It’s already been a pretty explosive year, but things could still escalate as Iceland’s most active volcano looks like it’s getting ready to erupt.
The ice-covered Grímsvötn active volcano looks set to end 2020 with a bang, as warning signs of an eruption have prompted the Icelandic Met Office to raise the threat level for the giant mass from green to yellow.
Explaining the decision to change the threat level, the Met Office wrote:
Multiple datasets now indicate that Grímsvötn volcano has reached a level of unrest, comparable to that observed prior to historic eruptions.
For these reasons, the aviation color code has changed from green to yellow. This does not mean that an eruption is imminent.
However, an eruption could be triggered by depressurization if the subglacial lake inside the caldera will drain and cause a flood or occur regardless, possibly with very weak precursory activity and short warning time, as seen in the eruption of 2011.
The conditions at the volcano may change at any given time and the volcano may return to normal background conditions without further escalation.
Grímsvötn is an unusual volcano as it lies almost entirely beneath ice, with the only permanently visible part being an old ridge on its south side.
The volcano hasn’t been lying dormant for long, as in 2011 it produced a large and powerful eruption from the base of the exposed ridge. The explosion sent ash 20km into the atmosphere and caused the cancellation of about 900 passenger flights.
Following the eruption in 2011, Icelandic scientists have been monitoring Grímsvötn for signs it may erupt. Detailing the clues in The Conversation, McGarvie said the volcano has been inflating as new magma moves into the plumbing system beneath it – a process likened to ‘burying a balloon in the sand and then inflating it’.
An increase in thermal activity has been melting more ice around the volcano, and there has also been a recent increase in earthquake activity.
Using knowledge from past eruptions, experts have determined that an intense swarm of earthquakes lasting between one and 10 hours will signal that magma is moving towards the surface and that an eruption is imminent.
Gaps between eruptions can vary between four and 15 years, with previous, smaller eruptions taking place in 1983, 1998 and 2004. The volcano appears to have a pattern of infrequent larger eruptions that occur every 150-200 years, for example in 1619, 1873 and 2011.
The fact that Grímsvötn produced a large eruption in 2011 suggests the next eruption should be a small one, though the volcano may not necessarily stick to the pattern it has established in the past.
Originally published at Unilad