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Iceland Has Major Quake Swarm At Reykjanes Peninsula

 Reykjanes, Iceland is experiencing another major quake swarm, with the largest quake so far at magnitude 5.7. The swarm is in the same general area as previous seismicity within recent years, and is very probably related to more magma intrusion. Magma intrusion and system inflation has been going on for about two years in this area, which is frequented by tourist visiting the famous Blue Lagoon resort spa. 

Screen snip from Iceland Met Office website showing the large quake swarm. Green stars denote temblors larger than magnitude 3.
 The quake swarm is assumed to be related to the inflation of the Reykjanes volcanic system, however the area is host to numerous volcanic centers, and it is unclear whether they are also being activated by the recent magma intrusions. In the same area as the quake swarm is the Krisuvik volcanic system, and the Pleistocene Fagradalsfjall system. To the slight East of the swarm, there is the Brennisteinsfjöll system as well.
Icelandic news has reported that after an overflight of the Reykjanes area, new steaming vents have opened up under cooled lava flows, and could be seen from the air. A hazard level has been declared, to give the local authorities the tools they need to coordinate disaster management activities should more tremors cause damage to nearby towns, or, if an eruption should occur.
Eruptions in the area have occurred in historical times, with the most recent confirmed eruption occurring in 1830. The last quake of similar magnitude was a 5.6 quake that was followed by some 1,700 aftershocks in late October of 2020. This did not result in an eruption, however deformation was recorded, including uplift of several cm. Gas odors have also been reported after the large quakes, which suggests that either rock fracture is releasing stored gases, or new magma is increasing gas venting. 
In either case, magma is certainly involved, and if the area continues to experience large dike intrusions, the likelihood of an eruption in the area increases with each swarm.
It is unclear whether this sequence will lead to an eruption. Reports from Jon Frimann's blog suggest that Iceland has raised the aviation color code over Reykjanes to Yellow (caution), so it does seem that at least some people think the situation warrants watching.
An eruption would probably threaten the Blue Lagoon, the town of Grindavik, and possibly the towns north of the eruption with pahoehoe lava flows, and gases. While submarine eruptions have had episodes of VEI 3-4, the land eruptions have been largely effusive, so it is probably not going to be the same as when Eyjaflallajökull or Grimsvötn erupted with large ash clouds. | Impressum