Svartsengi: Ongoing Ground Uplift and Magma Accumulation

Low Seismic Activity in the Area of Unrest

November 19, 2024

Updated November 19 at 14:45 UTC

• Seismic activity remains low around the Sundhnúkar crater row.
• Ongoing uplift and magma accumulation beneath Svartsengi.
• Recent data interpretation suggests an eruption in November is unlikely.
• Hazard assessment remains unchanged.

Seismic activity around the Sundhnúkar crater row has stayed quiet, with only a handful of earthquakes picked up each day, mostly between Stóra-Skógfell and Sýlingarfell. Rough weather over the past week has caused problems for the seismic monitoring network, making it harder to catch smaller tremors.

Uplift and magma accumulation beneath Svartsengi are still going, though GPS measurements hint at a possible slowdown in recent days. It’s too early to read too much into that — similar fluctuations have turned up across the GPS network at stations well away from Svartsengi. Space weather and shifts in satellite orbits could also be nudging those readings.

New satellite images are expected next week, and they’ll make it possible to do a more meaningful comparison between the observed deformation and the GPS data.

Comparison graph of measurements from two GPS stations on the Reykjanes Peninsula, situated in Svartsengi and Herdísarvík. During the highlighted period, noted changes in deformation occur in both locations, which is considered unusual. Various factors, such as reference system anomalies, satellite movements, or solar activity, may account for minor systematic shifts unrelated to ground deformations.

Hazard Assessment Unchanged

Scientists at the Icelandic Meteorological Office (IMO) are still watching the situation closely. Their current read is that the pressure needed to trigger an eruption this November is unlikely to build up in time — a view backed by the area’s persistently low seismic activity. That said, any meaningful uptick in the uplift rate at Svartsengi or a clear rise in earthquakes would prompt a fresh look at that conclusion.

The IMO’s risk assessment stays in line with previous evaluations and is valid until November 26, assuming no significant developments in the meantime.

Updated November 12 at 17:45 UTC

• Seismic activity along the Sundhnúkur crater row is low.
• Ground uplift and magma accumulation persist beneath Svartsengi.
• The likelihood of an eruption this November is still considered low.
• The hazard assessment remains unchanged.

Things remain quiet along the Sundhnúkur crater row — very few earthquakes, and most of what has been recorded comes from between Stóra-Skógfell and Sýlingarfell. Weather has again been a factor, cutting into the monitoring system’s ability to detect smaller events.

Uplift and magma accumulation under Svartsengi are continuing along the same lines seen in recent weeks. The volume of magma needed to set off a new intrusion or eruption has been estimated at around 23 million cubic meters. At the current accumulation rate, that threshold could be reached by late November.

Looking at previous eruption patterns alongside current data, scientists think the chances of enough pressure building for an eruption this November are slim. That picture will shift if uplift rates at Svartsengi change.

Using Magma Accumulation and Seismic Activity to Assess Future Eruptions

In the weeks before each of the last two eruptions northwest of Grindavík, seismic activity climbed noticeably. That pattern is taken as a sign that pressure is rising in the magma chamber and that something significant may be getting close.

Data from previous eruptions and magma intrusions give scientists a better handle on how much magma is needed before the next major geological event beneath Svartsengi. There’s a defined window of elevated probability — bounded by lower and upper uncertainty thresholds — and tracking how seismic activity lines up with magma accumulation is a central part of that analysis.

If seismic activity picks up sharply while magma volumes are approaching critical levels, the probability of a new intrusion or eruption rises. That risk grows as more magma collects and quake activity intensifies. It’s worth keeping in mind that elevated eruption risk can persist for weeks before anything actually happens.

Updated November 8 at 18:00 UTC

• Low levels of seismic activity have been recorded in the Sundhnúkur crater row after the earthquake swarm on November 4.
• The volume of magma beneath Svartsengi is now roughly 80% of what was present prior to the last eruption that commenced on August 22.
• Additional webcams have been installed to enhance monitoring of eruptive fissures and lava flows.

In the early hours of November 4, some minor earthquake activity showed up in the Sundhnúkur area. Since then, seismic readings have been low — just a few small tremors after the swarm wrapped up. Strong winds during the period of adverse weather likely made it harder for the monitoring systems to catch everything.

Uplift and magma accumulation at Svartsengi are continuing. The total magma volume beneath the site now sits at around 80% of what was there before the eruption that began on August 22. If accumulation keeps pace, that level could start approaching pre-eruption thresholds before long. Even so, experts believe a higher total volume will be needed before the next intrusion is triggered.

Graph depicting magma accumulation and total estimated volume in the reservoir beneath Svartsengi since October 25, indicating current levels are about 80% of those before the eruption beginning August 22.

Enhancements in Monitoring Capabilities

The Icelandic Meteorological Office has put two new webcams in place at the northern and southern ends of the unrest zone — at Litla-Skógfell and Húsafjall respectively. Two more cameras are planned for installation soon. Together, these will give monitors a much clearer view of eruptive vents and lava flows if volcanic activity does break out, covering the full 9 km stretch of the Sundhnúkur crater row where fissures could open.

Updated November 4 at 18:30 UTC

• The earthquake swarm occurred in a region similar to previous magmatic intrusion sites.
• This seismic activity may indicate minor magma migration.
• No earthquakes have been logged since last night, with magma accumulation continuing.

Between 2 and 3 a.m. on November 4, a brief earthquake swarm hit between Sýlingarfell and Stóra-Skógfell, producing over twenty quakes at or below magnitude 1.0, at depths of 3 to 6 km. The area overlaps with where past magmatic intrusions have occurred. After the swarm ended, no further activity was recorded from 4 a.m. onward.

A map illustrating the earthquakes recorded between 2 and 4 a.m., showing dark red lines marking eruptive fissures active from December 2023 to August 2024. The lighter red line indicates the section of the fissure that remained active during the last eruption. A gray area highlights the lava flow extent from the eruption. These mappings utilize data from the Icelandic Institute of Natural History and the National Land Survey of Iceland.

No deformation signals came through from GPS stations or fiber optic networks, and there were no pressure fluctuations in the HS Orka boreholes at Svartsengi. In past cases where magma moved from Svartsengi toward the Sundhnúkur crater row, those instruments have shown clear responses.

One possible reading of the seismic activity is that magma migration may have started but stopped short of a significant intrusion. As of now, IMO instruments have not picked up any signs of increased magma accumulation beneath Svartsengi following the swarm.

Following standard emergency response protocols, the Icelandic Meteorological Office informed the Civil Protection Department about the earthquake swarm. Experts assessed whether a magma intrusion might be getting underway. With no additional signals detected, no further action was needed overnight.

Updated October 29 at 18:00 UTC

• Recent magma accumulation assessments suggest an increased likelihood for a new intrusion, possibly leading to an eruption by late November.
• Seismic activity remains minimal around the Sundhnúkur crater row.
• Hazard assessment unchanged.

Uplift and magma accumulation at Svartsengi have been ticking along steadily in recent weeks. Activity around the Sundhnúkur crater row has stayed low, with only a few small earthquakes recorded each day.

The Icelandic Meteorological Office has revised its estimate of how much magma needs to build up beneath Svartsengi before the next event. The updated assessment puts the probability of a new magma intrusion — and a possible eruption — rising toward late November. These figures are based on current deformation data and will be adjusted if uplift rates at Svartsengi change.

GPS measurements at the SENG station near Svartsengi from November 11, 2023, onward show shifts in north, east, and vertical measurements (top, middle, bottom). The lowest line details uplift in millimeters, with the previous day’s reading highlighted by a green dot. Red lines indicate the start of the last six eruptions (December 18, 2023; January 14, February 8, March 16, May 29, and August 22, 2024), while blue lines mark magma intrusions that did not result in eruptions (November 10, 2023, and March 2, 2024).

Monitoring Activity to Assess Future Events

In the run-up to each of the last two eruptions, seismic activity northwest of Grindavík climbed noticeably in the weeks before things kicked off. Scientists read that pattern as a sign of rising pressure in the magma chamber — a signal that the next event may not be far away.

Historical data from past eruptions helps with estimating how much more magma needs to gather beneath Svartsengi before triggering a future event. There’s a period of elevated probability for magma intrusion and potential eruptions, defined by bounding uncertainty thresholds. Watching how rising seismic activity maps onto magma accumulation is just as important as tracking the volume itself.

If a clear increase in seismic activity is recorded when magma volumes beneath Svartsengi are approaching critical levels, the likelihood of a fresh intrusion and possible eruption goes up. That probability grows incrementally as more magma accumulates and quake activity intensifies. Crucially, elevated eruption risk can persist for weeks before an actual event occurs.

Updated October 22 at 15:30 UTC

• GPS measurements and model calculations in the Svartsengi area indicate that ground uplift and magma accumulation are ongoing.
• If magma accumulation continues at the current rate, the lower uncertainty threshold for potential dike intrusion or eruption will be crossed by early November.
• The current hazard assessment will remain until October 29, barring significant changes.

Ground uplift and magma accumulation beneath Svartsengi are progressing much as they have in previous weeks. Seismic activity has ticked up slightly, with around five earthquakes recorded daily along the dike. The largest reached magnitude 1.5.

Model calculations suggest the volume of magma now sitting beneath Svartsengi is approximately two-thirds of what was recorded before the last eruption began on August 22.

If accumulation keeps up at a similar pace, the lower uncertainty threshold for new intrusions or eruptions is expected to be crossed in early November. A significant increase in seismic activity during that window could point to a growing likelihood of new magma intrusions. The probability rises with both greater magma accumulation and intensifying earthquake activity.

A graph showcasing magma accumulation progression and the estimated total volume beneath Svartsengi as of October 25 (red curve). Current magma volume is noted to be approximately two-thirds of that observed prior to the August 22 eruption (green curve).

Estimating Volumes through Model Calculations

Recent models put the magma accumulated beneath Svartsengi since the previous eruption ended at around 14 million cubic meters. The eruption that began on August 22 expelled an estimated 24 million cubic meters — the largest in this ongoing series. With an uncertainty of +/- 5 million cubic meters, the magma volume beneath Svartsengi will be approaching pre-eruption levels once it falls within the lower uncertainty limit of 19 million cubic meters and the upper threshold of 29 million cubic meters.

These models are updated continuously with GPS data and give a picture of how much magma has built up since the last intrusion, along with projections for when thresholds might be reached. Even small changes in the flow rate can shift the eruption risk assessment considerably. The historical pattern shows intervals between eruptions getting longer and the volume needed to trigger the next intrusion appearing to increase — which means elevated eruption probability can persist for a significant stretch before any event actually takes place.

Updated October 17 at 16:00 UTC

• Current measurements indicate roughly 4-5 weeks before a new eruption is considered likely.
• GPS measurements suggest continued inflation in the Svartsengi area.
• Warnings before an eruption can be remarkably brief, sometimes as short as 30 minutes.
• Seismicity remains low around the Sundhnúkur crater row.
• The hazard assessment remains unchanged.

Magma accumulation and ground uplift at Svartsengi have stayed on a consistent track in recent weeks. GPS data shows land uplift continuing at a steady pace, though it has eased off slightly over the past one or two weeks — not enough to suggest magma accumulation has stopped.

Ground movement at the GPS station SENG in Svartsengi since November 11, 2023, shown in the north, east, and vertical directions (top, middle, bottom). The bottom graph indicates vertical movements in millimeters, with the reading from yesterday (October 16) marked by a green point. Red lines denote the commencement of previous eruptions (December 18, 2023; January 14, February 8, March 16, May 29, and August 22, 2024). Blue lines illustrate dike movements that did not lead to eruptions (November 10, 2023, and March 2, 2024).

Data from previous dike movements and eruptions sharpens the picture of how much magma needs to accumulate beneath Svartsengi before the next event. Current models put the volume expelled during the last eruption at Sundhnúkur — which started on August 22 — at around 24 million cubic meters. Each subsequent dike movement or eruption in the series has required a comparable or greater volume than the one before it.

If accumulation continues at an adequate rate, the most likely outcome involves dike propagation and a possible eruption at the Sundhnúkur crater row. There’s still meaningful uncertainty around the timing, and monitoring efforts will keep a close eye on that as new data comes in.

Urgency of Timely Warnings Preceding Eruptions

The first signs that magma is on the move typically include a surge in earthquake activity, rapid changes in ground deformation, and pressure swings in boreholes. The gap between those first signals and the start of an eruption can be very short — before the most recent eruption on August 22, that window was just 30 minutes.

The current evaluation is based on the latest monitoring data from the Meteorological Office, and developments are being tracked closely. The timing of any future geological event remains uncertain, and shifts in magma accumulation rates will feed directly into future forecasts.

Seismic activity around the Sundhnúkur crater row continues, though at a lower level than in previous weeks. Earthquake activity west of Fagradalsfjall has also been quieter of late.

The IMO’s hazard assessment has been updated to reflect current conditions without change. Residents of Area 4 (Grindavík) remain at risk for sinkholes, with an assessment valid until October 29, barring further developments.

(Click on the map to enlarge it.)