The Icelandic Meteorological Office has reported an eruption on Mount Fagradalsfjall, part of the Krýsuvík-Trölladyngja Volcanic System, on the Reykjanes Peninsula, to the southwest of Reykjavik. The eruption began on Monday 10 July 2023, following about a week of intense seismic activity, with lava and smoke issuing from a fissure on one of the volcano's flanks. Small fissure eruptions of this kind are not unusual on Mount Fagradalsfjall, and the event is unlikely to cause any wider disruption.
The Krýsuvík-Trölladyngja Volcanic System comprises a composite fissure swarm about 50 km in length, with no central volcano, but several small shields (i.e. volcanic structures made up largely of overlapping lava deposits that resemble upturned bowls rather than a cone) including Mount Fagradalsfjall. The system was quiet for about 800 years before re-activating in 2021, since when small fissure eruptions of the type seen this week have happened several times.
Iceland lies directly upon the Mid-Atlantic Ridge, a chain of (mostly) submerged volcanoes running the length of the Atlantic Ocean along which the ocean is splitting apart, with new material forming at the fringes of the North American and European Plates beneath the sea (or, in Iceland, above it). The Atlantic is spreading at an average rate of 25 mm per year, with new seafloor being produced along the rift volcanically, i.e. by basaltic magma erupting from below. The ridge itself takes the form of a chain of volcanic mountains running the length of the ocean, fed by the upwelling of magma beneath the diverging plates. In places this produces volcanic activity above the waves, in the Azores, on Iceland and on Jan Mayen Island. All of this results in considerable Earth-movement beneath Iceland, where Earthquakes are a frequent event.
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