Some 8,000 tremors have been measured on the Reykjanes peninsula since January, the Icelandic Met Office reports. While the vast majority of these have been relatively small, it is very likely that there is now a new magma intrusion in the area.
Last January, seismic activity in southwest Iceland grew to such a degree that the Department of Civil Protection and Emergency Management declared a “state of uncertainty”. This activity was marked not just by earthquake swarms but also a measurable swelling of the ground near the volcano of Mt. Þorbjörn.
The area has been closely monitored since, and on March 26th the Scientific Advisory Board met to go over their findings. Not only were thousands of tremors recorded in and around the area, but the total elevation of the ground-swelling uplift was measured at 7-8cm over this entire period.
“The Scientific Advisory Board still believes that the most likely explanation of the uplift is a magma intrusion where the magma is ‘forcing’ its way horizontally between the stratum in the crust and forming a thin sill at about 3 to 4 km depth,” the summary of an earlier meeting reads in part. “The magma intrusion causes considerable amount of earthquakes in the area north of Grindavík.”
It bears mentioning that magma accumulation does not necessarily mean that an eruption is imminent. Volcanic activity is notoriously unpredictable, and it is entirely possible that nothing comes of this. The earthquake swarm has also decreased in activity recently, and in fact earthquakes in this area are not unusual.
Further, it must be emphasised that there is no such thing as a volcano being “overdue” for an eruption. That is not how volcanoes work. Mt. Þorbjörn last erupted in 1211 and lasted roughly until 1240, but that is by no means an indication that the volcano is on some kind of regular schedule to erupt.
All this being the case, scientists are still monitoring the situation closely. The earthquakes have been felt repeatedly by residents of nearby Grindavík, and in some cases have been felt as far away as Reykjavík.
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