In a matter of weeks, the region surrounding the town of Grindavik went from experiencing regular seismic activity to three volcanic eruptions, the latest one happening just yesterday. The town was evacuated last November as quakes grew in number and intensity. Scientists could tell that a massive magma dike was forming underground, and new analysis shows just how powerful the forces beneath our feet can be.
The magma dike was estimated to have a length of 15 kilometers (9.3 miles), cracking the ground beneath the town and even threatening the famous Blue Lagoon, an open-air geothermal spa and major tourist destination. The dike was seen lengthening and rising, and researchers have now established the flow of magma into the dike. It was not just fast – they are calling it ultra-fast.
They have estimated that the flow rate was 7,400 cubic meters per second (261,328.5 cubic feet per second). That’s three Olympic swimming pools every second, or the concrete in the whole Three Gorge Dam every hour. It's an incredible flow rate. Certainly not there recently. Since 2021, there have been three eruptions in the Reykjanes Peninsula, where Grindavik is located. The flow rate of magma for those was 30 times lower than what has been witnessed this time.
Since the first eruption in December, scientists have been concerned that the new volcanic system would be bigger than the previous three combined – and they are being proven right. The January eruption reached the town of Grindavik, long since it had been evacuated. The new eruption began at 5:30 in the morning on February 8, in a location similar to the eruption of December 18, so further away from Grindavik.
Lava fountains were seen to be 50 to 80 meters (165 to 260 feet) tall with a plume reaching an altitude of 3 kilometers (slightly less than 2 miles). The Icelandic Meteorological Office reported the formation of tephra falls on Grindavik. Tephra is a frothy material that forms when lava cools quickly. The activity of the eruption is subduing and it is compared with what it was seen in December.
“A conspicuous, dark plume rises from one part of the eruptive fissure. This is likely due to magma interaction with groundwater which results in a slight explosive activity where white plume of steam mixes with dark volcanic plume,” the IMO staff reported. “It seems that tephra does not travel far from the eruptive fissure at the moment. The volcanic plume is dispersed towards south-west.”
The paper describing the motion of the magma is published in the journal Science.