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There could be very little warning of eruption starting

10.03.2021 - 12:40
©Kristinn Ingvarsson
 Mynd: Háskóli Íslands - Kristinn In
The flow of magma that is rising into the crust between Keilir and Fagradalsfjall on the Reykjanes peninsula is believed to be up to four-times greater than the flow of Elliðaá river on the outskirts of Reykjavík. The start of an eruption may come with very little warning, one geophysicist tells RÚV.

Scientists are following the magma movements under the Reykjanes peninsula as closely as they can and they know that the intrusion has grown and the flow increased in recent weeks.

The magma dyke is only about one metre wide, but seven kilometres long and has moved some two to three kilometres further south over the past two weeks. At the bottom of the dyke, some five kilometres below the ground, is a channel that is allowing 15-20 cubic metres of magma per second through—which is three or four times more flow than Elliðaá river. It is believed the top of the dyke is now around one kilometre below the ground at the south and closer to two kilometres near to Keilir. The lava field closer to the south of the dyke is also warmer, so it is considered a more likely location for molten lava to break the surface. 

Most activity at the southern end 

If magma continues to flow into the dyke, it is clear it will continue to expand, and it does so by following the path of least resistance. This makes it more likely either that the southward expansion will continue, or that the magma will break through the surface in the form of an eruption. 

“The most activity has been at the southern end of it. Maybe the magma has begun to solidify at the northern end of the dyke, making it less likely it will break the surface there. So it is the southern end we are looking at, because of the earthquakes and also crust movements show that there have been changes there in the past days,” says Freysteinn Sigmundsson, geophysicist at the University of Icealand. 

Could be similar to Fimmvörðuháls 

If an eruption takes place, Freysteinn believes it could be of a similar size to the Fimmvörðuháls eruption in 2010, judging by the amount of magma believed to be entering the dyke. The 2010 Fimmvörðuháls eruption lasted from 20th March to 13th April and proved a popular tourist attraction. It was all but forgotten when the much larger Eyjafjallajökull eruption started nearby on 14th April. Unlike South Iceland, the Reykjanes peninsula does not have any central volcanoes capable of producing large, explosive eruptions like Eyjafjallajökull, geologist Helga Kristín Torfadóttir explained to RÚV English last week. 

The likely eruption on the Reykjanes peninsula could start at any time and with very little warning. “Where it has come down to, at maybe a kilometre to the surface, it can be expected that there might not be very clear signs, no clear warning of the change that brings it up to the surface. Small earthquakes, a small volcanic tremor, and there could be an eruption with very little warning, I think,” Freysteinn says. 

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