Sundhnúkur Crater Row Eruption Still Likely, Reports News

Magma Volume Beneath Svartsengi Reaches Record High

25 March 2025

Updated 25 March at 15:00 UTC

• Magma accumulation persists, though uplift rates have recently slowed.
• The most plausible outcome is a magma intrusion and/or eruption, likely originating between Sundhnúkur and Stóra-Skógfell.
• Seismic activity has been on the rise, suggesting increased pressure at the eruption site.
• An eruption could commence with little to no warning.
• The hazard assessment remains unchanged.

GPS data shows that magma is still building up beneath Svartsengi, though the rate of land uplift has eased off slightly in recent weeks. That slowdown hasn’t changed the overall picture — scientists still expect a magma intrusion and likely eruption along the Sundhnúkur crater row.

How large any eruption turns out to be will depend heavily on how much magma is released at the moment it breaks through. The volume currently sitting beneath Svartsengi is the highest recorded since this eruption series started in December 2023, which raises the real possibility that the next event could be bigger than anything seen so far. In six of the seven eruptions since volcanic activity resumed in late 2023, magma first reached the surface in the area between Sundhnúkur and Stóra-Skógfell. The January 2024 eruption was the exception, breaking through just south of Hagafell.

GPS displacement data from the SENG station in the Svartsengi area, recorded since November 11, 2023, illustrates movements in the north, east, and vertical directions. The most recent reading (March 24) is noted by a green dot, while the red vertical lines track the initiation of the last seven eruptions. Blue lines denote instances of magma intrusions that did not culminate in eruptions.

Seismic readings have been ticking upward gradually. The Sundhnúkur crater row has been the site of repeated magma intrusions and fissure openings, and that history has relieved crustal stress over time — meaning earthquakes in the lead-up to eruptions are less frequent and less intense than they were early in this sequence. Recent events have also confirmed just how short the warning window can be: the two most recent eruptions were preceded by only 30 to 40 minutes of heightened seismic activity.

The signals scientists watch for include notable earthquake swarms along the Sundhnúkur crater row, pressure changes in boreholes monitored by HS Orka at Svartsengi, deformation picked up in fiber-optic cables, and shifts in real-time GPS measurements.

The current hazard assessment runs until April 1, unless conditions change before then. More detail on what to expect if an eruption begins can be found at the provided link.

Updated 18 March at 13:00 UTC

• Magma accumulation continues, reaching the highest volume noted since December 2023.
• The likely conclusion of this magma accumulation phase is an intrusion and subsequent eruption.
• Seismic activity has seen a gradual increase, hinting at rising pressure at the eruption site.
• An eruption could commence with minimal warning.
• The hazard assessment maintains its current status and is valid until March 25.

Small bursts of seismic activity near the Sundhnúkur crater row have been happening most weeks — the last week of February was quiet, but that’s thought to be down to bad weather affecting detection rather than any real change in conditions. A seismic station that had been returning faulty readings has since been corrected. Earthquakes are still clustering in the same spots seen before earlier eruptions — between Sundhnúkur and Stóra-Skógfell, where magma has broken through before.

The accompanying image depicts earthquake activity around the Sundhnúkur crater row from the last eruption on December 8, 2024, to March 18. The map displays earthquake locations during this timeframe, with discrepancies needing correction for events east of the Sundhnúkur crater row. The lava field from the last eruption appears in gray, while dark red lines indicate previous eruption fissures.

Deformation Measurements Confirm Ongoing Uplift

GPS readings confirm the ground is still rising, even if the pace has slowed. There are no signs of subsidence anywhere in the Svartsengi area — neither GPS data nor InSAR observations suggest any deflation. The volume of magma accumulating beneath Svartsengi is still notably high by any measure since the eruption series began in December 2023.

This graph illustrates 8-hour solutions from the GPS station THOB at Þorbjörn, detailing movements in the north, east, and vertical directions.

The hazard assessment has been updated but is essentially unchanged in substance, and remains valid until March 25 unless something shifts before then.

Updated 17 March at 17:30 UTC

• The volume of magma beneath Svartsengi has not been this high since December 2023.
• The impending phase may culminate in a dike intrusion and an eruption.
• Recent seismic activity has indicated rising pressure.
• An eruption could commence unexpectedly.
• The current hazard assessment is effective until March 18.
• Seismic activities remain consistent with prior eruption lead-ups.

On March 11, the Icelandic Meteorological Office noticed something odd: earthquake locations were appearing several hundred meters east of where they’d been in the run-up to previous events. The initial theory was that this reflected genuine eastward migration due to mounting magma pressure, but scientists ran a high-resolution analysis to check. Seismic locations are pinpointed using signals from multiple seismometers, and an interference source was identified and corrected, allowing for more reliable readings going forward.

Earthquakes are still occurring in the zones near Sundhnúkur and Stóra-Skógfell that have been active before previous eruptions — the same spots where magma has made its way to the surface in the past.

The map captures seismic activity around the Sundhnúkur crater row over the last fortnight, with red circles indicating locations of earthquakes recorded in the preceding three days following the data adjustment. These events align with eruption fissures that have manifested since December 2023.

Updated 11 March at 16:20 UTC

• Magma accumulation continues at a steady pace.
• The magma volume beneath Svartsengi is at its highest since the eruption series began.
• Seismic activity has recently increased.
• A dike intrusion and eruption are plausible outcomes.
• Warning times for eruptions could be very short.
• The hazard assessment remains unchanged and is valid until March 18.

GPS measurements show land beneath Svartsengi is still rising, with magma accumulation continuing to build. The current volume has already surpassed what was recorded just before the eruption that started on November 20.

Seismic activity along the Sundhnúkur crater row is tracking closely with patterns seen before the November eruption.

Since that last eruption, the earthquake activity has shifted slightly eastward. This is likely tied to increased tectonic pressure caused by the ongoing magma buildup, though the shift alone doesn’t tell scientists where a future eruption would break through — that question is still being looked at carefully.

With magma continuing to accumulate, the probability of a dike intrusion and eruption stays elevated. If it happens, it would be the eighth eruption in this active period since late 2023.

The subsequent graph illustrates magma accumulation throughout the period of eruptions and dike intrusions since November 2023.

The Next Eruption May Exceed Previous Events

Three months have now passed since the last eruption — an 18-day event that ended on December 8 — making this the longest stretch of magma accumulation in the current eruptive series. Today marks 111 days since that eruption began on November 20, 2024.

The magma now sitting beneath Svartsengi is the largest volume recorded since the sequence started in December 2023. That means if an eruption does occur in the coming days or weeks, it could rival or exceed the August 2024 eruption, which was the largest yet by volume. As always, the actual size will depend on how much magma is released at the point of breakthrough — and that’s not something anyone can predict precisely in advance.

The graph presents the periods of magma accumulation leading to subsequent eruptions, alongside the lava field volumes resulting from those eruptions. Observations indicate that elapsed time between eruptions has been increasing since March 2024, with a corresponding rise in eruption size until August 2024. The lower magma volume in January 2024 resulted in smaller lava flows during that event.

The hazard assessment remains unchanged and will be valid until March 18, with further updates anticipated. For details on what to expect during the next eruption, please refer to corresponding resources.

Updated 4 March at 15:45 UTC

• Ground uplift continues at a steady pace.
• Inclement weather has inhibited seismic detection recently.
• An eruption may commence with very little warning.
• Expect a fissure to open between Sundhnúkur and Stóra-Skógafell.
• The impact radius of a volcanic eruption will depend on fissure orientation.
• The hazard assessment remains intact and is valid until March 11.

Deformation measurements confirm that the ground is still rising and magma is still accumulating beneath Svartsengi. Calculations put current magma levels above what was seen before the eruption that started on November 20.

This graph represents the development of magma accumulation and the estimated total volume beneath Svartsengi. The zero point relates to conditions before the uplift started in late October 2023.

Given the continued deformation and magma buildup, a dike intrusion and eruption remain a likely outcome in the coming days or weeks.

As with previous events, magma is expected to first reach the surface in the area between Sundhnúkur and Stóra-Skógfell — the pattern in six of the seven post-2023 eruptions. The January 2024 eruption was the only one to break that pattern.

What actually gets affected will depend on which direction any fissure grows — northward or southward.

Seismic activity has dipped slightly but that may simply reflect weather conditions reducing the sensitivity of instruments to smaller earthquakes. Stress relief from earlier eruptions also means the seismic footprint heading into a potential event will likely be lighter than it was in the early stages of this series.

Warning times have historically been very short — recent eruptions started within just 30–40 minutes of the first signs. The key indicators to watch are intensified earthquake swarms along the Sundhnúkur crater row, pressure changes in HS Orka’s boreholes, deformation in fiber-optic cables, and real-time GPS shifts.

Hazard Assessment Remains Unchanged

The current hazard assessment stays valid until March 11, barring any significant changes in conditions. The Icelandic Meteorological Office’s monitoring team is keeping close watch on developments.

Updated 25 February at 14:40 UTC

• While land uplift persists, it has exhibited slight slowing recently.
• Magma volumes beneath Svartsengi have exceeded pre-November 20 eruption levels.
• An eruption may initiate with minimal warning.
• The most likely site for an eruption is between Sundhnúkur and Stóra-Skógafell.
• The impacted area will hinge on fissure orientation.
• Seismic activity has gradually amplified.
• The hazard assessment is valid until March 4.

The ground is still rising, though the pace has eased compared to previous weeks. Modelling shows that magma accumulation has now exceeded the levels measured before the eruption that began on November 20, keeping the probability of an imminent event elevated.

Seismic activity has been picking up since January, and the hazard assessment has been renewed without changes, remaining in effect until March 4.

Updated 21 February at 14:15 UTC

• Updated models reveal magma beneath Svartsengi has reached levels recorded preceding the last eruption.
• An eruption may initiate with very short warning.
• Magma is likely to surface between Sundhnúkur and Stóra-Skógafell.
• Fissure orientation will determine eruption impact.
• Hazard assessment updated, raising hazard levels in three regions.

Updated modelling indicates that magma beneath Svartsengi has now reached roughly the same volume recorded before the November 20 eruption. Scientists consider an event in the coming days or weeks increasingly likely.

If an eruption does occur, it will be the eighth since late 2023. Reduced seismic activity and lower crustal stress mean fewer earthquakes before the event, which translates to shorter warning times — potentially as little as half an hour.

The signals that would indicate magma is on the move include small earthquake clusters, changes in borehole pressures, and shifts in real-time monitoring data.

Recent Earthquake Activity in the Sundhnúkur Crater Row

On the evening of last night at approximately 19:50, several earthquakes were recorded in quick succession between Sundhnúkur and Stóra-Skógfell, potentially signaling magma movement. Monitoring teams noted no other indications from instruments.

A similar pattern was seen on November 4, which turned out to be a precursor to the eruption that began on November 20.

Expected Impacts from Potential Eruptions

Magma is expected to rise between Sundhnúkur and Stóra-Skógafell, consistent with six of the seven prior eruptions. The January 2024 event was the outlier, emerging south of Hagafell. Exactly what gets affected will depend on which direction the fissures open.

• In the event of adverse wind directions, initial phases may present hazards, including gas pollution extending outwards up to a kilometer from the source.
• Lava may traverse Grindavíkurvegur Road towards Þorbjörn and/or Svartsengi in under 90 minutes.
• If lava encounters water bodies or groundwater, localized explosive activities could occur.

Data from the Icelandic Meteorological Office suggests that an eruption may also initiate south or north of Hagafell, with lava potentially reaching the Nesvegur and Suðurstrandarvegur roads within approximately 90 minutes. Such candidates could disrupt escape routes out of Grindavík within six hours.

Updated 18 February at 15:00 UTC

Increased Hazard Levels in Three Regions

Following updated model results, the Icelandic Meteorological Office has revised its hazard assessment, effective until February 25. Notable changes include heightened hazard levels in Area 1 (Svartsengi) and Area 5 from “moderate” (yellow) to “considerable” (orange), and an upgrade in Area 3, the Sundhnúkur crater row, from “considerable” (orange) to “high” (red).

Updated 14 February at 17:30 UTC

• Land uplift has continued, albeit at a reduced pace.
• Model assessments show closely approaching magma volume to that which has previously triggered dike intrusions and eruptions.
• Seismic activity in the Sundhnúkur crater row has remained relatively steady, averaging five recorded earthquakes per day.
• The hazard assessment remains unchanged and valid until February 25.

Deformation measurements confirm the ground is still rising, if a little more slowly. Recent modelling puts magma levels close to those that preceded earlier eruptions.

The accompanying image depicts model calculations of magma volume accumulating beneath Svartsengi over time, indicating a range that highlights thresholds for increased eruption likelihood.