Eruption Continues at Sundhnúkur Crater Row

Ongoing Uplift at Svartsengi – Hazard Assessment Remains Unchanged – Map Valid Until 31 July 2025

15.7.2025

Updated at 11:30, 20 July 2025

Recent eruptions at the Sundhnúkur crater row have resulted in notable air pollution. Volcanic haze has blanketed much of the area, though it has not been entirely captured by the national air quality monitoring network. According to the Icelandic Meteorological Office, gas emissions are expected to persist in South and West Iceland, compounded by light winds that are likely to maintain a haze over the southwest. Vulnerable residents are urged to minimize outdoor activities during this period of discomfort, and guidelines for reducing indoor exposure are available.

As of 15 July 2025, ongoing data indicates a slight decrease in the rate of uplift at Svartsengi, although the trend continues. The figures reveal that approximately two-thirds of the magma withdrawn from its chamber during the seismic activity on 1 April has now reaccumulated. If this accumulation rate holds steady, the chances of a magma intrusion or eruption may rise as autumn draws near.

Recent seismic activity has shown an uptick in both the Sundhnúkur area and near Fagradalsfjall, with activity slightly intensifying in recent weeks.

The hazard assessment for Svartsengi remains unchanged and is valid until 29 July 2025, with updates scheduled for that date. In the event of significant changes, the hazard assessment will be revised accordingly.

The accompanying hazard map outlines the current dangers in Svartsengi, highlighting both ongoing threats and potential risks should volcanic activity persist.

Update 1. July

• Uplift and seismic activity in the Svartsengi area remain stable.

• Magma continues to accumulate in the subterranean reservoir beneath Svartsengi.

• No substantial changes necessitate a revision of the current hazard assessment.

• Should magma accumulation persist, the likelihood of an intrusion or eruption will increase.

• The Icelandic Meteorological Office’s hazard map is valid until 15 July 2025, unless conditions change.

The Svartsengi region continues to experience land uplift and seismic activity, with activity levels stabilizing over recent weeks. An average of ten micro-earthquakes are detected daily, predominantly occurring north of Grindavík and south of Stóra Skógfell.

No significant changes in key measurements warrant a reassessment of the hazard level. However, continued magma accumulation could heighten the risk of a magma intrusion or volcanic eruption in the upcoming autumn.

Update 18. June

Ground Deformation (GPS Data)

GPS measurements indicate that uplift at Svartsengi continues, albeit at a reduced rate in recent weeks. Scientists at the Icelandic Meteorological Office suggest that if magma accumulation persists, the probability of a magma intrusion or eruption will escalate in the autumn months. A volume of magma comparable to previous events is believed necessary for an eruption to occur.

Image 1: Magma Accumulation under Svartsengi from October 2023 to June 2025

This image illustrates the estimated magma volume changes in the crust at Svartsengi, with each color representing distinct periods of magma activity. While magma accumulation appears steady week to week, the inflow rate gradually diminishes over time.

Image 2: GPS Measurements from Svartsengi (SENG)

The data showcases deformation in north (top image), east (middle image), and vertical (bottom image) directions from November 2023 to June 17, 2025. While uplift persists (illustrated in the bottom image), its pace has slowed in recent weeks. Red lines mark significant events such as magma intrusions and eruptions. The current uplift rate has seen a reduction recently.

Image 3: GPS Measurements from Fagridalur (FAGD)

This data reflects movement and deformation at the GPS station FAGD, located west of Fagradalsfjall. It shows northward, eastward, and vertical movements. Established during the summer of 2024, the data does not extend further back in time. Blue lines denote intrusions without associated eruptions. Red lines indicate eruptions. The intrusion on April 1 occurred just west of this station, spurring notable southeastward shifts as the magma intruded.

Although the April 1, 2025 eruption was modest in terms of lava output, it was still significant. The main phase involved a magma intrusion moving north, extending further than the earlier event on November 10, 2023, which predominantly flowed southward beneath Grindavík. This latest activity marks the second largest in the Sundhnúkur series, trailing only the November 10 event.

Deformation Pattern During Magma Intrusions

The deformation recorded during magma intrusions is characterized by the formation of a graben above the intrusion site, with the crust on either side moving outward and upward. Concurrently, subsidence is observed in Svartsengi as magma exits the chamber and flows into the dike.

Measurements near Svartsengi reflect this duality, with visible subsidence at the SENG GPS station, albeit less pronounced than the effects of the dike formation. In modeling magma accumulation beneath Svartsengi, adjustments must be made for the deformation due to dike formation. Consequently, the uplift around Svartsengi has returned to pre-April 1 levels, even as only slightly more than half of the magma volume that exited the chamber has since been replenished (refer to Image 1).

Earthquake Activity

Seismic activity remains steady, averaging about ten micro-earthquakes daily. Most activity centers just north of Grindavík.

Hazard Map

The hazard map has been revised and will remain in effect until 15 July 2025. While largely similar to its predecessor, a few noteworthy updates can be highlighted.

Image 4: IMO’s Hazard Map

The area between Vogaheiði and Fagradals-Hagafell is now classified as low hazard, down from a previous moderate designation. This adjustment results from a reassessment of the eruptive fissure risk, now deemed lower than before. Similar revisions apply to the southwestern end of Zone A (Grindavík). For further details on the reassessment process, please refer to this link.

Now, sinkhole hazards are recognized as a potential threat in Zone C (Vogar). This change stems from a previous oversight regarding fractures that emerged during the last eruption on 1 April. The magmatic dike extended farther northeast than previously noted, but minor fractures in the southeastern corner of this area went unreported until a thorough review highlighted their presence.

Crucially, the hazard map aims to convey immediate risks and potential threats associated with ongoing volcanic unrest in the Svartsengi system.

Update 3. June

• Uplift at Svartsengi continues.

• Based on the recent magma accumulation rates, the likelihood of a new eruption is anticipated to grow as autumn approaches.

• Seismic activity near the dike continues to decline.

• The hazard assessment remains unchanged and is valid until June 18, barring any significant changes.

Uplift and magma accumulation persist beneath Svartsengi, though rates have diminished when compared to earlier periods. As conditions refine and evolve, the likelihood of magma intrusion or eruption is projected to increase heading into the autumn months.

Recently, the area has experienced between ten and twenty small earthquakes per day around the dike from the April 1 eruption, though seismic activity has been on a steady decline. Most earthquakes cluster in two regions: one in the southern portion of the dike near Grindavík, and another between Sundhnúkur and Stóra Skógfell. Occasionally, tremors can still be detected near the northern end of the dike, north of Keilir.

The hazard assessment has been updated and remains unchanged, valid until June 18, with an additional update planned for the same date.

Update 20. May

Ongoing uplift is recorded in Svartsengi, a sign of continued magma accumulation. If this rate holds, the potential for a magmatic dike or eruption may begin to rise as autumn approaches. Yet, fluctuations in uplift—and thus magma accumulation—could certainly impact this assessment.

Scientists at the Icelandic Meteorological Office continue to explore potential future scenarios stemming from the ongoing magma gathering in Svartsengi.

Earthquake activity around the dike formed on April 1 remains reduced. Most seismic events are concentrated towards the southern end of the dike, and both the seismological activity of Fagradalsfjall and the surrounding areas have seen a decline.

The hazard map has undergone revisions and is effective until June 3, unless conditions evolve. The next update is also scheduled for June 3.

Update 6. May

• Uplift at Svartsengi persists, albeit at a gradually decreasing rate.

• Based on recent magma accumulation data, the likelihood of a new eruption rises as autumn approaches.

• Seismic activity linked to the dike is in decline.

• The hazard assessment map has been updated and will remain valid until May 20, unless conditions change.

Deformation data clearly indicate ongoing uplift at Svartsengi, although the pace has slowed in recent weeks. Scientists are currently evaluating when the possibility for a new magma intrusion or eruption might increase. This assessment posits that the volume of magma beneath Svartsengi would need to match those observed historically during similar events in the Sundhnúkur crater row. Should uplift continue at its current rate, the chance for a new dike or eruption is expected to rise with the coming autumn. However, rates of uplift—along with magma accumulation—could influence this evaluation.

Experts at the Icelandic Meteorological Office are now reevaluating potential scenarios, including determining the necessary magma volume beneath Svartsengi to initiate a dike or even a full eruption.

Changes in Uplift Rate Assessed Over Weeks, Not Days

Deformation data indicating uplift can often fluctuate day-to-day, even if magma inflow remains consistent. These minor variations can be attributed to weather conditions, measurement inaccuracies, or other natural phenomena that have negligible implications for the overall assessment. Focusing on shorter time frames might misrepresent uplift trends, making week-long or longer analyses essential. Therefore, it’s vital to interpret these data in the context of extended trends rather than isolated daily measurements.

Seismic activity continues along the dike formed on April 1, though it has diminished since late April. Daily earthquake counts typically average in the dozens across the past fortnight.

The hazard assessment map has been updated and is effective until May 20, unless subsequent changes occur. An information update is also planned for that same date.

Update 22 April, 12:30 UTC

• Significant micro-earthquake activity persists around the dike intrusion.

• The hazard assessment has been revised and will be valid until May 6, assuming no further changes.

Ongoing uplift at Svartsengi continues, though the rate has significantly declined, aligning more with pre-eruption figures recorded prior to the April 1 event. Continued magma accumulation beneath Svartsengi necessitates consideration of potential new magma intrusions or eruptions from the Sundhnúkur crater row.

The Icelandic Meteorological Office remains vigilant, monitoring magma accumulation trends while assessing potential future scenarios based on the latest data.

The accompanying map displays seismic activity on the Reykjanes Peninsula over the past week. The majority of quakes occurred near the April 1 magma intrusion and within the western part of Fagradalsfjall. The varied colors signify the timing of these seismic events, with red marking recent occurrences and blue representing activity from a week prior.

Micro-earthquake activity persists near the magma intrusion formed on April 1, with an average of about one hundred quakes per day recorded last week. Most of these tremors register below magnitude 1, although a notable earthquake of magnitude 1.7 was detected. Minor seismic activity also occurred near Fagradalsfjall last weekend. Calm weather has facilitated the monitoring network’s ability to capture even the smallest tremors, which might otherwise evade detection due to background noise from weather conditions.

The hazard map has been updated and remains valid until May 6, assuming no significant changes occur.

News Update 15 April

• The deformation rate at Svartsengi has diminished.
• Seismic activity regarding the dike intrusion is waning.
• A revised hazard assessment map is now in effect as of April 15.

Although minor seismic activity continues around the dike formed on April 1—recording dozens of earthquakes daily—the largest quake over the past week was a 3.3 magnitude event on April 13, located near the northern part of the dike intrusion, approximately 4 km ENE of Keilir. Most quakes remain under magnitude 2 and occur at depths ranging between 2 to 6 km.

Although uplift at Svartsengi continues, the pace has reduced compared to the previous week. Presently, the uplift rate is approximately twice as rapid as that observed just before the last eruption, aligning more closely with past patterns at the beginning of the current eruption cycle initiated in 2024.

The Icelandic Meteorological Office continues to monitor the region for magma accumulation patterns, assessing potential future scenarios informed by the latest data. As long as magma continues to accumulate beneath Svartsengi, the possibility of subsequent magma intrusions and eruptions along the Sundhnúkur crater row remains a viable concern.

New Hazard Map Covering a Larger Area

A new hazard map has been published today by the Icelandic Meteorological Office to inform the public of the hazards resulting from the ongoing unrest in the Reykjanes Peninsula. This updated map supersedes a previous version, in use since November 2023, which detailed assessments across seven defined zones surrounding activity at the Sundhnúkur crater row.

The seven-zone map has undergone 108 updates since its inception on November 20, 2023. While effective, its limitations in assessing hazards beyond the clearly defined zones have been apparent.

Recent developments, including a magma intrusion reaching the northeastern segment of the Svartsengi volcanic system on April 1, 2025, alongside an eruption west of Fagradalsfjall in August 2024, underscore the need for a broader hazard assessment.

A new map has been developed to overcome the previous version’s limitations. This comprehensive approach not only caters to the Reykjanes Peninsula but also introduces a methodology applicable to other active volcanic systems throughout Iceland.

The layout and presentation of the new hazard map, replacing the previous seven-zone map as of April 15, 2025, incorporate several enhancements, such as a volcanic alert level system (see blue box 1), an expanded mapped hazard area (see blue box 2), and defined target zones (see blue box 3). For further details, please refer to the accompanying documentation.

The Hazard Map Is Based on Three Components

The new map introduces three significant updates:

1. Volcanic Alert Level – This indicates the present status of the volcanic system, utilizing a four-tier color-coded scale ranging from 0 (green) to 3 (red). This alert level is essential for determining the assessed hazard levels.

2. Mapped Hazards – This assessment results from a collective evaluation of seven potential hazards that may emerge: 1) seismic activity, 2) sinkholes, 3) fault movements, 4) eruptive fissures, 5) lava flows, 6) tephra fallout, and 7) gas pollution. The mapped hazards indicate cumulative risk levels relative to the volcano’s status, with the shapes and extents of hazard zones likely to fluctuate according to ongoing evaluations.

3. Target Zones – Following an assessment of various hazards, the average hazard level is computed within pre-defined target areas, detailing contributing hazards for each zone. The dimension and structure of these target zones remain constant, even as their associated hazard levels may evolve over time.

More detailed insights into the hazard assessment process, the methodology underlying the volcanic alert level system, and the data employed in these evaluations can be found at the Icelandic Meteorological Office’s official site.