Just for another perspective, here's another article from mbl.is with a different UI volcanologist, Ármann Höskuldsson, earlier this evening: https://www.mbl.is/frettir/innlent/2023/11/12/telur_gos_liklegra_i_eldvorpum/ I don't know if Ármann knew about the trough at the time of the interview - he and Þorvaldur are colleagues but it could be a very recent discovery or it could be that they simply disagree. We often see different perspectives from the different volcanology media stars!
Article:
"We have greater expectations of something happening in the Eldvarp fissure," says Ármann Höskuldsson, volcanologist at the UI Institute of Earth Science.
In recent days, an eruption in the Sundhnúkar crater line has been thought the most likely scenario, based on scientific measurements. Ármann, however, believes that the Eldvarp fissure is a more likely eruption site. It is not possible to rule out other possibilities, however.
Following significant seismic activity on Friday, it came to light that a 15 km long magma tunnel had formed under Grindavík, south west of the Sundhnúkar crater line. Scientists have been concerned that magma could reach the surface in that area.
Speaking to mbl.is that evening, Ármann said he expected an eruption to occur in the Eldvarp fissure or north west of Þorbjörn, rather than east of Grindavíkurvegur road by Sundhnúkar.
Ármann says he still thinks this scenario more likely and his opinion has not changed.
"But something happened on Friday, in the Sundhnúkar elevation, which was unexpected, because everyone was focusing on the Eldvarp fissure and the Illahraun craters," he says. The magma intrusion that formed on Friday opened up the possibility of an eruption above Grindavík.
Ármann says that an eruption could still occur in the Sundhnúkar craters. If something happens it could happen by Sýlingafell. In that case, people would have time to try to divert the lava before it flowed past Grindavík.
"If it's there in Sýlingafell, as it appears to be at the moment, that's maybe better news than we had on Friday, when the intrustion extended right under the town."
He says it came as a great surprise to him to see the magma intrustion reach so far south. Because there were very clear signs of uplift in the Eldvarp fissure and Illahraun craters, which were not seen to any great extent in the Sundhnúkar fissure.
"On the other hand, we have to consider that this is a plate boundary. The plates are moving apart because the tension has become too high. So in this sense, this is perhaps not a surprise.
In the Sundhnúkar fissure the magma accumulation has not been as significant as in other places.
"It's possible that this was the release of tectonic stress. Then naturally the magma has risen. But for some reason it can't make it to the surface."
Ármann says this would be good news. Divergence of the tectonic plates has, though, caused significant damage in Grindvík.
The cracks that have formed in Grindavík don't necessarily mean that magma is making its way to the surface.
"We saw this clearly at Krafla. There was a lot of activity but an eruption never occurred."
Ármann hopes that this movement is over. "Then the likelihood of an eruption would dwindle gradually," he says. It would then be more likely that activity would continue in the Eldvarp fissure, where there is more room for an eruption.
As to when an eruption might happen, Ármann says that it will probably occur within a few days. "It's a question of whether there's an eruption in the Sundhnúkar fissure, or whether the major movements there are over and things will continue in Eldvörp or Illahraun."
The situation will become clearer with more data collected over the next few days.