Iceland Volcano: Continued Ground Uplift And Magma Accumulation In The Svartsengi Area

A volcanic eruption started at Sundhnúks crater row 22 August. This photo was taken one hour after the eruption started and the eruption fracture is estimated to be about 4 km long. Photo: Björn Oddsson/Civil Protection.

The volume of magma is now about two-thirds of what accumulated before the last eruption on August 22

ICELAND MET OFFICE

Updated 22. October at 15:30 UTC

• GPS measurements and model calculations in the Svartsengi area show that ground uplift and magma accumulation continue.
• If the current rate of magma accumulation in the reservoir continues, the lower uncertainty threshold for the volume of magma that might culminate in a dike intrusion or eruption will be reached in early November.
• The current hazard assessment remains in effect until October 29, barring any changes.

Ground uplift and magma accumulation beneath Svartsengi are progressing at a rate consistent with recent weeks. Seismic activity has slightly increased in recent days, with around five earthquakes per day occurring along the dyke. The largest earthquake had a magnitude of 1.5.

Model calculations based on GPS data indicate that the volume of magma that has accumulated beneath Svartsengi is now approximately two-thirds of what it was before the previous eruption, which began on August 22. 

If magma inflow continues at a similar rate, the lower uncertainty threshold that might feed a new intrusion or eruption is expected to be reached in early November. If a significant increase in seismic activity is detected around the same time, it could suggest that the likelihood of a new magma intrusion and a potential eruption is increasing. This likelihood will gradually rise as more magma accumulates and seismic activity intensifies.

A graph showing the progression of magma accumulation and the estimated total volume of magma in the reservoir beneath Svartsengi as of October 25 (red curve). The total volume of magma beneath Svartsengi is currently about two-thirds of what accumulated before the previous eruption began on August 22 (green curve).

Volume estimated through model calculations

The volume of magma that has accumulated beneath Svartsengi since the last eruption ended is estimated to be 14 million cubic meters, according to model calculations. It is estimated that around 24 million cubic meters of magma exited the magma chamber during the last eruption, which began on August 22 and was the largest eruption in this sequence of events. The uncertainty in these calculations is approximately +/- 5 million cubic meters. The volume of magma beneath Svartsengi is therefore projected to reach a value that is comparable to what it was before the last eruption when it enters within the range defined by the "lower uncertainty limit" (19 million cubic meters) and the "upper uncertainty limit" (29 million cubic meters).

The models, which are based on GPS data and are updated daily, indicate how much magma has accumulated since the last magma intrusion, providing an estimation of when the uncertainty thresholds may be reached. These models are based on the estimated inflow of magma into the reservoir beneath Svartsengi, and small changes in that flow can affect the final assessment. It is difficult to determine how far beyond these previously observed limits the magma volume can increase before an eruption starts. The trend has shown that the time between eruptions is increasing, as the volume of magma required to trigger the next magma intrusion or eruption appears to be increasing over time. It is possible that the risk of an eruption may be assessed to be high for some time before an event begins.

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