The earthquake swarm that began just SSW of Keilir in the Reykjanes Peninsula, Iceland on September 27, 2021, has produced more than 8 200 earthquakes by October 6, 2021. The quakes are occurring not far from the ongoing Fagradalsfjall eruption at depths between 5 and 7 km (3.1 to 4.3 miles) below the surface.
In 48 hours to 08:57 UTC on October 6, a total of 177 earthquakes have been detected in the area, 17 of them M2+ and 4 M3+.
14 earthquakes with magnitudes above 3 have been recorded since the start of the swarm, with the largest M4.2 at 15:32 UTC on October 2.
"They have been felt in the Reykjanes peninsula and in the southwestern part of Iceland," IMO said.1
The earthquakes could be a sign that magma is collecting below ground, but they are still far from the surface.
The Krýsuvík-Trölladyngja volcanic system is described by the Catalogue of Icelandic Volcanoes as an approximately 50 km (31 miles) long composite fissure swarm trending about N38°E, including a 30 km (18 miles) long swarm of fissures, with no central volcano.
It is one of the volcanic systems arranged en-echelon along the Reykjanes Peninsula west of Kleifarvatn lake.
The Fagradalsfjall and Krýsuvík fissure swarms are considered splits or secondary swarms of the Krýsuvík–Trölladyngja volcanic system.
Small shield volcanoes have produced a large portion of the erupted volume within the system.
Several eruptions have taken place since the settlement of Iceland, including the eruption of a large basaltic lava flow from the Ogmundargigar crater row around the 12th century.
The latest eruption, identified through tephrochronology, took place during the 14th century.2
1 IMO's Specialist Remark – October 5, 2021 at 16:42 UTC
2 Krýsuvík-Trölladyngja – Geological summary – GVP
Featured image credit: IMO
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