Askja caldera, found in the remote highlands of Iceland, was responsible for a powerful eruption in 1875 which produced an ash cloud which reached Scandinavia. Since then, the volcano, which stands at 1,516 metres tall, has erupted on smaller scales – but experts believe it could be set to blow again for the first time since 1961. This is because there has been a major earthquake swarm in the past few days, with more than 500 tremors hitting.
Some believe this could be sign of an impending eruption.
Volcano monitoring site Volcano Discovery said: “An swarm of earthquakes is occurring near the Askja caldera, in an area approx. 10 km ENE from the rim and at depths around 5km.
“More than 550 small quakes have been recorded during the past 5 days, but so far, most quakes have been tiny. The largest events were two shocks with magnitudes 3.2 and 3.4, felt by local residents.
“The swarm is likely caused by an intrusion of magma into an underground fissure (dike), which could but not necessarily must (and most often does not) lead to an eruption.”
Indeed some geologists do believe a series of tremors can be a precursor for a volcanic eruption.
Portland State University Geology Professor Emeritus Scott Burns has said: “If you get swarms under a working volcano, the working hypothesis is that magma is moving up underneath there.”
Many global travellers will still have memories of the last time an Icelandic volcano massively erupted.
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However, Oraefajokull poses even more of a threat than any other Icelandic volcano.
The volcano in south east Iceland stands at a height of 2,110 feet, making it the highest peak in the Nordic nation.
If Oraefajokull were to erupt for the first time since 1727, it could cause as much damage as the Eyjafjallajokull volcano in 2010.