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Iceland’s Most Active Volcano is Ready to Erupt Again

The Grímsvötn​ volcano located in Iceland, a structure mostly covered in ice, caused an unprecedentedly massive and powerful eruption back in 2011, discharging ash 20 kilometers (12.42 miles) into the atmosphere and causing more than 900 passenger flights to cancel.

By comparison, the smaller eruption of Eyjafjallajökull, recorded in 2010, led to the cancellation of about 100,000 flights. These events make any mention of another explosive eruption from an Icelandic volcano raise concerns in the air travel segment.

However, there are signs that the Grímsvötn​ volcano is on the edge of erupting again, and as a result, the authorities have recently raised the threat level for the volcano.

Grímsvötn​’s Peculiar Features

Grímsvötn​ is a rather bizarre volcano, as it is almost all covered in ice, with the only permanently visible part beings an old ridge on its south side, which forms the margins of a massive caldera. It is along the base of this ridge, beneath the ice, that most recent eruptions have taken place.

Another oddity is that the heat discharge from the volcano is incredibly high – around 2000 to 4000 MW – melting the sheets of ice covering it and producing a hidden subglacial lake of meltwater. This meltwater can get out suddenly, and after traveling southwards underneath the ice for around 45 kilometers ( 27.96 miles), it appears at the ice edge as a flood.

The hole melted in the ice by the 2011 eruption. [Image Credit: Dave McGarvie, Lancaster University]
Yet another peculiarity of Grímsvötn​ is that it can have an instantaneous response to pressure. This occurs when the meltwater lake drains, and removal of the water from across the top of the structure rapidly decreases the pressure. These events can cause an eruption, and it has happened many times in the past.

Signs of Activity

A high occurrence of eruptions at a volcano enables researchers to identify patterns – also known as precursors – that lead to eruptions. If these are repeated every time a volcano explodes, it becomes possible for experts to predict that an eruption is likely to take place in the near future.

It is, however, rarely possible to be accurate about the exact day. Icelandic researchers have been monitoring Grímsvötn​ since its 2011 explosion and have recorded various signals that imply the volcano is preparing to erupt.

The old ridge of Grímsvötn. [Image Credit: Dave McGarvie, Lancaster University]
For instance, the volcano has been swelling as new magma travels into the plumbing system underneath it. Enhancing thermal activity has been melting more ice, and there has also been recorded a recent rise in earthquake activity. Based on the pattern seen at previous eruptions, a massive swarm of earthquakes lasting a few hours will indicate that magma is traveling to the surface, and an eruption is on the way. 

The smaller Grímsvötn​ explosions consume a lot of energy when they engage with water and ice at the surface. This means the ensuing ash gets wet and viscid, which makes it fall from the sky rather quickly; moreover, ash clouds only move a few tens of kilometers from the eruption site.

This is a good scenario for Icelanders and also for air travel, as it doesn’t allow the formation of thick ash clouds that could travel around and close off airspace. However, will it be a small eruption? If Grímsvötn’s observed pattern of seldom large eruptions with multiple smaller explosions taking place in between continues into the future, then the next eruption should be a small one.

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