Uplift Activity Persists at Svartsengi Geothermal Site

Dike Intrusion on April 1: The Largest Since November 2023

April 8, 2025

Updated April 8, at 16:15 UTC

• Microseismic activity persists near the dike but is gradually decreasing.
• Evidence of ongoing uplift beneath Svartsengi remains strong.
• The current uplift rate exceeds that experienced after previous eruptions.
• It is premature to determine the future rates of magma accumulation.
• Approximately 30 million cubic meters of magma escaped the chamber on April 1, marking the largest intrusion since November 10, 2023.
• The hazard assessment has been updated and is in effect until April 15, given stable conditions.
• With magma continuing to gather beneath Svartsengi, the likelihood of further intrusions or eruptions remains high.

Current data indicates significant ongoing uplift beneath Svartsengi, with a rate of increase that outpaces previous eruptions. This trend can likely be attributed to the substantial volume of magma — around 30 million cubic meters — discharged during the recent event.

Nevertheless, it is too early to forecast how magma accumulation rates will progress. Historical patterns suggest a decline in these rates as the time between eruptions lengthens. It will likely take at least a week to discern any shifts in accumulation rates.

All indications suggest a steady inflow of magma into the Svartsengi system, signaling that volcanic activity in the Sundhnúkur crater row is far from over. The Icelandic Meteorological Office is closely monitoring developments and evaluating potential scenarios based on the latest information.

The data illustrates displacement at GPS station SENG in Svartsengi from November 11, 2023, including movements in the north, east, and vertical directions (top, middle, bottom). The latest measurement (April 7) is indicated by a green dot. Red lines denote the last eight eruptions (December 18, 2023; January 14; February 8; March 16; May 29; August 22; November 20, 2024; and April 1, 2025). Blue lines mark prior magma intrusions that did not result in eruptions (November 10, 2023, and March 2, 2024).

Dike Intrusion: The Largest Since November 2023

Modeling estimates suggest that approximately 30 million cubic meters of magma flowed from the chamber beneath Svartsengi into a newly created dike on April 1. This represents the most significant magma intrusion recorded since November 10, 2023.

Microseismic activity continues to be detected along the northern segment of the dike. Additionally, triggered earthquakes are observed near Reykjanestá and west of Kleifarvatn. While deformation in the northern part of the dike has decreased, movement is still evident in the vicinity of the dike itself, according to GPS stations and satellite imagery.

Updated Hazard Assessment

The hazard assessment has been revised and is valid until April 15, barring any major changes.

Significant updates have occurred across various zones since the previous assessment:

• Zone 3 (Sundhnúkur crater row) has been downgraded from “high” (red) to “considerable” (orange).
• Zones 4 (Grindavík), along with Zones 5, 6, and 7, have shifted from “considerable” (orange) to “moderate” (yellow).
• Zone 1 remains classified as “moderate” (yellow).

Despite these adjustments, there remains a notable risk of ground subsidence into established faults.

Updated April 4, at 14:55 UTC

• There are signs that uplift has resumed in Svartsengi.
• Seismic activity near the dike has shown a decrease.
• Deformations continue to be detected at GPS stations around the northern dike.
• Uncertainty persists regarding developments in the coming days, and magma movements within the dike remain a possibility.
• Triggered quakes at Trölladyngja last night, including one measuring 3.9 in magnitude, were recorded.
• The hazard assessment has been updated and remains valid until April 8 unless conditions shift.

Recent GPS measurements suggest that uplift may have resumed in Svartsengi, likely due to continued magma accumulation below the surface. However, some part of the uplift can also be attributed to the dike formation on April 1. Deformation data continues to confirm movement at GPS stations in areas like Vogar and near Keilir. Satellite images have also captured displacement between April 2 and 3.

Decreasing Seismicity, Yet Deformation and Microseismic Activity Persist

The seismic activity over the northern part of the dike is gradually diminishing, though small earthquakes persist in the region. Recent monitoring has recorded about 20 to 30 earthquakes per hour, mostly below a magnitude of 1.0, while peak rates had exceeded 100 earthquakes per hour. The distribution of these earthquakes extends from Stóra-Skógfell in the south to just north of Keilir, primarily at depths between 4 to 6 km.

The majority of magma that escaped Svartsengi has settled in the dike formed on April 1, reaching depths of approximately 1.5 km in certain areas. Although the deformation and microseismic activity remain notably high, there is a decreasing trend. Nevertheless, uncertainty lingers about future developments, and potential magma movements within the dike must still be considered.

The attached map illustrates all reviewed earthquakes on the Reykjanes Peninsula over the past 24 hours. It also highlights preliminary estimates of the dike’s location, extending from Grindavík to an area roughly three kilometers northwest of Keilir. The blue bars depict the hourly number of earthquakes—both reviewed and unreviewed—since the morning of April 1, showing a decline in total seismic events over the past day. The earthquake magnitudes have continued to diminish, with darker circles indicating reviewed events.

Swarm Near Trölladyngja Likely Triggered by Stress Changes

A significant earthquake swarm began near Trölladyngja at 5:30 PM on April 3, with the largest quake measuring 3.9 in magnitude recorded around 11 PM. Reports indicate these tremors were felt in surrounding populated areas, but activity began to decline after midnight. It appears that these earthquakes were triggered by stress changes following the dike intrusion on April 1, and the likelihood of similar events remains in nearby locations such as Trölladyngja and Reykjanestá in the coming days and weeks.

Hazard Assessment Unchanged

The Icelandic Meteorological Office has released an updated hazard assessment, maintaining the overall hazard levels across all zones. This assessment remains valid until 3:00 PM on April 8, unless revised further.

Experts from the Icelandic Institute of Natural History conducted an aerial survey of the eruption site on April 1, which confirmed that the lava field created during the six-hour eruption spanned approximately 0.23 km² and had an average thickness of about 1.7 m.

Updated April 3, at 15:25 UTC

• No eruptive activity has been noted at the fissure since yesterday afternoon, though faint glow persists in the new lava field.
• The newly formed dike stretches nearly 20 km, qualifying as the longest observed since seismic unrest kicked off in November 2023.
• Ground subsidence has exceeded 25 cm at the GPS station in Svartsengi since yesterday morning, continuing at a slower rate.
• More than 90% of the magma accumulated in the chamber beneath Svartsengi has shifted into the April 1 dike.
• The likelihood of a new eruptive opening along the dike is decreasing, although ongoing microseismicity prohibits complete dismissal of future activity.
• Displacements recorded across multiple GPS stations in connection with fault movements in Grindavík have been documented.

No activity has been observed at the eruptive fissure since yesterday afternoon, although residual glow remains evident in the newly formed lava. The area remains unstable and hazardous. Estimations indicate that the volume of lava from the recent eruption is around 0.4 million cubic meters, resulting in the smallest lava field observed since the eruption series began in December 2023. This volume represents roughly one-sixth of that from the January 2024 eruption, considered the second smallest during this period.

The accompanying map depicts the extent of the lava field formed during the last eruption, based on evaluations by the Icelandic Institute of Natural History.

Despite the modest size of the lava field, the extensive dike formed on April 1 illustrates that about 90% of the magma drawn from the chamber beneath Svartsengi has contributed to this feature, with only a small portion breaching the surface north of Grindavík.

Recent readings indicate a ground subsidence of over 25 cm at the GPS station in Svartsengi (SENG). Subsequent GPS data confirm ongoing subsidence, albeit at a reduced pace. This depletion reflects that the majority of magma has now migrated from Svartsengi into the newly established dike.

The provided graph illustrates four-hour solutions for the GPS station SENG, denoting displacements in the north, east, and vertical dimensions (top, middle, bottom).

Significant displacements related to faulting within Grindavík have also been recorded. The most substantial alterations were observed in the eastern segment of the town, with vertical movements exceeding 10 cm and horizontal shifts between 5-8 cm documented along Austurvegur. The western segment recorded around 6 cm of horizontal displacement. Since the inception of seismic activity yesterday, the cumulative displacements within Grindavík have reached approximately 50 cm across multiple faults.

Seismicity and Deformation Have Decreased Since Last Night

Since the onset of the magma intrusion around 6:30 AM on April 1, roughly 2,400 earthquakes have been detected in connection with dike formation. The dike progressed consistently northeastward until around 9 PM the prior night. Since that time, seismic activity has remained concentrated north of Fagradalsfjall, extending beyond Keilir. Although earthquake magnitudes have noticeably decreased compared to yesterday, the activity continues at a moderate level.

Deformation measurements reveal that the dike stretches beyond Keilir, correlating with the seismic distribution.

The outlined seismic data indicates activity over the dike from April 1, 6:30 AM to 12:00 PM. The visual breakdown includes earthquake magnitudes, hourly counts of seismic events, latitudes, and longitudes.

Likelihood of New Eruptive Opening Decreasing

Considering the current state of the southern dike segment, characterized by a lack of eruptive activity and diminished seismicity, the chances of a reinitiation of the recent eruption decrease over time. In the northeastern dike area, although the probability of new eruptive openings diminishes, sustained microseismicity prohibits outright dismissal of this possibility.

Future deformation measurements will illuminate whether magma continues to move from Svartsengi into the dike and how underground accumulation evolves. The latest hazard assessment will remain in effect until April 4 at 3:00 PM, unless significant changes arise. Key updates include:

• Zone 3 (Sundhnúkur crater row) has been revised down from very high (purple) to high (red).

• Zone 4 (Grindavík): Hazard status has shifted to considerable (orange) from high (red) owing to decreased likelihood of an eruptive opening.
• Zone 6’s classification has moved to considerable (orange) from high (red).

Geological assessments and monitoring of faults within Grindavík are outside the purview of the Icelandic Meteorological Office. GPS data hint at fault movement in Grindavík, closely tied to the dike intrusion of April 1.

The hazard map provided by the Icelandic Meteorological Office does not take into account personal risks associated with entering marked zones. Individuals are directed to rely on risk assessments prepared by the Government Task Force on Grindavík and the recommendations of the Suðurnes Police Commissioner.

Updated April 1 at 21:40 UTC

Webcam observations indicate no eruptive activity is visible at the fissure that opened earlier today just north of Grindavík. Only isolated glows remain detectable along the fissure and within the lava field.

Seismic activity and deformation related to magma movements persist at the northeastern end of the dike. Activity has been recorded across a roughly 20 km length, from the south end of the fissure to the site of the most intense seismicity.

These earthquakes are occurring at significant depths, with no signs suggesting that the moving magma is nearing the surface. Current modeling indicates that approximately 15 million cubic meters of magma have flowed from Svartsengi into the dike formed beneath the Sundhnúkur crater row, with a mere fraction reaching the surface. Before the eruption, about 22 million cubic meters of magma had accumulated in the reservoir underneath Svartsengi, indicating potential for further movements.

As seismic activity and deformation continue within the dike, the possibility of a new eruptive fissure must be considered, especially where seismic events are currently most concentrated. If eruptions were to occur, they may be accompanied by significant seismic activity, potentially perceptible to residents in Vogar.

The accompanying map illustrates reviewed earthquakes on the Reykjanes Peninsula since 6 AM on April 1.

Updated April 1 at 18:30 PM

Volcanic activity north of Grindavík is subsiding, with little visible activity detected in webcams or recent drone footage. Nonetheless, seismic activity persists. Near the southern section of the magma dike, activity has diminished, while the northern end remains vigorous, escalating towards the north in recent hours. The seismic events now extend nearly 9 km north of the northernmost eruption fissure formed during the August 2024 eruption, with the largest tremors recorded around magnitude 3, resonating in Vogar, situated about 7 km northwest of the active area.

The map presents the positions of earthquakes recorded on April 1, 2025, alongside known fault lines in the vicinity. The dominant fracture configuration is NE-SW, with no mapped fractures in the Vogar region.

Deformation assessments imply that magma flow from Svartsengi into the dike beneath the Sundhnúkur crater row persists, with seismic activity hinting at northeastern movement. Earthquakes are occurring at depths of around 4-6 km, and ongoing analysis of deformation data is underway. As long as significant seismic activity and deformation continue, the potential for magma to surface remains a possibility in the Sundhnúkur crater row or nearby areas of concentrated activity.

The following map illustrates the lava extent as of 12:34 PM, generated by the eruption that began earlier today. The map is based on ICEYE satellite imagery.

The hazard assessment has been revised and remains in effect until 3 PM on April 2, unless circumstances alter. The hazard level for Zone 3 (Sundhnúkur crater row) remains very high (purple). In Zone 4 (Grindavík), the hazard designation has dropped to high (red) due to lowered risks from ashfall and gas pollution. Changes have also been made to hazard levels in Zones 5 and 7, which have moved up from moderate (yellow) to considerable (orange) due to persisting seismic activity near the dike’s northeastern end.

Updated April 1 at 14:40 PM

Webcam observations reveal that volcanic activity has sharply diminished over the past hour.

Seismic activity continues, primarily localized at the northern and southern sections of the dike intrusion.

Deformation measurements consistently indicate ongoing northeastern movement, highlighting that magma is still flowing into the dyke.

Updated April 1 at 12:35 PM

The eruptive fissure has now extended to about 1,200 meters in length and continues to push southward.

The Icelandic Meteorological Office confirmed a broken hot water pipeline in northern Grindavík, further substantiating significant fault movements within the town.

Seismic activity is being continuously logged across the entire dike intrusion, with the most intense movements located at the northeastern end. The intrusion now extends over 3 km further northeast than observed in previous eruptions. Data also demonstrate ongoing displacement toward the northeast, reinforcing that magma is still traversing the dike.

Seismic data over the dike intrusion since 4 AM this morning, April 1.

Updated April 1 at 11:00 AM

The fissure continues to extend southward, with a new eruptive fissure developing a few hundred meters within the protective barriers north of Grindavík – nestled between the barriers and the town.

(The new fissure opening is on the left in the photo).

Weather forecasts predict southwesterly winds today, carrying volcanic gas northeastward, including toward the capital region. Winds are expected to calm this evening, condensing the gas pollution around the eruptive fissure. Tomorrow morning, winds will shift to northwesterly and eventually westerly, dispersing the gas southeastward and eventually eastward — potentially impacting Þorlákshöfn and Ölfus. The gas dispersion forecast is available here.

Seismic activity persists at the southern end of the magma intrusion and also north of Stóra-Skógfell. Earthquakes near Reykjanestá are likely triggered events resulting from stress releases associated with the seismicity in the Sundhnúkur crater row. Further updates can be found here.

Updated April 1 at 10:30 AM

Initial reports from the Coast Guard surveillance flight indicate the fissure has reached approximately 700 meters in length, maintaining a relatively stable status, although potential for further expansion either north or south persists. Ongoing seismic and deformation measurements continue to record activity.

The hazard assessment has been updated. The alert level for the Sundhnúkur crater row (Zone 3) is now classified as very high (purple), while the hazard level for Grindavík (Zone 4) has escalated from high (red) to very high (purple). This updated hazard assessment stands until April 2 at 10:30 AM unless conditions change.

Updated April 1 at 10:00 AM

The fissure has grown to approximately 500 meters and has breached the protective barrier north of Grindavík. The fissure’s expansion continues, and further growth southward is possible.

Updates from the Coast Guard helicopter are forthcoming.

The map depicts the fissure which has now reached about 500 m in length.

Updated April 1 at 9:45 AM

An eruption has been initiated just north of the protective barriers adjacent to Grindavík.

A Coast Guard helicopter will depart shortly to confirm the precise location and scale of the eruption.

The magma intrusion stretching under the Sundhnúkur crater row has now reached approximately 11 km, marking the longest recorded length since November 11, 2023.

Further details are forthcoming.

With the current wind direction, gas pollution resulting from the eruption will drift northeast, potentially affecting the capital area. Precise predictions for the intensity of this pollution remain uncertain.

Access the Icelandic Met Office’s gas dispersion forecast here.

Updated April 1 at 9:20 AM

Recent signals from GPS meters suggest stronger activity than seen in earlier events on the Sundhnúkur crater row, indicating a substantial magma movement.

The data demonstrates that magma is advancing both northeast and south towards Grindavík. At this point, it remains indeterminate where the magma will surface, yet it is pertinent to note that the southern displacement of deformation signals was not observed during the eruption in November 2024.

Emergency responders in Grindavík report that tremors are felt within the town, and visible signs of deformation suggest possible fault movements beneath its surface.

Updated April 1 at 7:25 AM

An earthquake swarm began around 6:30 AM this morning on the Sundhnúkur Crater Row, lying between Sýlingarfell and Stóra-Skógfell, reminiscent of patterns seen before previous eruptions.

This swarm was followed by a distinct shift in deformation and pressure changes in boreholes managed by HS Orka. Both data sources signify the onset of a magma intrusion.

No magma has yet surfaced, but an eruption appears increasingly probable.

Updates will continue.