Faster volcanic pulse more like activity this spring

14.09.2021 - 13:23
Mynd með færslu
 Mynd: Sigurður Helgason - RÚV
The 'pulse’ of the Fagradalsfjall volcano strengthened overnight and molten lava is now erupting from the crater around eight times per hour.

The volcano seems to have shifted into yet another new phase, after nine days of calm, it has returned to a pattern of activity last seen in the spring. “The pulses started yesterday afternoon, around four, and then last night they became more regular and now this morning we are seeing pulse activity that is very similar to what we saw in April and May. We have around eight pulses per hour,” says Kristín Jónsdóttir, Met Office natural hazards specialist. “There has been a great deal of activity in this most recent wave.”

What explains this pulse activity? Kristín says it is reminiscent of a geyser. “This pulse activity, it seems to be like what happens in geysers, and what controls this pulsing activity is actually the size of this reservoir which is underneath and how long it takes to fill it, et cetera,” Kristín says. 

Lava piling up rather than spreading out 

The crater rim now reaches 334 metres above sea level and the latest measurements from the University of Iceland estimate that there is 143 million cubic metres of lava spread over the lava field which covers 4.6 square kilometres of land. 

The area of the lava field has increased very little in the past month, as molten lava is not reaching the edge. Instead of getting wider, the lava field is getting thicker and the crater has become a small, but very steep shield volcano. 

Between 8th August and 2nd September, there were 16 pulses of volcanic activity during which lava flow was powerful, but there was little visible activity in between. During quiet periods, the crater was completely empty to a depth of at least 70 metres. Then, from 2nd to 11th September, the volcano went completely quiet during its longest pause by far to date. 

Scientists say there is no way to predict when the eruption will finish based on its patterns of behaviour to date. 

Continued Askja uplift 

The civil protection agency issued an uncertainty alert for Askja volcano in the central highlands last week, but there has been no news of volcanic activity since. “This uplift is continuing and we have seen a little bit of seismic activity as well,” Kristín says. 

“This is, of course, very significant, because what we have been seeing since records began in 1970, from that time until now it has been subsidence of an average of five centimetres a year, and then now, just since the start of August, there are six centimetres that the land there has risen.” 

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