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 remained relatively muted, with only a handful of earthquakes detected daily, primarily between Stóra-Skógfell and Sýlingarfell. Inclement weather in the past week has hampered the seismic monitoring system, impacting its ability to detect smaller tremors.

Uplift and magma accumulation beneath Svartsengi are ongoing, although GPS measurements indicate a potential slowdown in recent days. It is premature to draw definitive conclusions regarding the magma inflow rate, as similar fluctuations have been observed across the GPS network at locations far from Svartsengi. External factors, including space weather and orbital shifts of satellites, may also be influencing these readings.

As new satellite images become available next week, they will allow for a more thorough comparison between the observed deformation and 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) continue to assess the likelihood of imminent volcanic activity. Current evaluations suggest that the pressure needed for an eruption this November is unlikely to accumulate, a conclusion supported by the area’s ongoing low seismic activity. Any significant shifts in the uplift rate at Svartsengi or a notable increase in seismic events may prompt a reevaluation of this assessment.

The IMO has issued a risk assessment that remains consistent with previous evaluations, valid until November 26. This remains contingent on continued monitoring for any noteworthy developments.

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.

Seismic activity remains subdued along the Sundhnúkur crater row, with minimal earthquake frequency. Most of the recorded earthquakes have occurred between Stóra-Skógfell and Sýlingarfell. Weather conditions have further reduced the seismic monitoring system’s ability to detect small seismic events.

Ongoing uplift and magma accumulation under Svartsengi are tracking the established trends of recent weeks. The volume of magma necessary for triggering a new intrusion or eruption has been estimated at approximately 23 million cubic meters. Should magma continue to accumulate at the current rate, this threshold could be reached by late November.

Recent analyses suggest, based on prior eruption patterns and current data, that the likelihood of sufficient pressure buildup leading to an eruption in November is slim. Any changes in uplift rates at Svartsengi will alter this assessment moving forward.

Using Magma Accumulation and Seismic Activity to Assess Future Eruptions

Historically, the weeks preceding the last two eruptions in the area northwest of Grindavík have been marked by increasing seismic activity. This pattern is interpreted to signal that pressure is building within the magma chamber, suggesting that the next event may be imminent.

Data gleaned from previous eruptions and magma intrusions allow scientists to better estimate the volume of magma needed for the next significant geological event under Svartsengi. A defined timeframe marks the increased likelihood of magma intrusion and potential eruption, bounded by lower and upper uncertainty thresholds. Monitoring how seismic activity correlates with magma accumulation is equally essential.

If a marked rise in seismic activity occurs while magma volumes reach critical thresholds, the chances of a new intrusion or eruption will increase. This probability will escalate as more magma collects and seismic activity intensifies. It is worth noting that the risk for an eruption may remain elevated for weeks before the occurrence of a significant geological event.

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, minor earthquake activity was documented in the Sundhnúkur area. Since then, seismic readings have remained low, with only a few small tremors detected in the aftermath of the swarm. Adverse weather conditions, particularly strong winds, likely hampered the detection capabilities of the monitoring systems.

Uplift and magma accumulation are ongoing in Svartsengi. The total magma volume beneath the site currently stands at around 80% of the volume observed before the eruption that began on August 22. If the accumulation rate persists, this level could soon align with pre-eruption thresholds. However, experts agree that a higher volume of magma will be necessary to instigate the next intrusion.

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 recently deployed two new webcams at both the northern and southern endpoints of the unrest zone, situated at Litla-Skógfell and Húsafjall, respectively. Plans are in motion to install two additional cameras shortly. These innovations will significantly improve monitors’ capability concerning eruptive vents and lava flows in the event of volcanic activity, particularly across the 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, yielding over twenty quakes around or below a magnitude of 1.0 at depths of 3 to 6 km. This activity is concentrated near areas where past magmatic intrusions have been noted. Following the swarm’s conclusion, no further activity has been observed since 4 a.m. that morning.

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 were detected by GPS stations or fiber optic networks, nor were there pressure fluctuations in the HS Orka boreholes located in Svartsengi. Historically, when magma has transitioned from Svartsengi to the Sundhnúkur crater row, these monitoring instruments have shown clear indicators.

A possible interpretation of the recent seismic activity is that magma migration may have commenced but halted before significant intrusion occurred. Currently, no signs of increased magma accumulation beneath Svartsengi have been observed by IMO instruments post-earthquake swarm.

In accordance with standard emergency response protocols, the Icelandic Meteorological Office apprised the Civil Protection Department regarding the earthquake swarm. Experts will evaluate the possibility of a magma intrusion’s initiation. Since no additional indicators have been detected, no further action has been necessitated 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 continued steadily in recent weeks. The activity around the Sundhnúkur crater row has been low, with only a few small earthquakes recorded daily.

The Icelandic Meteorological Office has updated its evaluation of the magma volume necessary beneath Svartsengi to trigger the next event. This revised assessment indicates that the probability of a new magma intrusion—and potentially an eruption—increases toward late November. These estimates rely on currently available deformation data. Any changes in uplift rates at Svartsengi will adjust this assessment as necessary.

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

Leading up to the last two eruptions, seismic activity northwest of Grindavík has peaked weeks before eruptions began. Such inclusions signal rising pressure levels in the magma chamber, suggesting the next event could be on the horizon.

Historical data from previous eruptions assists in estimating how much additional magma must gather beneath Svartsengi to trigger a future event. A period marked by increased likelihood for magma intrusion and potential eruptions is characterized by bounding uncertainty thresholds. It is equally vital to monitor the synchronization of rising seismic activity along with magma accumulation.

A notable rise in seismic activity — if recorded when magma volumes beneath Svartsengi reach critical levels — will increase the likelihood of fresh intrusion and possible eruption. That probability will incrementally grow with additional magma accumulation signals. Crucially, the risk of an eruption may remain elevated 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 consistently with previous weeks. Recent seismic activity has slightly increased with around five earthquakes recorded daily along the dike. The most significant earthquake reached a magnitude of 1.5.

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

If magma continues to accumulate at a comparable pace, the lower uncertainty threshold needed to nurture new intrusions or eruptions is anticipated to be reached in early November. Should a significant increase in seismic activity occur during this period, it may imply an escalating likelihood of new magma intrusions and potential ruptures. Likelihood gradually rises with both increased magma accumulation and intensifying seismic 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 estimate that around 14 million cubic meters of magma have accumulated beneath Svartsengi since the previous eruption concluded. The last eruption, which began on August 22, had an estimated volume of approximately 24 million cubic meters, marking it the largest in this ongoing series of events. With a calculated uncertainty of +/- 5 million cubic meters, the volume beneath Svartsengi is likely to reach levels comparable to its pre-eruption state once it falls within the bounds of the lower uncertainty limit (19 million cubic meters) and the upper threshold (29 million cubic meters).

These models, continually updated with GPS data, provide insights into how much magma has accumulated since the last intrusion, offering projections for when thresholds may be attained. It’s important to note that even minor changes in the flow can significantly shift assessments regarding eruption risks. The historical pattern indicates that intervals between eruptions are lengthening, and the volume required to incite the next intrusion appears to be on the rise, suggesting that eruption probabilities may be perceived as heightened for considerable periods prior to any events.

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.

Trends in magma accumulation beneath and ground uplift above Svartsengi have stayed consistent in recent weeks. GPS data indicates that land uplift continues at a steady pace and has reduced slightly over the past one or two weeks without indicating a cessation in magma accumulation.

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).

Insights from prior dike movements and eruptions enhance understanding of how much magma must amass underneath Svartsengi before the next event occurs. Current models suggest that around 24 million cubic meters of magma were expelled during the last eruption at Sundhnúkur, which commenced on August 22. Each subsequent dike movement or eruption thus far has required a comparable or greater volume of magma accumulation than earlier events.

If magma accumulation continues at a suitable rate, the most probable outcome hinges on dike propagation and potentially, an eruption at the Sundhnúkur crater row. However, significant uncertainty remains regarding the timing of the next event. Monitoring efforts will focus closely on assessing the time to the next event as more data becomes available.

Urgency of Timely Warnings Preceding Eruptions

The initial signs of magma movement typically entail an increase in earthquakes, swift changes in ground deformation, and pressure variations in boreholes. The interval between the first signals and the potential onset of an eruption can be remarkably short; for example, only 30 minutes elapsed before the most recent eruption on August 22.

The current evaluation is grounded in the latest monitoring data from the Meteorological Office, with ongoing developments under vigilant scrutiny. The timing of any impending geological events remains uncertain, with changes in magma accumulation rates likely to impact future forecasts.

Seismic activity persists around the Sundhnúkur crater row, although with fewer events reported than in previous weeks. Recent weeks have also seen diminished earthquake activity west of Fagradalsfjall.

The IMO’s hazard assessment has been updated to reflect ongoing 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.)