Iceland’s 2024 volcanic eruptions—threats to Grindavik and Blue Lagoon
March 4, 2025
In my last post, I described the flows that emitted from the Fagradalsfjall fissure during the 2012-23 eruptions that heralded a new period of active volcanism in the Reykjanes Volcanic Belt: https://landscapes-revealed.net/return-to-iceland-viewing-lava-from-the-2021-23-eruptions/. At the end of 2023, volcanic eruptions began in a new place. They continued until the end of 2024, and will likely continue in 2025.
Background about the 2024 Sundhnúkur eruptions
In December 2023, volcanism resumed, but this time along a northeast–southwest fissure located west of Fagradelsfjall (see map below). So far, there have been seven eruptions, the last one in December 2024. Eruptions followed an intense series of earthquakes in November 2023 that were caused by magma moving underground.
This satellite map (from Apple Maps) shows the lava (black areas) that erupted on the Reykjanes Peninsula between 2021 and 2024. In my last post, I described a hike we did along the ridge west of the Fagradelsfjall eruptions. The newer 2023–2024 eruptions are on the next fissure west of Fagradelsfjall; they are named for Sundhnúkur, the highest point in the crater chain along this fissure. I’ll refer to the annotated locations in the photos below.This graph shows vertical displacement of the land near the eruption centers during the seven eruptions from December 2023 to December 2024. The land lifted “Up” before each eruption, as magma flowed into the area. During the eruption, the magma flowed out (then called lava) and the land abruptly sank. The data in this graph ends in December 2024, but the land has continued to rise since then.
The figure above is from the Iceland Meteorological Office web site— https://en.vedur.is/about-imo/news/eruption-begins-on-the-sundhnukur-fissure-swarm—where you can find more information about the eruptions. For example, there is a map that shows the first six eruptions in purple and the last eruption—the one that impacted the Blue Lagoon—in yellow/red. It also shows the duration and volume of the seven eruptions. The first three were short and small; the last four were longer and much more voluminous. Refer to the map above. I took this photo while on Highway 43, heading north from Grindavik. The view is eastward toward the black-colored lava field. Unlike the Fagradelsfjall eruptions, the 2023–24 eruptions were not confined to a valley but were able to spread out more widely. Nevertheless they are thick enough to be cooling slowly, with enough heat remaining to melt overlying snow.
Photos from Grindavik
If you examine the map above, you will see two red circles near Grindavik. When clicking on these circles, I got a message that the road was closed and that the area was hazardous because of a probable impending eruption. We were coming from the west and found the road open, but we encountered a town where a great deal of infrastructure had been built to cope with last year’s eruptions.
Highway 43 just north of Grindavik had been covered with lava and a new road (labeled with white arrow) had been built on another part of the new lava flow. A high berm had been built all around the town to protect it from impending flows. The berm was built of crushed lava rock (they have lots!) and appears to have been largely effective.
I took this photo from on top of the berm that extends along the western edge of Grindavik. I was standing at a location very close to the northernmost red circle on the map above. You can see from the map that the lava flowed right up to the edge of the berm. The view is southward, with the ocean in the background. The highway at this location is between the town and the berm.This view of the new lava is toward the southwest and is located just west of the berm in the previous photo—it’s the edge of the black lava just north of the northernmost red circle on the map above. The yellow box outlines Jay’s yellow jacket for scale. This new lava was very jagged and sharp.This photo is a wider view of the area in the photo above. I’m standing on the new part of Highway 43 (see map above) where it heads west from where the old road got covered by lava. It appeared that they chose to swing the new road westward and then northward so that they could extend the berm across the old road and protect the town from the southward-moving lava flow. I took this photo on the new part of Highway 43 where it swings northward toward the Blue Lagoon. The 2024 lava here is thin enough to have cooled and the snow had not melted. These flows occurred in the earlier part of 2024.We saw many workers in trucks and bulldozers who were still moving rocks around to extend and heighten the berms, in anticipation of future eruptions. In town, things seemed pretty normal. Grindavik is an important fishing harbor and we saw large containers of fish being offloaded. It seemed like a good idea to sample their wares—we found some of the best fish and chips we’ve ever had at Papa’s Restaurant.
Photos from the Blue Lagoon
The last eruption in 2024, from November 20 to December 9, caused lava to flow westward toward the Blue Lagoon (see map above). This is one of Iceland’s most popular tourist spots and the government went all out to protect it. I had visited this site in 2022 and was amazed by how different it looked in 2025. I find it a highly-commercial hot pool that is not worth the time or money, given all of the amazing places Iceland has to soak in hot water. But it is close to the airport and Reykjavik and it is packed with visitors.
This is a view, looking west, of the Blue Lagoon. There is a new rock berm that was built in front of the building to protect it and the part of the lagoon on the other side of the berm where people soak. On the left side of the photo is an important geothermal power plant that supplies energy and hot water to the Reykjanes Peninsula. It is affluent from the power plant that flooded this low-lying area and created the pools that people now enjoy.I took this photo on the west side of the lagoon—see blue water near right side of photo. I am standing where lava is covering the area where the parking lot used to be. Notice the rock berm along the left side of the photo—this berm extends far into the distance, around to where it connects to Highway 43. Look at the map above to see the berm, which extends along the west and north side of the lagoon. This was an expensive endeavor, but clearly the berm kept the lava from flowing closer to the lagoon. I took this photo near Highway 43, where lava covered the former entrance road to the Blue Lagoon. A whole new entry road was created a little south of the old road (see map above). Steam rising from the lava indicates it is still hot and can melt overlying snow.I took this photo on the part of Highway 43 that was newly constructed on top of the fresh lava. On the map above, it is where the black lava crosses Highway 43. This lava is still black because it is thick and has not yet cooled so it melts the snow. We saw steam rise from the lava as we drove past. The yellow sign says “hazardous”. The road was rough from the still unstable lava.
Updated 4 March. “Deformation measurements indicate that land uplift continues at a similar rate as in recent weeks. The amount of magma beneath Svartsengi [in fissure zone] is now greater than what was estimated before the eruption that began on November 20, 2024. The likelihood of magma intrusion and an eruption is increasing, and all indications suggest that this could happen within the coming days or weeks.”
Look at the graph beneath the map above. The red line since the December 2024 eruption is now as long as the line before the end of December 2023 eruption, indicating that magma has moved upward and uplifted the land to the point where another eruption is likely. It could happen before we leave Iceland on March 17—stay tuned!
Hey guys! Another interesting post from our favorite traveling geologists. Fascinating. I saw actual lava once visiting Mauna Loa in Hawaii… but under very different weather conditions! Stay warm and Happy Birthday to Jay!
Landscapes Revealedon March 5, 2025 at 11:57 am
Thanks Mark! Hawaii is an easier place to stand around and watch lava flow! Although you don’t have the possibility of seeing the Northern Lights there…
Julieon March 5, 2025 at 10:08 am
I hope you get the chance to experience an eruption. We did on the island of Réunion and it was beautiful – although it made us reroute our trip around the island a bit as the lava had gone over the main road that runs near the coast. We were just chilling in the pool at this little hotel in Saint-Philippe and around sundown we noticed this reddish light on the horizon. So out of the pool and into the rental car. Got pretty close, enough so that we got a bit nervous when the car refused to start when we figured we should leave – until about the 10th try!
Hey guys! Another interesting post from our favorite traveling geologists. Fascinating. I saw actual lava once visiting Mauna Loa in Hawaii… but under very different weather conditions! Stay warm and Happy Birthday to Jay!
Thanks Mark! Hawaii is an easier place to stand around and watch lava flow! Although you don’t have the possibility of seeing the Northern Lights there…
I hope you get the chance to experience an eruption. We did on the island of Réunion and it was beautiful – although it made us reroute our trip around the island a bit as the lava had gone over the main road that runs near the coast. We were just chilling in the pool at this little hotel in Saint-Philippe and around sundown we noticed this reddish light on the horizon. So out of the pool and into the rental car. Got pretty close, enough so that we got a bit nervous when the car refused to start when we figured we should leave – until about the 10th try!
Yikes! But you got to see it – good story!