The “highly hazardous” and very active volcano is churning out carbon dioxide which suggests magma chambers below the surface are filling up, according to researchers.
Icelandic and British volcanologists believe the “huge” amount of gas being emitted by Katla could be a precursor to an eruption which would dwarf that of Eyjafjallajokull in 2010, the Sunday Times reports.
The eruption sent a massive cloud of volcanic ash into the sky which quickly spread across Europe forcing the cancellation of more than 100,000 flights.
A research report published in the Geophysical Research Letters journal found that Katla was releasing between 12 and 24 kilotons of carbon dioxide every day, making it “one of the largest volcanic sources of CO2 on the planet”.
The team behind the study said the volcano’s cone, hidden beneath a glacier on a 5,000ft-high peak, meant assessing its activity is difficult.
The report says Katla has been “undergoing significant unrest in recent decades”.
And by using high-precision measuring equipment, the researchers concluded the amount of gas being released now is much higher than previous estimates.
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.”
Evgenia Ilyinskaya, a research fellow in the Institute of Geophysics and Tectonics at Leeds University, told Icelandic national broadcasting service RUV, that the current CO2 levels suggested an eruption could be imminent.
She said: “There must also be a magma build-up to release this quantity of gas.
“It is well known from other volcanoes, for example in Hawaii and Alaska, that CO2 emissions increase weeks or years ahead of eruptions.
“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 going on.”
But others have played down the risk of an imminent eruption, saying the current CO2 levels are not necessarily higher than usual.
Magnus Tumi Guomundsson, a professor in geophysics at the University of Iceland, said more research is needed before any conclusions can be drawn.
In a Facebook post, he said a lack of historic data on gas emissions from Katla meant it is impossible to tell whether the massive amounts being produced now are normal.
He said: “Even more unclear is whether these massive emissions are directly connected to an underground magma chamber, or what [Katla’s] connection to the magma chamber in the volcano is.
“It’s possible that Katla works as a kind of vent or exhaust channel for gasses that are emitted from magma deep under the southern part of the volcano belt.”