Town of Grindavik evacuated again as new eruption begins on the Reykjanes Peninsula, Iceland.

Eruptive activity on the Reykjanes Peninsula, Iceland began again on 29 May 2024, according to the Icelandic Met Office, the first such eruption since activity on a fissure which opened in March petered out three weeks ago. The activity is thought to have started when magma flowing from the magma reservoir beneath Svartsengi into the area beneath the Sundhnúkur crater row. At about 4.00 pm on 29 May the magma encountered groundwater penetrating through a fissure from a previous eruption, leading to a phreatic explosion as a large volume of the water was turned into steam instantly. This led to the formation of a new fissure running southwest to northeast (parallel to previous fissures on the peninsula) for about 2.4 km. This fissure has produced lava fountains up to 50 m high, and is extruding lava at a rate of about 1500-2000 m³ per second. The eruption has prompted the evacuation of the town of Grindavik, and the nearby Blue Lagoon Geothermal Spa. The fissure is further from the town than the eruption in January which saw lava entering the streets of the settlement and several buildings destroyed, but is also significantly larger, and is evolving significant amounts of toxic gasses.

A volcanic fssure on the Reykjanes Peninsula, Iceland, which opened on 29 May 2024. Marco Di Marco/AP.

Although dramatic, lava flows are not usually considered particularly dangerous, as their advancing fronts are quite slow and can quickly be outpaced by an able-bodied Human being. The more deadly volcanic events are pyroclastic flows, such as the one which engulphed the Roman town of Pompeii, in which clouds of superheated gas and ash move downhill at high speeds in an avalanche-like motion, and phreatic explosions, caused by bodies of lava encountering bodies of water, which evaporate almost instantly, causing huge explosions.

The size and position of the new fissure on the Reykjanes Peninsula, Iceland. Icelandic Met Office/BBC.

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.

The passage of the Mid-Atlantic Ridge beneath Iceland. NOAA National Geophysical Data Center.

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Eruption on Mount Fagradalsfjall, Iceland.

The Icelandic Meteorological Office has reported an eruption on Mount Fagradalsfjall, part of the Krýsuvík-Trölladyngja Volcanic System, on the Reykjanes Peninsula. The eruption started at about 8.45 pm local time on Friday 19 March 2021, with a fissure 500-700 m in length opening up to the southeast of the main volcano, and produced lava fountains up to about 100 m high, with the lava spreading to cover an area of about 1 km² by the next day. The eruption persisted for several days, but decreased in intensity steadily. While spectacular, the eruption was not particularly dangerous, attracting large crowds of onlookers, some of whom took the opportunity to cook sausages on the cooling lava.

 

Crowds of onlookers watch a fissure eruption to the southeast of Mount Fagradalsfjall on the Reykjanes Peninsula, Iceland. AFP/Getty Images.

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 has been essentially quiet for about 800 years, with the last known eruption happening in the fourteenth century, and the last major eruption two centuries before that. However, an eruption in the area was expected, as a very large number (over 50 000) of earthquakes had been recorded beneath the system over the past few weeks, something which is often indicative of fresh magma moving into chambers beneath inactive volcanoes.

 

Earthquakes with a Magnitude of 4.0 or greater on the Reykjanes Peninsula over the past 30 days. USGS.

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.

 

The passage of the Mid-Atlantic Ridge beneath Iceland. NOAA National Geophysical Data Center.

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