Iceland volcano eruption opens a rare window into the Earth beneath our feet

The recent Fagradalsfjall eruption in the southwest of Iceland enthralled the whole world, including nature lovers and scientists alike. The eruption was especially important as it provided geologists with an unusual opportunity to study the compositional evolution of magmas in near real-time.
Iceland volcano eruption opens a rare window into the Earth beneath our feet

The 2021 Fagradalsfjall eruption on Iceland was a landmark event - firstly because it was the first eruption in a populated area in Iceland for nearly 800 years and secondly because it provided geologists with a rare opportunity to study magmas that were accumulated in a deep crustal magma reservoir but ultimately derived from the Earth’s mantle (below 20 km). 

A research team from USA (University of Oregon), Sweden (Uppsala University), Iceland (University of Iceland), and Germany (GFZ) took this exceptional opportunity to collect lava samples every few days in order to construct a time-integrated catalogue of samples with which they could monitor the geochemical evolution of magma throughout the eruption to a degree of detail rarely achieved before. Usually, when volcano scientists look at past eruptions they work with a limited view of the erupted materials – for example older lava flows can get wholly or partially buried by newer ones. However, at Fagradalsfjall, the eruption was so well monitored and sampled that scientists had a chance to capture the compositional evolution of an Icelandic eruption in near real-time.

A member of the research team sampling red-hot lava at the active lava flow front at Fagradalsfjall. Photo by Anna María Guðmundsdóttir

The team were very interested in oxygen isotopes. Why? Because oxygen makes up about 50% of all volcanic rocks and its isotope ratios are sensitive tracers of mantle and crustal materials. In this way, oxygen isotopes can help scientists to determine if magma is reflective of its mantle source or if it interacted with crustal materials as it made its way to the surface. However, in addition to oxygen, the other vast suite of elements making up the volcanic rocks threw up some surprises. For instance, the team observed that the products of this single eruption contained roughly half of the trace element entire diversity of mantle-derived magmas previously recorded for the whole of Iceland.

The volcanic eruption at Fagradalsfjall, Iceland in 2021. The research team analyzed lava samples to determine the chemical and oxygen isotope composition of the magma supplying the eruption from depth. Photo by Alina Shevchenko and Edgar Zorn (GFZ Germany).

In brief, geochemical results show that the latest Icelandic eruption was supplied by magmas derived from multiple sources in the Earth’s mantle, each with its own distinctive elemental characteristics. To the amazement of scientists, each of these domains had identical oxygen isotope ratios. This result was remarkable and has never been observed before at an active eruption. The study provides new and compelling evidence for distinct mantle-sourced magmas having uniform oxygen isotope ratios, which can help us to better understand mantle dynamics and refine mantle models for Iceland.

A model cartoon summarizing the study's findings. Source: Bindeman et al. (2022).

Article information:

Bindeman, I.N., Deegan, F.M., Troll, V.R., Thordarson, T., Höskuldsson, A., Moreland, W.M., Zorn, E.U., Shevchenko, A.V., Walter, T.R. (2022) Diverse mantle components with invariant oxygen isotopes in the 2021 Fagradalsfjall eruption, Iceland. Nature Communications 13, 3737.


Utbrottet i Fagradalsfjäll öppnade sällsynt fönster för vulkanforskare

Vulkanutbrottet i området Fagradalsfjäll på sydvästra Island har hänfört såväl naturälskare som forskare. Utbrottet gav geologer ett unikt tillfälle att studera magma som samlats i en magmareservoar djupt i jordskorpan och härstammar från jordens mantel (minst 20 km under jordytan).

Ett forskningsteam från University of Oregon, Uppsala universitet, University of Iceland och Deutsches GeoForschungsZentrum (GFZ) tog förra året tillfället i akt att samla lavaprover flera gånger i veckan för att skapa ett tidsbaserat register av prover, och för att följa utbrottets geokemiska utveckling i sällan skådad detalj. När vulkanforskare undersöker äldre utbrott arbetar de oftast med en begränsad bild av det erupterade materialet – till exempel kan äldre lavaflöden bli helt eller delvis begravda av nya. Vid Fagradalsfjäll var utbrottet väl övervakat och prover togs så pass frekvent att forskarna kunde dokumentera utbrottets evolution nästan i realtid.

Forskarna var intresserade av syreisotoper. Varför då? För att vulkaniska bergarter till ungefär 50 procent består av syre och med hjälp av kvoterna mellan syreisotoper kan man spåra ursprunget hos material från manteln och jordskorpan. Med syreisotoperna kan forskare därför fastställa om magman härrör från manteln eller om den har interagerat med jordskorpan på vägen upp mot ytan. När det kommer till de många resterande ämnen som de vulkaniska bergarterna består av, utöver syre, visade resultaten på flera överraskningar. Till exempel observerade forskarna att innehållet från detta utbrott täckte in ungefär hälften av den mångfald av mantelmagmor som man tidigare dokumenterat för hela Island.

I korthet visar de geokemiska resultaten att magman från det senaste utbrottet på Island härrör från flera olika platser i jordens mantel med sina egna distinkta grundämnesegenskaper. Till forskarnas häpnad hade alla områden identiska syreisotopkvoter. Resultatet är anmärkningsvärt och har aldrig tidigare observerats vid ett aktivt utbrott. Den nya studien ger nya och övertygande bevis för att distinkt skilda magmor från manteln har enhetliga syreisotopkvoter, vilket kan hjälpa oss att bättre förstå manteldynamik och förfina Islands mantelmodeller.

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Go to the profile of Yan Zhang
over 1 year ago

nice work!

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