Iceland Volcano Update: Eruption-Making Magma Shift May Be 'Days' Away

Another upward shift of magma through the Earth's crust under Iceland that has the potential to cause an eruption "could happen in the next few days or possibly after several months," as officials have expressed "considerable" uncertainty as to when the next volcanic episode might occur.

The Icelandic Meteorological Office said in an update on Wednesday that it was "not possible" to estimate when magma would next propagate upwards into a vertical dike beneath a peninsula to the southwest of the nation's main island—where an eruption was thought likely after a burst of seismic activity from November 10.

Last week, a decline in the number and severity of earthquakes around the magma intrusion led it to conclude that an eruption from the episode was less likely but still possible. However, experts have warned that volcanic activity in the region could pick up again.

Between 1,500 and 1,800 earthquakes a day were being recorded from November 10 for nearly two weeks, before dropping to the low hundreds.

The earthquakes have mostly occurred over and around the site of the magma dike—which is estimated to be around 9.3 miles long and runs alongside the coastal fishing town of Grindavik, on a southwesterly peninsula on Iceland's main island.

In recent weeks, authorities in Iceland have built earth walls, along with conduits and canals, around Grindavik and Svartsengi, a nearby geothermal power plant, in a bid to direct lava away from buildings in the event of an eruption. Grindavik's population of nearly 4,000 were also evacuated after cracks appeared in the ground.

When magma first propagated through the weak point in the Earth's crust near Grindavik, it was thought to have been within a half mile of the surface, and was being fed by a horizontal intrusion of magma under Svartsengi—around 6 miles in diameter and which has been pushing the ground up by around a centimeter (nearly half an inch) a day.

The Icelandic Met Office said on Wednesday that modeling suggested the flow of magma into the vertical dike had ceased, while it was still accumulating under Svartsengi, meaning "a new chapter may have begun with an increased chance of a new magma propagation and, subsequently, increased likelihood of an eruption."

It added that this sequence of events was likely to repeat itself, though the next propagation "might be on a smaller scale" and "could persist for several hours or days with an increased risk due to seismic activity and [ground] deformation."

The Icelandic Met Office said it was most likely that, if magma were to propagate from the horizontal intrusion again, it would move into the previously formed dike "making it the most likely area for an eruption."

A sudden shift in the North American tectonic plate away from the Eurasian plate is thought to have allowed magma to suddenly push upwards through a rift that runs between the two of them under Iceland.

One Icelandic volcanologist previously told Newsweek that while the volcanic episode may have ended, it may mark the start of an "intense" period of tectonic activity based on historic trends.

"We know that this is not the end of activity on the Reykjanes peninsula," Haraldur Sigurdsson, emeritus professor of geophysics at the University of Rhode Island, said, noting that much of Iceland's infrastructure—including the capital, Reykjavík—was located in the region.