Iceland’s Reykjanes Peninsula Eruptions | Geldingadalir volcano, Meradalir, Litli-Hrútur, Hagafell, & Sundhnúkur | 2024
Friday, 23rd August 2024
Dominic Duff
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After more than 800 years, Iceland’s Reykjanes peninsula awoke to a new volcanic episode in 2021.
Effusive eruptions creating substantial lava flows have ushered in a new chapter in Iceland’s volcanic story, throwing up unique opportunities and challenges between people and nature. But with sensationalised headlines and multiple eruption sites, it’s easy to be confused about what’s happening with the recent eruptions on the peninsula.
This handy guide clarifies the timeline:
Geldingadalur Eruption: 19 March – 18 September 2021
Meradalir Eruption: 2 August – 21 August 2022
Litli-Hrútur Eruption: 10 July – 5 August 2023
Sundhnúkur Eruption: 18 December – 21 December 2023
Sundhnúkur (Hagafell) Eruption: 14 January – 16 January 2024
Sundhnúkur Eruption: 8 February – 9 February 2024
Sundhnúkur Eruption: 16 March – 8 May 2024
Sundhnúkur Eruption: 29 May – 22 June 2024
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
The Fagradalsfjall Volcano: Volcanic Activity begins
The Fagradalsfjall volcanic system, located 40 km southwest of Reykjavik, is part of the Reykjanes peninsula, a sparsely populated landscape of rugged terrain, lava fields, hot springs, and numerous Icelandic volcanoes. Here, the Eurasian and North American plates move laterally and apart, causing the crust to thin and form parallel fractures. This creates multiple volcanic systems, with Fagradalsfjall being one of six on the peninsula.
(Graphic courtesy of National Land Survey of Iceland)
The thin crust allows magma to rise, feeding the nearby Svartsengi Geothermal Power Plant. Unlike active volcanoes at destructive boundaries, these systems create volcanic events that erupt along fissures, forming multiple cones, as seen at Fagradalsfjall.
The volcanic eruptions here produce basaltic lava, which is less viscous, fast-flowing and releases minimal ash. The magma’s source is deep in the mantle, but it pools in small magma chambers of varying depths between 1 and 15 km, which dictate the seismic risks.
After 800 years of dormancy on the peninsula, Fagradalsfjall showed signs of activity in December 2019. Increased seismic activity and crustal deformation in January 2020 confirmed magma intrusion, signalling an imminent volcanic eruption, but the exact eruption site was still uncertain.
The Geldingadalur Eruption
Following nearly 40,000 earthquakes in the month prior, the first eruptive activity on the Reykjanes peninsula began at 20:45 local time on 19th March 2021.
19th March – 18th September 2021
- Duration: 184 days
- Maximum Effusion Rate: 20 m³/s
- Max Fissure Length: 970 m
- Lava Volume: 150,000,000 m³
- Area Covered: 4.25 km²
(Image credit: Porta – iStock)
The volcanic eruption took place in a remote location close to Geldingadalir valley, giving it its name. Reykjavik residents saw the sky illuminated by lava flows and thousands travelled to catch a glimpse of the show.
“This is a rather rugged area of Iceland with many centuries of historic lava flows dominating the landscape. This makes for challenging walking conditions on the hiking trail, but well worth the effort! The always resourceful Icelanders have done an amazing job in making it possible for their countrymen, and the odd foreign visitor like me, to enjoy the eruption site reasonably close. However, at this point, the pathways are fairly crude, and in places difficult to navigate, especially when darkness falls.”
Clive, founder of Discover the World Education, who visited the site in 2021
Spectating and Monitoring Volcanic Gases
The initial fissure eruption stretched for about 600-700 m and thanks to the eruption site being within a topographic bowl, the surrounding ridges provided the perfect viewing location.
Though these volcanic events are relatively safe from hazards like ash, lava bombs, and explosive episodes, high levels of volcanic gases such as sulphur dioxide caused the Icelandic Coast Guard to intervene and set up a strategy to manage the hiking trail and access to the eruption site. Air traffic was also put on alert.
Weather patterns and gas emissions were constantly monitored, and access was restricted to designated safe areas, car parks, and a hiking trail. Webcams monitored the eruption site through the night time, providing key updates on the first Fagradalsfjall eruption.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
Lava Flows and the Evolving Eruption
As the volcanic eruptions and lava flows continued, the initial fissure evolved into active vents in March with five additional smaller fissures opening up in April. By 2nd May, only Vent 5 near the initial eruption site at Geldingadalir remained active. The vent developed into a main cone, reaching 334 m above sea level.
Lava fountains from the main vent initially erupted continuously, growing to a height of 250 m by 28th April. These then switched to a cyclical pattern, with periodic pulsating eruptions reaching heights of 460 m, tall enough to be seen from Reykjavik.
The lava flow rate also increased to around 12.4 m³/s from 18th May to 2nd June, twice that of the first six weeks of the eruption.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
“The volcano itself is extremely beautiful and as darkness fell, the whole experience was extenuated. I walked down to the edge of the new lava to collect a few samples. In between the cracks I could see molten lava and the gases were quite intense, so I did not linger. The ground still shakes, and there is a constant murmur of the lava being expelled.”
Clive Stacey – Founder of Discover the World Education
Volcanic activity ended on 18th September, with the lava flows covering an area of 150 million m³ or 4.25 km². At 184 days, the Geldingadalir eruption site had seen the longest eruptive activity in Iceland in the 21st century, a title that it still holds.
The Meradalir Eruption
On 30th July 2022, an earthquake swarm was detected in the Geldingadalir valley, with thousands of small earthquakes occurring over the following days and the Icelandic Meteorological Office measured two at over 5 on the Richter scale. Deformation models also indicated the magma was just 1 km below the surface and a new eruption site was likely in early August.
3rd August – 21st August 2022
- Duration: 19 days
- Maximum Effusion Rate: 32 m³/s
- Max Fissure Length: 350 m
- Lava Volume: 12,000,000 m³
- Area Covered: 1.23 km²
On 3rd August 2022, a new eruption began at the Fagradalsfjall volcano. The fissure eruption was measured about 350 m long, and the lava flowed northwest at a rate of 32 m³/s before decreasing to an average of 18 m³/s. This was primarily flowing over the 2021 lava flows and filling the Meradalir valley, giving this eruption its name.
This fissure decreased in length forming a central cone with three vents at the eruption site by 10th August. Over the following week, the lava fountains decreased as the main cone grew, forming a suspended lava pond that fed further lava flows.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
By 21st August 2022, the eruption had ended having extruded around 12 million m³ of lava, creating flows around 20–40 m thick near the vent in the Geldingadalir valley, and 5–15 m thick down in the Meradalir valley.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
The Litli-Hrútur Eruption
The Reykjanes peninsula remained quiet from September 2022 to 4th July 2023, when an intense swarm of 12,000 earthquakes were recorded. On 10th July, a magnitude 5.2 earthquake saw lava breaking through the surface northeast of the previous eruption site near Litli-Hrútur.
10th July – 5th August 2023
- Duration: 27 days
- Maximum Effusion Rate: 50 m³/s
- Max Fissure Length: 500 m
- Lava Volume: 16,000,000 m³
- Area Covered: 1.48 km²
This volcanic eruption opened a fissure along a 1 km stretch of land, with an initial lava flow rate measured at 50 m³/s. This soon dropped to 13 m³/s as activity centralised around a 200 m fissure with intense lava fountains.
The active fissure quickly formed an elongated cone and lava pond that would periodically break, creating fresh lava flows that would travel south meeting the old lava flows from the Meradalir eruption. The crater rim collapsed on 19th and 24th of July, causing lava flows to travel to the east.
By 31st July 2023, the lava flow rate had decreased to 5 m³/s and from the surface it seemed that the eruption paused. Instead, the lava flowed beneath the surface from the eruption site, travelling under older flows.
This eruption stopped on 5th August, having extruded an estimated 16 million m³ of lava covering an area of 1.48 km².
This was also the final volcanic activity from the Fagradalsfjall volcanic system.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
The Sundhnúkur Eruptions – A Quick Guide
The Sundhnúkur Volcano is part of the Eldvörp–Svartsengi volcanic system, located on the Reykjanes peninsula in Iceland, about 30 km from Reykjavik.
This 7 km wide, 30 km long system lacks a typical volcanic cone or a central active volcano, and instead, eruption sites are dominated by fissures and clusters of volcanic cones or vents around a main crater area.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
It lies beneath the town of Grindavík, formerly home to 3,000 people, the Svartsengi Geothermal Power Plant and the Blue Lagoon, a world-famous geothermal pool popular amongst tourists, and an integral part of Iceland’s economy. This proximity to populated areas makes it one of the most hazardous of the Icelandic volcanoes.
The system has formed due to left-lateral shear along the mid-Atlantic ridge, where stretching and faulting create conditions for magma to rise and cause basaltic lava fissure eruptions.
(Image credit: Icelandic Meteorological Office)
Recent eruptions at Sundhnúkur have occurred along fault zones at the edge of a sinking rift valley, highlighted by the red and black lines in the map above.
The volcanic activity is influenced by magma accumulating in chambers and dykes 20–40 km deep, before rising and pooling just 1–5 km below the surface. As the land above uplifts under pressure, it eventually ruptures, leading to eruptions, followed by subsidence and eventual re-inflation before the next event.
Faults cutting through Grindavík contribute to significant seismic activity and tectonic hazards, making predicting eruptions challenging.
Warning times for Reykjanes eruptions have proven to vary from as little as 30 minutes to a week. This image highlights the land deformation that occurred on 18-19 November 2023, prior to the first eruption at Sundhnúkur.
(Image credit: Icelandic Meteorological Office)
Seismic Activity in Grindavík
On 24th October 2023, an intense earthquake swarm began in Grindavík as magma intruded beneath the town through a 15 km long dyke at an unprecedented rate of 7,400 m³/s- nearly 100 times higher than during the previous eruptions at Fagradalsfjall. By 9th November, land near Svartsengi rose by 5 cm, and seismic tremors peaked at 5.3 on the Richter scale.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
Over 20,000 earthquakes were recorded, accompanied by land deformation of up to 12 cm in 24 hours, causing widespread disruptions to utility services and severe damage to buildings, including homes, businesses, and the town’s sports centre. A new rift valley began forming outside the town, prompting an evacuation order on 10th November 2023.
Evacuation and Preparation
Scientists believed the next eruption site could potentially occur within the town. Residents relocated to shelters or stayed with family and friends as emergency teams secured utilities to prevent further damage.
Daily earthquakes declined but over a year later, 63 properties are deemed irreparable, with 523 cases under review by Iceland’s Natural Catastrophe Insurance, including 363 involving residential housing. Damages and protective measures are estimated at $580 million USD for 2023 and 2024, covering property compensation and levee construction to mitigate future risks.
18th December – 21st December 2023 (Sundhnúkagigar Crater Row)
- Duration: 2 days (47 hours)
- Maximum Effusion Rate: 400 m³/s
- Max Fissure Length: 3,169 m
- Lava Volume: 12,000,000 m³
- Area Covered: 3.73 km²
In December 2023, land under Svartsengi rose by 16cm as magma accumulated in a sill, culminating in an earthquake swarm near the Sundhnúkagigar crater row on 18th December. An hour later, a new effusive eruption started as a 3 km fissure erupted just 1.5 km from Grindavík, with spewing lava flowing eastward away from infrastructure and inhabited areas. As this was the first eruption from this volcanic system, the Coast Guard and air traffic were put on alert by the Icelandic Meteorological Office.
Over three days, multiple eruption vents formed around the eruption site, creating a 3.73 km² lava field. Initial flow rates of 100–200 m³/s peaked at 400–800 m³/s before tapering to 10 m³/s.
Scientists believed the lava’s complex composition suggested accumulation near the surface prior to eruption, potentially signalling a trend for future eruptions from this volcanic system.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
14th January – 16th January 2024 (Hagafell)
- Duration: <2 days (41 hours)
- Maximum Effusion Rate: 200 m³/s
- Max Fissure Length: 1,041 m
- Lava Volume: 3,000,000 m³
- Area Covered: 0.76 km²
On 14th January 2024, a new effusive eruption began as two fissures opened 1–2 km north of Grindavík. This volcanic eruption saw impressive lava fountains, with flowing lava threatening the town and its protective levees.
While the levees successfully stopped most of the lava, a small vent inside the barrier burnt down three homes on the town’s northern edge.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
The 41-hour eruption buried roads, damaged utility lines and created deep cracks descending 40 m to the groundwater level. Concerns grew over the southward trend of eruptions, raising fears of a future event directly beneath Grindavík, though this has not yet occurred.
8th February – 9th February 2024 (Sundhnúkagigar Crater Row)
- Duration: <2 days (31 hours)
- Maximum Effusion Rate: 600 m³/s
- Max Fissure Length: 1,961 m
- Lava Volume: 20,000,000 m³
- Area Covered: 4.24 km²
On 8th February 2024, an earthquake swarm near the Sundhnúkagigar crater row preceded a volcanic eruption from a 2 km fissure, sending lava plumes 50–80 m high. Though lasting only a few days, the eruption was larger than the December event, forming 2–3 craters. While lava flows avoided buildings and major infrastructure, they damaged the hot water pipe from the Svartsengi Power Plant, leaving 26,000 residents of the Reykjanes peninsula without heating or hot water.
16th March – 8th May 2024 (Sundhnúkagigar Crater Row)
- Duration: 54 days
- Maximum Effusion Rate: 1,215 m³/s
- Max Fissure Length: 2,773 m
- Lava Volume: 37,000,000 m³
- Area Covered: 6.18 km²
In March 2024, an earthquake swarm of 150 small tremors near the Sundhnúkagigar crater row signaled a dyke intrusion, facilitating the magma’s path to the surface. On 16th March, the volcanic eruption started creating a 2.5 km fissure that spewed lava in multiple directions before narrowing to 800–1,000 m over several days.
By 22nd March, five to seven craters had formed, consolidating into one main crater by 5th April.
(Image credit: Ragnar Th. Sigurdsson @ Artic Images)
Lava ponds within the crater rim periodically emptied, increasing lava flow rates, but these flows were contained by the levees protecting Grindavík.
An unfortunate casualty of this eruption was a gravel mine that was buried by lava on 21st March. The gravel from this mine was used to create protective barriers in the region.
29th May – 22nd June 2024 (Sundhnúkagigar Crater Row)
- Duration: 25 days
- Maximum Effusion Rate: 2,000 m³/s
- Max Fissure Length: 3,800 m
- Lava Volume: 45,000,000 m³
- Area Covered: 9.40 km²
On 29th May, a 3.8 km fissure opened at the Sundhnúkagigar crater row, marking the fourth volcanic eruption at the site. In the initial hours, lava flows peaked at 2,000 m³/s before slowing to 200–600 m³/s, with the fissure narrowing to 1–2.5 km as the eruption progressed.
Lava flows buried roads and caused electricity outages in Grindavík. At one point, lava topped the protective levees but was successfully stopped using jets of cold water, a technique last employed during the 1973 Eldfell eruption on Heimaey Island.
(Image credit: NASA Earth Observatory)
The image above, courtesy of the NASA Earth Observatory, clearly shows two active vents at the eruption site, with new lava travelling in three directions over previous lava flows. The defensive walls can be seen around Grindavík, the Blue Lagoon, and the Svartsengi Power Plant.
22nd August – 6th September 2024 (Sundhnúkagigar Crater Row)
- Duration: 16 days
- Maximum Effusion Rate: 2,000 m³/s
- Max Fissure Length: 5,650 m
- Lava Volume: 65,000,000 m³
- Area Covered: 16.16 km²
On 22nd August 2024, an earthquake swarm at the Sundhnúkagigar crater row preceded the fifth effusive eruption, with small quakes also detected 30 km away in the capital region, including one measuring 4.1 magnitude. A 4 km fissure erupted, later narrowing to 2 km north of Stóra Skógfell, followed by a second 1 km fissure.
Initial lava flows peaked at 2,000 m³/s before slowing in subsequent days. This marked the northernmost fissure on the Reykjanes peninsula, raising concerns about lava flows near a former US Army site with potential unexploded ordnance, posing risks to hikers venturing off of hiking trails and into restricted areas.
20th November – 8th December 2024 (Sundhnúkagigar Crater Row)
- Duration: 18 days
- Maximum Effusion Rate: 1,300 m³/s
- Max Fissure Length: 3,000 m
- Lava Volume: 50,000,000 m³
- Area Covered: 10 km²
On 20th November 2024, the tenth eruption began on the Reykjanes peninsula and the sixth from the Sundhnúkagigar crater row eruption site. This followed a 77-day gap from the last eruption—the longest between eruptions in the area.
This new fissure eruption quickly extended to 3 km northeast, with initial lava flow rates peaking at 1,300 m³/s before decreasing to 7–8 m³/s after eight days. Lava buried the Blue Lagoon’s main parking area and flowed over the main road to Grindavík, while severed power lines caused electricity outages.
This recent eruption marked the furthest westward lava flow, aided by a narrow channel from the previous eruption. Water cannons were deployed along the Svartsengi levees and near electrical infrastructure to cool the lava and prevent further damage. The eruption ended on 8th December 2024, when the final glow was detected in the crater, signalling the end of any visible activity.
Free Classroom Resource
The eruption activity across the Reykjanes peninsula is an evolving case study for the Geography classroom. Download our free image bank resource to deepen your students’ understanding of tectonic hazards and the awe-inspiring power of volcanism.
