An unusually large and powerful eruption of an ice-covered gravitational volcano on Iceland in 2011 sent 20 kilometers of ash into the atmosphere, canceling about 900 passenger flights. In comparison, about 100,000 flights were canceled in 2010 due to very small explosions in Izzafallajukul.
Understandably, any mention of another volcanic eruption from an Icelandic volcano would also raise concerns in the air travel industry, which is currently associated with the Kovid-19 epidemic.
But there are clear indications that the Gramsvaton volcano is about to erupt again. As a result, authorities have recently raised the level of risk for the volcano.
Gríswötön is a strange volcano, as it lies almost entirely beneath the ice, and the only permanently visible part is an old belt on its south side that forms the edge of a huge crater (a calcare). And it’s under the ice, along the base of this belt, that most recent eruptions have occurred.
Another peculiarity is that the heat output from the volcano is extraordinarily high (2000-4000 MW), and this overlay melts the ice and forms a hidden subglacial lake of molten water. It is deep up to 100 meters (328 feet) deep and has about 260 meters (850 feet) thick floating ice on it. Fresh ice is constantly flowing into the caldera, where it melts, and so the water level just keeps rising and rising.
This molten water can suddenly escape, and after traveling south under about 45 kilometers of ice it emerges like a flood on the margins of ice, which has washed away roads and bridges in the past. Luckily, melting water under the ice can find its way to its outlet, and so roads are closed in good time to prevent passengers from getting stuck and dying in the flood.
Yet another important peculiarity of the Gramsvaton is that it can have a hair-trigger response to pressure. This happens when the gutters of the molten lake – removing water from the top of the volcano – quickly reduce the pressure.
This can cause an outbreak – it’s like squeezing off the pressure cooker. This has happened many times on Gramsvaton.
Iceland’s most frequently erupting volcano is Gramsvatan, and some 65 eruptions in the last 800 years have been known with some certainty. The time interval between explosions varies – and, for example, before most 2011 outbreaks, there were small outbreaks in 2004, 1998 and 1983 with gaps of four and 15 years.
Crucially, and with the forthcoming eruption in mind, the pattern of most large eruptions in Gramsvatan appears every 150-200 years (e.g., 2011, 1873, 1619), between smaller and more frequent eruptions, about one in almost a decade Occurs once a decade. .
A hole about 1.5 km wide melted into ice since the 2011 eruption. (Dave McGarvey)
Signs of activity
The frequency of volcanic eruptions allows scientists to find patterns that erupt (predecessors). And if this is repeated every time a volcano erupts, it is possible for scientists to have more confidence that an eruption is likely in the near future.
Being specific about a particular day is hardly possible though.
Since the 2011 eruption, Icelandic scientists have been carefully monitoring the gravitational field, and have seen various signs indicating that the volcano is ready to erupt.
Old Ridge of Gramsvaton. (Dave McGarvey)
For example, a volcano is spreading new magma into the plumbing system beneath it (consider burying a balloon in the sand and then inflating it). More ice is melting due to an increase in thermal activity and there has also been a recent increase in seismic activity.
So what happens Again, depending on the manner in which past eruptions have been observed, a few hours (one to ten hours) of intense earthquakes will indicate that the magma is moving toward the surface and that the eruption is imminent. In cases where a hidden subglacial lake fills up and erupts, an earthquake occurs just after the lake sinks and before it erupts.
Small Gramsvaton eruptions consume a lot of energy when they interact with water and ice on the surface. This means that the resulting ash becomes wet and sticky and therefore falls relatively quickly from the sky.
Ash clouds therefore travel only some ten kilometers from the place of explosion. This is a great view for the people of Iceland and also for air travel, as it prevents the formation of significant ash clouds that can flow around and close the airspace.
But will it be a small explosion? If the past pattern of the occasional large eruptions of Gramsvatan continues in the future, the next eruption should be a smaller one (given that it was larger in 2011). And here the word “word” is important – Iceland’s volcanoes are complex natural systems and patterns are not always followed confidently.
Dave McGarvey, Volcanologist, Lancaster University.
This article is republished from the talk under the Creative Commons license. Read the original article.
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