The ice-covered Grímsvötn volcano on Iceland produced an unusually giant and highly effective eruption in 2011, sending ash 20km into the ambiance, inflicting the cancellation of about 900 passenger flights. Compared, the a lot smaller 2010 eruption of Eyjafjallajökull led to the cancellation of about 100,000 flights.
Understandably, any point out of one other explosive eruption from an Icelandic volcano will elevate considerations within the air journey business, which is presently reeling from the COVID-19 pandemic. However there are clear indicators that the Grímsvötn volcano is on the brink of erupt once more. Consequently, the authorities have lately raised the menace degree for this volcano.
Grímsvötn is a peculiar volcano, because it lies nearly wholly beneath ice, and the one completely seen half is an outdated ridge on its south facet which varieties the sting of a giant crater (a caldera). And it’s alongside the bottom of this ridge, below the ice, that almost all current eruptions have occurred.
One other peculiarity is that the warmth output from the volcano is awfully excessive (2000-4000MW), and this melts the overlying ice and produces a hidden subglacial lake of meltwater. That is as much as 100 metres deep and has ice as much as about 260 metres thick floating on it. Recent ice is regularly flowing into the caldera, the place it melts, and so the water degree simply retains rising and rising.
Dave McGarvie, Writer offered
This meltwater can escape instantly, and after travelling southwards beneath the ice for about 45km it emerges on the ice margin as a flood, which previously has washed away roads and bridges. Luckily, the passage of meltwater beneath the ice to its outlet will be tracked, and so roads are closed in good time to keep away from travellers getting caught within the flood and killed.
One more necessary peculiarity of Grímsvötn is that it could have a hair-trigger response to stress. This occurs when the meltwater lake drains – elimination of the water from throughout the highest of the volcano quickly reduces the stress. This could set off an eruption – it’s like lifting the lid off a stress cooker. This has occurred many occasions at Grímsvötn.
Grímsvötn is Iceland’s most often erupting volcano, and over the previous 800 years some 65 eruptions are identified with some certainty. The time gaps between eruptions are variable – and, for instance, previous to the bigger 2011 eruption there have been smaller eruptions in 2004, 1998 and 1983 with gaps of between 4 and 15 years. Crucially, and with the following eruption in thoughts, Grímsvötn seems to have a sample of rare bigger eruptions that happen each 150-200 years (for instance 2011, 1873, 1619), with smaller and extra frequent eruptions occurring roughly as soon as a decade in between.
Indicators of exercise
A excessive frequency of eruptions at a volcano permits scientists to detect patterns that result in eruptions (precursors). And if these are repeated every time a volcano erupts then it turns into doable for scientists to be extra assured that an eruption is prone to occur within the close to future. It’s, nonetheless, seldom doable to be exact in regards to the actual day.
Dave McGarvie, Writer offered
Icelandic scientists have been rigorously monitoring Grímsvötn since its 2011 eruption, and have seen varied alerts that recommend the volcano is on the brink of erupt. For instance, the volcano has been inflating as new magma strikes into the plumbing system beneath it (consider burying a balloon within the sand after which inflating it). Rising thermal exercise has been melting extra ice and there has additionally been a current improve in earthquake exercise.
So what occurs subsequent? Once more, primarily based on the sample noticed at previous eruptions, an intense swarm of earthquakes lasting a couple of hours (one to 10 hours) will sign that magma is transferring in the direction of the floor and that an eruption is imminent. In circumstances the place the hidden subglacial lake drains and triggers the eruption, the earthquakes happen after the lake has drained and simply earlier than the eruption.
The smaller Grímsvötn eruptions expend a whole lot of power after they work together with water and ice on the floor. Meaning the ensuing ash will get moist and sticky and so falls from the sky comparatively rapidly. Ash clouds subsequently solely journey a couple of tens of kilometres from the eruption web site. This can be a good state of affairs for Icelanders and likewise for air journey, because it prevents the formation of considerable ash clouds that would drift round and shut off airspace.
However will or not it’s a small eruption? If Grímsvötn’s previous sample of occasional giant eruptions with extra quite a few smaller eruptions occurring in between continues into the long run, then the following eruption needs to be a small one (given there was a big one in 2011). And the phrase “ought to” is necessary right here – Iceland’s volcanoes are advanced pure programs and patterns will not be all the time adopted faithfully.
Dave McGarvie doesn’t work for, seek the advice of, personal shares in or obtain funding from any firm or organisation that may profit from this text, and has disclosed no related affiliations past their tutorial appointment.