Iceland’s spectacular volcanic eruption could be the start of 300 years of sustained activity. Six volcanic regions vibrate together in a rhythm of 1000 years.
The long-awaited volcanic eruption on Iceland’s Reykjanes Peninsula in southwest Iceland began shortly after 10:00 p.m. local time on December 18th. Lava fountains erupted from an eruptive fissure and expanded over the course of the night to a length of about four kilometers, with molten rock flowing across the landscape on both sides of the fissure.
This means that the eruption fissure is already significantly longer than in the 2021 and 2022 eruptions, when the cracks only measured a few hundred meters each. Its southern end has approached the city of Grindavik to about three kilometers. The approximately 3,600 residents had to leave the town on November 10th because there were signs of an impending volcanic eruption.
According to the Icelandic Meteorological Service, Grindavik is currently not threatened by lava. In addition, the volcanic fissure is less than two kilometers from the Svartsengi hydrothermal power plant and the Blue Lagoon tourist attraction, although there is a mountain range in between.
According to Icelandic media reports, most of the molten rock is currently flowing east toward uninhabited land; In the north, police and emergency services are completing the construction of a protective wall to keep lava away from the access road to Svartsengi and Grindavik. Volcanic gases and ash are also carried out of cities by the wind. According to the Icelandic airline Icelandair’s website, the outbreak does not threaten flight operations at nearby Keflavik Airport.
Since late October, earthquakes and ground movements in the Grindavik region suggested that a mass of underground molten rock was moving from the northeast toward the city. This supposed intrusion is also the origin of the current volcanic eruption. At the start of the eruption, it was estimated that up to 200 cubic meters of lava per second was pouring out of the fissure, equivalent to about 1,600 bags of trash.
Since then, volcanic activity has calmed down somewhat. However, this does not mean that the eruption is already subsiding, writes the Icelandic Meteorological Service. An equilibrium has simply been established, a process that could already be observed in the outbreaks of previous years. The spectacular eruptions along the entire fissure, which were seen in videos of the eruption, are also unlikely to last long. As the eruption progresses, volcanic activity is likely to concentrate in one or two centers, as the course of eruptions in previous years suggests.
A new cycle of activity
Although the Grindavik volcanic eruption does not pose a threat in itself, it is another indication of potentially worrying developments. After 800 years of relative calm, the volcanic areas of the Reykjanes Peninsula appear to be awakening. And they follow a different rhythm than most other Icelandic volcanoes: over decades and centuries, they repeatedly create fissure volcanoes that spew lava and ash. The reason for this unusual behavior is that an underwater ridge meets Iceland on the Reykjanes Peninsula.
Iceland lies exactly at the intersection of two major parts of the Earth’s crust: the North American Plate and the Eurasian Plate. Both separate in an east-west direction. On the border between the two is an elongated underwater volcanic ridge made of molten rock that continually rises to fill the gap between the plates. This Reykjanes Ridge connects Iceland to the peninsula and the once simple plate boundary becomes complicated.
From here, a wide volcanic belt stretches northeast across the island. However, directly to the east lies the seismic zone of southern Iceland, an area in which the two tectonic plates slide past each other almost parallel. The Reykjanes Peninsula is, so to speak, the junction of these different forms of boundary between the earth’s plates. Due to this peculiarity, it consists of six long volcanic zones that run parallel to each other from southwest to northeast across the peninsula. The six volcanic zones of the Reykjanes Peninsula have almost always been active together over the past millennia.
Now it seems to be happening again. With the Grindavik eruption, another volcanic zone reappears. In March 2021, the Fagradalsfjall volcano, which is part of the volcanic area of the same name, erupted for the first time. Further eruptions in Fagradalsfjall followed in August 2022 and July 2023, but the current eruption is taking place in the Eldvörp-Svartsengi area, another volcanic strip west of the Fagradalsfjall area.
This corresponds to the historical pattern. After breaks of up to 1,000 years, the volcanic zones appear to awaken together and repeatedly cause productive eruptions over a period of around 300 years. This last happened between the 10th and 13th centuries, when sporadic eruptions from fissures up to ten kilometers long occurred in Reykjanes. The last series of eruptions in this phase, from 1210 to 1240, produced lava flows that covered about 50 square kilometers. The new eruptions could be a harbinger of another 300 years of volcanic unrest just a few dozen kilometers from the capital Reykjavík.