Scientists disagree over whether Reykjanes eruption sequence is ending

Scientists disagree over whether volcanic activity at Sundhnukar is nearing its end, with some also differing over the danger to Grindavik, mbl.is reports. The land around Svartsengi continues to rise, but researchers interpret what that signals differently.

Volcanologist Thorvaldur Thordarson says activity at Sundhnukar may be ending, if it has not already. He notes that land uplift is much slower than at its peak and has remained fairly steady in recent months. He has not analysed the measurements in detail, but says the chance of another eruption decreases as the pause grows longer. He does not rule one out.

If an eruption occurs, Thordarson considers the area between Sýlingarfell and Stora-Skogfell the likeliest starting point, as with most earlier eruptions. He expects lava would probably follow routes similar to those taken before, with the protective barriers continuing to serve their purpose. In his view, the chance of an eruption within Grindavik’s town limits is negligible at this point.

Thordarson considers Grindavik and the Blue Lagoon relatively safe, but says open fissures in Grindavik still require the utmost caution.

Geophysicist Pall Einarsson says the unrest is still ongoing. He stresses that his speciality is earthquakes, crustal deformation and the lead-up to eruptions, while Thordarson specialises in rock and the material released during eruptions. Einarsson says he has based his assessment on the Icelandic Meteorological Office’s expert group and colleagues at the University of Iceland.

Einarsson views developments since the ground began rising at Svartsengi in January 2020 as one continuing sequence of events, and says the uplift is central to assessing what may happen next. He says the measurements do not support concluding that the unrest is ending, and cautions against downplaying the danger to Grindavik residents.

He does not rule out activity fading, but describes that as one of several possible scenarios. He leans towards the Icelandic Meteorological Office’s assessment that another magma intrusion from Svartsengi towards the Sundhnukar crater row, possibly followed by an eruption, remains likely. He cannot say when that might happen.

In an assessment dated September 30, the Meteorological Office said slow ground uplift was continuing at Svartsengi and seismic activity remained low. It said there was no evidence that the eruption sequence was ending and that little warning time should still be expected. Measurements would need to show clear signs of the sequence ending over an extended period before it could be declared over, the office said. Even if magma accumulation stops for several months, it could resume.

Einarsson said there might not even be a measurable precursor before the next eruption. He pointed to experience at Krafla, where warning signs became less distinct as the number of eruptions increased.