O March 19, 2021 the Icelandic volcano Fagradalsfjall erupted and remained active until December of the same year, a phenomenon that attracted many tourists. now the magazine Nature publishes two studies, led by researchers from the University of Icelandregarding the seismic activity and the magma movements that occurred during the eruption and in the preceding weeks.
The volcano is located on the Reykjanes peninsula, about 40 kilometers from reykjavik. Over the past 3,000 years, its volcanic activity has been characterized by eruptive periods lasting 200 to 300 years, usually separated by epochs between 800 and 1,000 years. latency. The 2021 eruption began on the night of March 19, after about 800 years of inactivity
understand the precursor events of volcanic eruptions and Law Suit that occur during the eruptive activity, it is important to be able to issue alerts that prevent the loss of life s infrastructure damage.
Precursor events of the eruption
Taxes of ground displacement and the amount of earthquakes they tend to increase before volcanic eruptions, as magma rises to the surface.
Although the 2021 eruption was initially preceded by an increase in seismic activity and surface deformation −between February 24 and mid-March−, in the days prior to the onset of eruptive activity, an unusual decline both in soil deformation and seismicity.
The authors propose that forces are stored in the Earth’s crust – the most superficial layer – before eruptions due to the movements of the Earth’s surface. tectonic plates. These forces are released when magma enters the crust.
michelle parksfrom the Icelandic Meteorological Service and co-author of the study explains to SINC: “As the stored tectonic stress was released by the earthquakes, there was less lateral migration of magma, which resulted in a decrease in seismicity and deformation”.
“O magma it was forced to travel higher in the crust, which led to a reduction in motive pressure; Furthermore, the upper part of the crust here is weak, so the magma was able to move to the surface relatively silentno further increases in seismic activity prior to the start of the eruption,” he adds.
the later decrease in seismic activity and soil deformation could mean that this process is coming to an end and magma will erupt.
These findings demonstrate that the interaction between volcanic processes, tectonic stress, and crust composition must be taken into account when predicting eruptions, the researchers write.
“Our findings can help volcano monitoring institutions detect precursory signals before the onset of an eruption. The observed decrease in seismicity and deformation may be a precursor activity characteristic for a given class of eruptions, depending on the volcanic and tectonic environment,” concludes Parks.
Fagradalsfjall erupting, April 2021. / Iceland Meteorological Office
Changes in lava composition
At the second item the authors examined the lava ejected during the first 50 days of the eruption. The analyzes revealed a direct source of magmaa From the boundary between the earth’s crust and the mantle – the layer of rock beneath the crust. This interface zone is called the ‘Mohorovičić discontinuity’, or ‘Mold‘.
As described by the authors, the erupting lava changed over time; during the early phases of the eruptive activity, it came predominantly close to Moho, but during the following weeks its composition changed, indicating that it came from magmas generated in greater depths.
These findings demonstrate that the magma storage zone near Moho is an extremely dynamic. Furthermore, the gradual change in composition shows that newly formed magma can rapidly mix with existing magma over incredibly short timescales (days to weeks).
The authors note that Iceland is a unique geological scenery and these observations must be verified in the oceanic environment. However, these findings may contribute to the understanding of these types of volcanoes.