days, sometimes months, and in the most extreme examples, several months," he said. "One of the good things is [that] the actual place the magma has come out to the surface is actually about 3km north of Grindavik.

This means that "at the moment, there's no imminent danger to the infrastructure locally," he continued.

"The key thing now is monitoring it [and] making sure it's contained in a certain topographical area."

Monitoring the flow of magma and lava isn't easy. Dr Sam Mitchell, an associate in volcanology at the University of Bristol, said: "One of the challenges facing the monitoring is that south west Iceland is at a time of near constant darkness this close to the winter solstice.

"Even though the glow of lava is more observable during darker hours, it makes assessing larger areas of land and impact a little more challenging."

British holidaymaker awaits flight news

The nearby international airport in Reykjavik, Iceland's capital, has remained open.

British holidaymaker Helen Hope was on a plane waiting for her flight back to Manchester to take off.

She told Sky News: "Most people were intrigued by it.

"People possibly started worrying more as we were delayed longer.

"Some passengers noticed it and then people were scrambling to have a look.

"The pilot has been waiting for the OK from various people in charge of safety to check which way the wind and any ash is blowing."

Professor Matthew Watson, professor of volcanoes and climate at the University of Bristol, said: "It is unlikely, but not impossible that there may be some impact on air travel, although this type of eruption doesn't generally produce much ash which is what tends to ground planes.

"This style of eruption is amongst the most spectacular ever seen and there will be a strong pull for tourists, even though the Blue Lagoon complex has again shut.

"Tourists should strictly follow official advice as there are significant hazards, such as new breakouts, which can quickly put people in harms way."

Area was on alert for weeks

Iceland was put on high alert for a volcano eruption in November when a state of emergency was declared.

The Reykjanes peninsula, a volcanic and seismic hot-spot around 30 miles southwest of Reykjavik, had been shaken by hundreds of small earthquakes every day for more than two weeks.

Authorities were working on a plan to protect the evacuated town of Grindavik from a volcanic eruption.

Scientists believed the most likely site for magma to break through the surface was a short distance from the town, and it could flow towards houses.

But Almannavarnir, the Icelandic civil defence, said earth walls would be built to divert a river of molten lava away from the town.

Located between the Eurasian and the North American tectonic plates, among the largest on the planet, Iceland is a seismic and volcanic hotspot as the two plates move in opposite directions.