The magma chamber is not as deep as previously thought

The eruption at Sundhnúkagígar crater row is still active.

The eruption at Sundhnúkagígar crater row is still active. Photo/Hörður Kristleifsson

The findings of the Uppsala University of Sweden's seismic group contradict the previous notion of the location of the magma chamber under Mt Fagradalsfjall.

It was previously thought to be located at the top of the mantle at a depth of more than 15 km but according to the results of the seismologists, it is located directly under Mt Fagradalsfjall at a depth of 8 to 12 km, i.e. in the upper part of the lower crust.

The magma chamber in question is about 10 km wide and contains rather primitive magma.

This is revealed in an announcement of the University of Iceland’s Volcanology and Natural Hazard Unit.

The drawing shows the relative location of the magma chambers …

The drawing shows the relative location of the magma chambers and the magma channels that move the magma to the eruption site. Explanation drawing/UI’s Volcanology and Natural Hazard Unit.

Came straight from the deeper magma chamber

The shallow magma reservoir, located about 4 to 5 km below Svartsengi, holds more advanced magma.

The magma flows from the deeper magma reservoir to the upper reservoir, which is the cause of the inflation in Svartsengi.

The scenario has been such that when the shallow reservoir is full, and has taken in about 10 to 15 million cubic meters of magma, the roof breaks and a volcanic eruption breaks out.

Stalled at the shallow reservoir

The magma that flowed in the eruptions in the Mt Fagradalsfjall system from 2021 to 2023 came directly from the deeper magma reservoir.

The magma in the eruption at the Sundhnúkagígar crater row was detected from the same chamber, i.e. the deeper magma reservoir, but with a stop in the shallower reservoir.

The magma appeared to have been in the shallow reservoir for about 3 to 5 weeks where it developed, becoming lighter before it came to the surface in the eruption.

However, a change has occurred in this axis of events in the current eruption.


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