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 brought noticeable air pollution to the region. Volcanic haze has settled across much of the area — not all of it picked up by the national air quality monitoring network. The Icelandic Meteorological Office warns that gas emissions are expected to linger over South and West Iceland, with light winds doing little to clear the haze from the southwest. People who are sensitive to air quality should stay indoors as much as possible, and guidance on reducing exposure inside the home is available.

As of 15 July 2025, data show a slight slowdown in the uplift rate at Svartsengi, though the trend has not reversed. Roughly two-thirds of the magma that drained from the chamber during the seismic activity on 1 April has since been replenished. If accumulation continues at this pace, the probability of a magma intrusion or eruption may increase as autumn approaches.

Seismic activity has ticked up slightly around both the Sundhnúkur area and Fagradalsfjall over the past few weeks.

The hazard assessment for Svartsengi is unchanged and remains valid until 29 July 2025, when a scheduled update will be published. Any major shift in conditions would prompt an earlier revision.

The accompanying hazard map outlines the current dangers in the Svartsengi area, covering both the threats that exist right now and those that could develop if volcanic activity continues.

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 confirm that uplift at Svartsengi is continuing, though the rate has eased off in recent weeks. Scientists at the Icelandic Meteorological Office say that if magma keeps accumulating, the chance of an intrusion or eruption will grow over the autumn months. A volume of magma comparable to what preceded previous events is thought to be necessary before an eruption becomes likely.

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

This image shows estimated changes in magma volume within the crust at Svartsengi. Each colour represents a distinct period of magma activity. Week to week the accumulation looks fairly steady, but the inflow rate has been gradually declining over time.

Image 2: GPS Measurements from Svartsengi (SENG)

The data shows deformation in the north (top image), east (middle image), and vertical (bottom image) directions from November 2023 to June 17, 2025. Uplift is ongoing as seen in the bottom image, but its pace has slowed in recent weeks. Red lines mark significant events such as magma intrusions and eruptions. The current uplift rate has reduced recently.

Image 3: GPS Measurements from Fagridalur (FAGD)

This data captures movement and deformation at GPS station FAGD, located west of Fagradalsfjall, showing northward, eastward, and vertical movement. The station was established during the summer of 2024, so the record does not extend further back. Blue lines mark intrusions without associated eruptions; red lines indicate eruptions. The intrusion on April 1 occurred just west of this station, triggering clear southeastward shifts as the magma pushed through.

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

When a magma intrusion occurs, a graben forms above the intrusion site, with the crust on either side moving outward and upward. At the same time, subsidence is recorded at Svartsengi as magma leaves the chamber and flows into the dike.

Measurements near Svartsengi reflect both of these effects — there is visible subsidence at the SENG GPS station, though less pronounced than the signal from the dike formation itself. When modelling magma accumulation beneath Svartsengi, the deformation caused by dike formation has to be factored out. As a result, uplift around Svartsengi has returned to pre-April 1 levels, even though only slightly more than half of the magma volume that left the chamber has been replenished so far (refer to Image 1).

Earthquake Activity

Seismic activity remains steady at roughly ten micro-earthquakes per day. Most of the activity is centred just north of Grindavík.

Hazard Map

The hazard map has been revised and will remain in effect until 15 July 2025. It is largely similar to the previous version, but a few changes are worth noting.

Image 4: IMO’s Hazard Map

The area between Vogaheiði and Fagradals-Hagafell has been reclassified from moderate to low hazard. This follows a reassessment of the eruptive fissure risk, which is now considered lower than before. Similar changes apply to the southwestern end of Zone A (Grindavík). For further details on the reassessment process, please refer to this link.

Sinkhole hazards are now recognised as a potential threat in Zone C (Vogar). This follows an earlier oversight regarding fractures that appeared during the last eruption on 1 April. The magmatic dike reached further northeast than had been noted, but minor fractures in the southeastern corner of this area went unreported until a careful review brought them to light.

The hazard map is designed to convey immediate risks as well as potential threats tied to the continuing 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 eased compared to earlier periods. As the situation develops, the chance of a magma intrusion or eruption is expected to rise heading into autumn.

Between ten and twenty small earthquakes per day have been occurring around the dike from the April 1 eruption, though that rate has been steadily declining. Most earthquakes cluster in two areas: one near the southern end of the dike close to Grindavík, and another between Sundhnúkur and Stóra Skógfell. Occasional tremors can still be picked up near the northern end of the dike, north of Keilir.

The hazard assessment has been updated and remains unchanged, valid until June 18, with a further update planned for that date.

Update 20. May

Uplift continues to be recorded at Svartsengi, reflecting ongoing magma accumulation. If the current rate holds, the potential for a magmatic dike or eruption could begin to grow as autumn nears. That said, changes in the uplift rate — and by extension in magma accumulation — could certainly alter this picture.

Scientists at the Icelandic Meteorological Office are continuing to work through possible future scenarios based on the magma gathering beneath Svartsengi.

Earthquake activity around the dike formed on April 1 has remained subdued. Most events are concentrated toward the southern end of the dike, and seismicity around Fagradalsfjall and its surroundings has also declined.

The hazard map has been revised and is in effect until June 3, unless conditions change. 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 show ongoing uplift at Svartsengi, though the pace has slowed in recent weeks. Scientists are working to determine when the window for a new magma intrusion or eruption might open. The working assumption is that the volume of magma beneath Svartsengi would need to reach levels seen historically during comparable events along the Sundhnúkur crater row. If uplift continues at its current rate, the chance of a new dike or eruption is expected to increase come autumn — though changes in uplift and accumulation rates could shift that timing.

Experts at the Icelandic Meteorological Office are reassessing possible scenarios, including pinning down how much magma needs to collect beneath Svartsengi before a dike or full eruption becomes likely.

Changes in Uplift Rate Assessed Over Weeks, Not Days

Day-to-day deformation readings can bounce around even when the underlying magma inflow is steady. Weather conditions, measurement noise, and other natural factors can all introduce short-term variation that has little bearing on the bigger picture. Looking at only a day or two can give a misleading impression of whether uplift is accelerating or slowing — weekly or longer trends are what actually count. It is always worth keeping individual data points in that wider context.

Seismic activity continues along the dike formed on April 1, though it has quietened since late April. Daily earthquake counts have typically averaged in the dozens over 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.

Uplift at Svartsengi is ongoing, though the rate has dropped considerably and is now closer to what was recorded just before the April 1 eruption. With magma continuing to build up beneath Svartsengi, the possibility of fresh intrusions or eruptions along the Sundhnúkur crater row cannot be set aside.

The Icelandic Meteorological Office is keeping a close watch on magma accumulation trends and is working through potential future scenarios based on the most recent 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 continues near the magma intrusion formed on April 1, averaging about one hundred quakes per day last week. Most register below magnitude 1, though one notable event reached magnitude 1.7. Some minor seismic activity also occurred near Fagradalsfjall last weekend. The calm weather has helped the monitoring network pick up even the smallest tremors — events that would normally be masked by background noise during windier 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.

Minor seismic activity continues around the dike formed on April 1, with dozens of earthquakes recorded each day. The largest over the past week was a 3.3 magnitude event on April 13, 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.

Uplift at Svartsengi is continuing, though the rate has eased compared to the previous week. It is currently running at roughly twice the speed recorded just before the last eruption — closer to patterns seen at the start of the current eruption cycle that began in 2024.

The Icelandic Meteorological Office is monitoring magma accumulation and evaluating potential future scenarios using the latest available data. As long as magma keeps building beneath Svartsengi, the prospect of further intrusions and eruptions along the Sundhnúkur crater row remains real.

New Hazard Map Covering a Larger Area

A new hazard map has been published today by the Icelandic Meteorological Office to keep the public informed about risks from the continuing unrest on the Reykjanes Peninsula. It replaces an earlier version that had been in use since November 2023 and covered seven defined zones around the Sundhnúkur crater row.

That seven-zone map received 108 updates between its launch on November 20, 2023 and now. It served its purpose well, but assessing hazards beyond the boundaries of those defined zones was always a limitation.

Two developments in particular highlighted the need for a broader approach: a magma intrusion that pushed into the northeastern part of the Svartsengi volcanic system on April 1, 2025, and an eruption west of Fagradalsfjall in August 2024.

The new map was designed to address those gaps. It covers the full Reykjanes Peninsula and introduces a methodology that can also be applied to other active volcanic systems across 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, using a four-tier colour-coded scale running from 0 (green) to 3 (red). The alert level feeds directly into the assessed hazard levels shown on the map.

2. Mapped Hazards – This reflects a combined evaluation of seven potential hazards: 1) seismic activity, 2) sinkholes, 3) fault movements, 4) eruptive fissures, 5) lava flows, 6) tephra fallout, and 7) gas pollution. The mapped hazards show cumulative risk relative to the volcano’s current status, and the shapes and extents of hazard zones may shift as assessments are updated.

3. Target Zones – Once individual hazards have been assessed, the average hazard level is calculated within pre-defined target areas, with contributing hazards listed for each zone. The size and layout of these target zones stay fixed, even as their associated hazard levels may change over time.

More detail on the hazard assessment process, the methodology behind the volcanic alert level system, and the data used in these evaluations is available on the Icelandic Meteorological Office’s official site.