New research results suggest that the 2021 volcanic eruption on Iceland's Reykjavik Peninsula involved magma formed in the Earth's crust rather than coming directly from the Earth's mantle, overturning previous assumptions. Geochemical analyzes indicate that the source of the lava is the Earth's crust, and similar magma behavior has been observed in other recent volcanic eruptions around the world.
At first, it was thought that the recent lava on the Reykjavik Peninsula was erupted directly from the Earth's mantle, but geochemical evidence shows that the magma came from underground melting of the Earth's crust caused by the "Fagradersfjall Fire" that started in 2021. This was discovered by an international team of researchers from the Scripps Institution of Oceanography at the University of California, San Diego, the Department of Earth Sciences at Uppsala University, and the University of Iceland in Reykjavik.
By timing sampling of erupting magma, detailed time series analysis of geochemical signals can be performed. The analysis showed that the magma stayed in the crust for a period of time before erupting, in sharp contrast to the initial hypothesis that the magma rose directly from the mantle. The international research team published this research result in the journal Nature on July 31.
The research team has been studying basaltic lava from recent volcanic eruptions other than Iceland. These volcanoes include the 2021 eruption of Tahogait volcano on La Palma in the Canary Islands and the 2022 eruption of Hawaii's Mauna Loa volcano. They discovered similar magma pools beneath La Palma.
"Systematic lava sampling and subsequent analysis of changes in composition in the laboratory can help decipher the feeds deep within a volcano," said lead author James Day, professor of earth sciences at Scripps Institution of Oceanography. "It's a bit like measuring someone's blood on a regular basis. In this case, the volcano's 'blood' is the molten magma that gushes out of the volcano in spectacular fashion."
Specifically, previous research has shown that the Fagradlesfial fire erupted from the surface and had no interaction with the Earth's crust. The team used the isotopic composition of the element osmium to understand what's going on beneath the volcano. The earth is divided into a series of formations. The deepest part is the metal core. The shallowest layers are the atmosphere, oceans, and rocky crust.
Humans live on the Earth's crust, which is dominated by rock types such as granite or basalt, such as the lava in Iceland. Between the core and the crust is the huge mantle. The mantle is where melting creates magma, which feeds volcanoes in places like Iceland. Osmium is a very precious metal, like platinum or palladium. Osmium is special in that one of its isotopes is produced by the radioactive decay of another precious metal, rhenium. Because the two elements behave differently during the melting process, one element, rhenium, is enriched in the Earth's crust, while the other element, rhenium, is not.
The team was able to show that the 2021 lava was contaminated by the Earth's crust, while the 2022 lava was not. They concluded that the earliest lava must have pooled in the Earth's crust before erupting, while later eruptions took advantage of pre-existing pathways to the surface.
Valentin Troll, professor at the Department of Geosciences at Uppsala University, is a co-author of the study and the lead author of a study recently published in the journal TerraNova that investigated the magma conduit system in the Reykjavik volcanic region.
Volcanic eruptions on the Reykjavík Peninsula may still be ongoing, and while they would be devastating for residents of the evacuated town of Grindavik, these events will provide us with an important treasure trove of scientific information about how lava fields are formed and how magma migrates from the Earth's interior to the surface.
Compiled from /ScitechDaily