Reykjanes Earthquake Swarm: Magma Accumulation Suspected, Eruption a Possibility Skip to content

Reykjanes Earthquake Swarm: Magma Accumulation Suspected, Eruption a Possibility

By Gréta Sigríður Einarsdóttir

Melissa Anne Pfeffer conduction gas tests at the Reykjanes Peninsula
Photo: Sara Barsotti via the Iceland Meteorological Office. Melissa Anne Pfeffer conduction gas tests at the Reykjanes Peninsula.

New data from the ongoing earthquake swarm on the Reykjanes peninsula suggests magma is accumulating underneath Fagradalsfjall mountain, according to scientists at the Icelandic Met Office. Experts say there is a chance the earthquake swarm could lead to a volcanic eruption, but it is not likely to be very dangerous or threaten inhabited areas.

The earthquake swarm that began on Reykjanes six days ago continues, now mostly in the vicinity of Mt. Keilir and Trölladyngja. The frequency of quakes dropped slightly last night but after 10.00pm it increased again. Four earthquakes over M4 occurred last night, the largest at M4.6. In the past two days, around 2,100 earthquakes have occurred on the Reykjanes peninsula, about 100 of which were larger than M3. The quakes have been felt in the Reykjavík capital area as well as across South and West Iceland.

Experts Meet to Discuss Possible Scenarios

The Department of Civil Protection and Emergency Management’s Scientific Advisory Board met yesterday to discuss the earthquake swarm on the peninsula. Present at the meeting were representatives from the Met Office, the University of Iceland, The Environment Agency of Iceland, Isavia, HS Orka, and ÍSOR. The Board went over InSAR (Interferometric Synthetic Aperture Radar) images they received yesterday, which show more land movement in the area in the last few days than had been detected earlier. Earthquake Hazards Co-ordinator at the Icelandic Met Office Kristín Jónsdóttir told RÚV that while earthquakes could cause movement of a few centimetres, the new data shows land has shifted by up to 30 centimetres in some areas. The most likely explanation is that a magma passage is forming underneath the area where the earthquakes originate. Scientists will be working with the new data to create models that might cast a clearer light on the development.

In light of the new data, scientists have projected five possible scenarios:

  • The seismic unrest will die down in the next few days or weeks.
  • The seismic unrest will pick up, culminating in an earthquake up to M6 originating close to Fagradalsfjall.
  • The seismic unrest will pick up, culminating in an earthquake up to M6.5 originating close to Brennisteinsfjöll.
  • The magma intrusion continues close to Fagradalsfjall but the activity dies down and the magma solidifies.
  • The magma intrusion continues, culminating in a fissure eruption and lava flow that will likely not threaten inhabited areas.
Iceland Met Office. The latest data of InSaR images gotten from Sentinel-1 yesterday. The image shows more movement than registered before in the area where the earthquakes are most active

Eruption Would Not Threaten Inhabited Areas

As activity in the Reykjanes peninsula is fluctuating, it is difficult to predict which scenario is most likely. Scientists are expecting to acquire new data later this week that may cast a clearer light on the reasons for the earthquakes. The Scientific Advisory Board will meet again today to further assess the data at hand. Kristín stresses that the location of the earthquake activity is far enough from inhabited areas that even a medium-sized lava flow would not affect people.

Geophysicist Magnús Tumi Guðmundsson and volcanologist Þorvaldur Þórðarson went over the possible eruption in last night’s television program Kastljós, stating that a possible eruption close to Keilir would not be a large one and the lava would not flow quickly. It would mostly consist of lava production and wouldn’t be very explosive. For those worried that an eruption could cause an ash cloud (like the one that stopped air traffic in Europe in 2010) the scientists stated that data suggests the possible eruption would not produce much ash. While no inhabited areas would be threatened, it’s possible that the road across the peninsula, which links Reykjavík and the international airport in Keflavík, would be damaged. Both scientists interviewed on Kastljós stressed that even if magma accumulation was in fact occurring under the earthquake zone, that didn’t mean the earthquake swarm would end with an eruption. An eruption on the Reykjanes peninsula is as likely to happen in the coming weeks as in a century or two.

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