Scientists have recorded "huge" carbon dioxide levels from Iceland's Katla volcano which has led to reports an eruption is imminent.
Katla, Icelandic for “kettle,” last erupted in 1918, and it is thought an eruption is overdue. This summer has seen an increase in seismic activity.
As one of Iceland’s largest and most active volcanoes, Katla is the volcano of greatest concern for Icelandic citizens.
Research has shown carbon dioxide levels emitted from the volcano have been “huge” in recent years and this was linked by some to a potential explosion in the near future.
However, the connection between this research and eruption claims is tenuous according to one of its authors, Evgenia Ilyinskaya, a research fellow at the University of Leeds, focused on volcanic gases and aerosol particles.
In a Twitter thread, Dr Ilyinskaya wrote: “We are in no position to predict whether Katla is 'about to erupt' or that ‘magma is building up’.”
Here is what you need to know about the Katla volcano:
Where is Katla?
Katla is situated in south Iceland, sitting in the Katla Geopark nature reserve.
The area is a hotspot for volcanic activity, with over 150 eruptions being recorded there since the 9th century.
Eyjafjallajökull is also situated there, a volcano renowned for causing widespread disruption to European travel in 2010.
How likely is it to erupt?
Over recent years, scientists have measured an increase in seismicity and an inflation of the volcano's caldera, which serves as a clear warning that an eruption is on its way, according to Icelandic tourist board Guide to Iceland.
Despite the warning signs, experts have said that because the volcano's cone is hidden beneath a glacier on a 5,000ft-high peak, assessing activity is difficult.
Sarah Barsotti, co-ordinator for volcanic hazards at the Icelandic Meteorological Office, said: "There is no way of telling when it will erupt, just that it will."
It's the CO2 levels being released by Katla that are causing the most concern, though - between 12 and 24 kilotons every day, according to the Geophysical Research Letters journal.
"It is well known from other volcanoes, for example in Hawaii and Alaska, that CO2 emissions increase weeks or years ahead of eruptions," said Evgenia Ilyinskaya, a research fellow in the Institute of Geophysics and Tectonics at Leeds University.
"This is a clear sign we need to keep a close eye on Katla. She isn't just doing nothing, and these findings confirm that there is something else going on."
Taking to Twitter, she wrote: "I said explicitly that we are in no position to say whether or not Katla volcano is ready to erupt; and that air traffic disruption in case of an eruption is unlikely to be as serious as in 2010."
There were previous worries that an eruption of Katla would "dwarf" that of Eyjafjallajokull in 2010.
Dr Ilyinskaya's comments formed part of a major backlash from the scientific community, who have said there is no reliable evidence to suggest that Katla will erupt at any time.
What will happen if Katla erupts?
Residents have been receiving routine evacuation training to prepare them for an eruption.
All mobile phones within the scope of a broadcast tower will get sent an alert warning them of present danger.
Farmers must also shut down their electric fences and allow their cattle to escape to higher ground.
If Katla erupts, the area could see days of ashfall, tephra clouds, lightning and glacial flash floods.
According to Guide to Iceland, there's also a possibility that Katla's ash cloud might affect European air travel.
How do volcanoes form?
A volcano is formed when magma rises through cracks in the Earth's crust, causing pressure to build up inside the Earth.
When this pressure is released, usually as a result of plate movement, magma explodes to the surface causing a volcanic eruption.
The lava from the eruption then cools to form a new crust. Over time, after several eruptions, the rock builds up and a volcano forms.