The eruption of Fagladar reveals the source of Fire in Iceland

2021 Fagladar eruption Image from Kristinn Ingvarsson, University of Iceland

Two teams of independent scientists reported on unexpected seismic and magmatic movements observed before and during the 2021 eruption of Iceland’s Fagladar volcano. The findings are important for understanding the processes that caused this eruption and for future monitoring of volcanic activity. The results of the study were recently published in Nature.

Fagladar Volcano is located on the Reykjanes Peninsula, about 40 km from Reykjavík, the capital of Iceland. Over the past 3,000 years, the volcanic activity of the Reykjanes Peninsula has been characterized by an eruption period of 200-300 years, with a dormancy period of 800-1000 years.

The 2021 eruption began on March 19 and was preceded by about 800 years of dormancy, with increased seismic activity and surface deformation in the weeks leading up to the eruption, but these activities were unusually weakened in the days leading up to the eruption. The eruption began with a low magma flow rate and little lava flow, but by the end of April an acceleration of magma flow could be observed, accompanied by a high lava fountain. Understanding the precursors of volcanic eruptions and the processes in them is important to warn of life-saving and infrastructure protection.

Freesteinn Sigmundsson of the University of Iceland, Michelle Parks of the Icelandic Meteorological Agency and colleagues studied the precursors of the eruption. Before many volcanic eruptions, the rate of ground displacement and the number of earthquakes increased as magma rushed to the surface. Although the 2021 Icelandic eruption saw an increase in seismic activity and surface deformation as early as February 24 to mid-March, deformation and seismic weakening were observed a few days before the eruption.

They believe that due to the movement of the surface plates, the pre-eruption force is stored in the earth’s crust. Before eruption, these forces are released as magma enters the earth’s crust, and subsequent seismic activity and surface deformation weaken or indicate that the process is temporarily over, and the magma is about to erupt. The results show that when predicting volcanic eruptions, it is necessary to consider the interaction between volcanic processes, tectonic stresses, and crustal structures.

In another study, Samundur Halldorsson and colleagues at the University of Iceland studied lava that erupted 50 days after the eruption. These analyses revealed that the magma came directly from the crust and mantle interface (near the Moho interface). They point out that the lava spewed out changes over time; At the beginning of the eruption, the lava came mainly from near the interface of this shell mantle, but in the following weeks, the lava composition changed, suggesting that it came from magma produced deeper.

The results suggest that the magma storage area near the Moho interface is a highly dynamic environment, with magma mixing on very short timescales (days to weeks). This indicates that the real-time formation of magma is very fast. The authors say the results are some of the first direct observations of basalt magma systems at this depth, and could improve our understanding of such volcanoes. (Source: China Science Daily Feng Weiwei)

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