A decrease in seismic activity while magma continues to accumulate underground in Iceland has left scientists unsure of what may happen next, including whether an eruption would occur in the area they suspected it might.
In an update on Friday, the Icelandic Meteorological Office said that while the current volcanic process was “not over,” it was “difficult to say when and where” the next magma dike would intrude into the Earth’s crust below the island nation. Meanwhile, an intrusion of molten rock into the Earth’s crust that was deforming the surface continues to build “at a fairly stable rate.”
It said that in the prior few days, “relatively few” earthquakes had been detected, most of which had a magnitude of one or less. 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 a magma intrusion or dike—a rapidly forming, vertical sheet of molten rock that has pushed through a weak point in the Earth’s crust, and is estimated to be around 9.3 miles long. Its path runs alongside the coastal fishing town of Grindavik, on a southwesterly peninsula on Iceland’s main island.
The town of nearly 4,000 people was evacuated last month over the threat of an eruption.
Experts have so far believed that, if an eruption were to occur, it would most likely take place somewhere along the path of the dike. The Icelandic Met Office has previously said that the area had a high likelihood of eruption, before downgrading this to “possible” last week.
It said in its latest update that most of the seismic activity was occurring where the dike is thought to be fed by a horizontal magma intrusion a short distance away, which has been rising at a rate of around a centimeter a day, but that the ground around the dike was swelling much less than before.
The Icelandic Met Office said that the process that formed the dike would continue and “with certainty it can be stated that a phase has started where a similar sequence of events might repeat in time.” But it added: “At this stage, though, is difficult to say when the next energetic intrusion of magma at shallower depth might occur and if it will occur in a similar area or not.”
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.
In the horizontal intrusion under Svartsengi—around six miles in diameter and believed to be feeding the dike—magma continues to build at depth, which experts have previously said had been occurring cyclically for the past few years.
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 under Iceland.
When the seismic activity showed signs of decreasing, one Icelandic volcanologist expressed hope that the volcanic episode had come to an end, but told Newsweek that it may mark the start of an “intense” period of tectonic activity in the area based on historic trends.
Source : Newsweek