Fagradalsfjall eruptions challenge our knowledge of volcanoes
Fagradalsfjall eruption revealed new information modifying the knowledge acquired on how volcanoes work. It is a tuya-like volcano, formed during the last ice age on the Reykjanes Peninsula, about 40 km from Reykjavik, Iceland.
Matthew Jackson, an earth scientist from the University of California at Santa Barbara, and his colleagues took samples of magma from this volcano. Surprisingly, their analysis showed a rather active process. The study was published in the journal Nature.
They were able to take lava samples
The 60,000 earthquakes occurred on the peninsula for weeks kept most of the Icelandic population in suspense. Lava then erupted, spilling out of the hole in the ground of the relatively empty region of Geldingadalur. The eruption that occurred is not entirely due to the awakening of Mount Fagradalsfjall. It is rather a small fissure eruption in the southwestern lowlands of Iceland.
This event attracted many scientists and visitors who wanted to see the formation of the new section of the earth’s crust. Right from the start, scientists were able to get a little closer to collect lava samples continuously. This could have been done thanks to the slow flow of the lava as well as the impetuous blowing of the winds, sweeping away the harmful gases.
Led by Sæmundur Halldórsson of the University of Iceland, geologists wanted to know how deep this lava originated, where it was stored before the eruption, and what was happening in the reservoir before and during the eruption.
Abnormal, abrupt and extreme changes
According to the commonly held model, a magma chamber fills slowly over time, and the magma mixes. It then drains during the eruption. It is therefore unlikely that significant changes will occur in its chemical composition as it drains from the earth. However, the team found very high change rates in Iceland for key chemical indicators.
This fluctuation would be the result of successive batches of magma flowing into the chamber from the depths of the mantle. During the first weeks, the magma which had accumulated in the tank was of the type “impoverished”. In April, analyzes showed that the magma present in the chamber was of the “enriched” and of different composition. In May, the magma dominating the flow was deep and enriched type. These rapid and extreme changes could never be observed in near real time.
Nevertheless, Jackson said that this phenomenon may not be uncommon. Researchers have not yet been able to sample eruptions at such an early stage. Also, it is not yet known to what extent this phenomenon is representative of other volcanoes or what role it plays in triggering an eruption.