Iceland’s Fagradalsfjall volcano erupts at night.
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Recent findings from Iceland’s Fagradalsfjall eruption have changed what we know about how volcanoes work.
Learning something that radically changes the way we understand our world doesn’t happen very often. But for Earth scientist Matthew Jackson of the University of California, Santa Barbara, and thousands of volcanologists around the world, this discovery has just happened.
While sampling magma from Iceland’s Fagradalsfjall volcano, Jackson and his colleagues discovered a much more dynamic process than scientists expected during the two centuries that scientists had studied the volcano.
“Just when I thought we were close to discovering how this volcano worked, we had a big surprise,” he said.
Fagradalsfjall is a Toya volcano that formed during the last ice age on the Reykjanes Peninsula, about 25 miles (40 km) from Reykjavik, Iceland.
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The geoscientists’ findings were published on September 14 in the journal temperament.
10,000 years per month
Thanks to his departure, the plague and 780 years of melting plutonic rocks, Jackson was in the right place and time to witness the birth of Fagradalsfjall, a fissure in the lowlands in southwestern Iceland that split open and exploded with magma in March 2021. At that time, everyone on the Rikjan peninsula is ready for some kind of volcanic eruption.
“The earthquakes have been very strong,” he said of the approximately 50,000 earthquakes – of magnitude 4 or greater – that shook the ground for weeks and shocked most Icelanders.
The sleep deprivation is worth it, however, and the weirdness quickly turns to magic when lava gushes and squirts from a hole in the ground in the relatively empty Geldingadalur. Scientists and visitors flock to the area to see the new piece of the earth’s crust. From the start, they were able to get close enough to take continuous lava samples, due to the slow lava flow and strong winds that blew the noxious gases away.
The volcanic eruption of Mount Fagradalsfjall in Iceland.
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Led by Simundur Halldorsson of the University of Iceland, the geologists sought to understand “the depth of origin of magma in the mantle, how much was deposited beneath the surface before an eruption, and what happened in the reservoir before and during an eruption. eruption. eruption. ” Questions like these, while basic, are, however, actually some of the biggest challenges for those who study volcanoes. This is due to unpredictable eruptions, extreme dangers and conditions, remoteness and inaccessibility of many active sites.
“The assumption is that the magma chamber slowly fills over time and the magma mixes well,” Jackson explained. “Then it dries up during the eruption.” As a result of this well-defined two-step process, he added, those who study volcanic eruptions do not expect to see significant changes in the chemical composition of magma as it escapes from the Earth.
“This is what we see on Mount Kolawea in Hawaii,” he said. “You will have volcanic eruptions that will last for years and there will be subtle changes over time.
“But in Iceland, there are more than 1,000 factors with a higher rate of change for key chemical indicators,” Jackson continued. “Within a month, the Fagradalsfjall eruption shows greater compositional variation than the Kīlauea eruption has shown in decades. The total range of chemical compositions sampled in this first lunar eruption covers the entire erupted range in southwestern Iceland. in the last 10,000 years “.
Night view of a volcanic eruption on Mount Fagradalsfjall in Iceland.
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This asymmetry is caused by the next batch of magma flowing into the chamber from the deepest mantle, according to the scientists.
“Imagine a lava lamp in your mind,” Jackson said. “You have a heating lamp at the bottom, the bubble heats up and the tip rises and cools and then sinks. We can think of the Earth’s mantle, from the top of the core to the bottom of the tectonic plates, which functions very much like a lava lamp. ” and the strong upward movement to the surface, the molten rock of these lumps accumulates in space and crystallizes, the gases escape through the crust and the pressure increases until the magma finds a way to escape.
“Just when I thought we were almost trying to understand how this volcano works, we got a big shock.” – Matthew Jackson
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As the paper shows, what erupts in the first few weeks is the type of “spent” magma that builds up.g in the reservoir, which is about 16 km below the surface. However, in April, evidence showed that the chamber was filled with a deeper “enriched” type that was reconstituted with a different composition. Obtained from a different region of the mantle plume that rises below Iceland. This new magma has a less modified chemical composition, with a higher magnesium content and a higher percentage of carbon dioxide. This indicates that less gas is escaping from this deep magma. In May, the magma that controls the flow is the deepest and richest type. This rapid and extreme change in the composition of the magma in this hot spot where they feed on feathers, they say, “has never been observed before in the foreseeable future.”
However, Jackson says these makeup changes may not be uncommon. However, the opportunity to sample eruptions at such an early stage is not uncommon. For example, before the 2021 Fagradalsfjall eruption, the most recent eruption occurred on Iceland’s Reykjanes Peninsula eight centuries ago. He suspects that this new activity signals the start of a new centuries-old volcanic cycle in southwestern Iceland.
“We often don’t have records of the early stages of most volcanic eruptions because they are buried by lava flows in the later stages,” he said. The project allows them, according to the researchers, to see phenomena believed to be possible but not directly visible.
For scientists, these findings represent a “major limitation” in the way we build models of volcanoes around the world. However, it is still unclear how representative this phenomenon is for other volcanoes, or what its role is in causing eruptions. For Jackson, it’s a reminder that the Earth still holds secrets.
“So when I go out to sample ancient lava flows, or when I read or write a future article, it will always be on my mind – this may not be the whole story of that eruption,” he said.
Reference: “Transformasi cepat Sumber magmatik Dalam by Gunung Berapi Vagradalsvilla, Iceland” oleh Somundur A. Halldorsson, Edward W. Marshall, Alberto Carracciolo, Simon Matthews, Eniko Bali, dan Maja B.. Guðfinnsson, Olgeir Sigmarsson, John Maclennan, Matthew G. Jackson, Martin J. Whitehouse, Heejin Jeon, Quinten HA van der Meer, Geoffrey K. Mibei, Maarit H. Kalliokoski, Maria M. Melissa Ann Pfeffer, Samuel W. Scott, Ricky Kiertensdottir, Barbara I. Klein, Clive Oppenheimer, Alessandro Ayuba, Evgenia Ilyinskaya, Marcelo Pettito, Gaetano Giudice dan Andrei Stefansson, 14 September 2022, temperament.
DOI: 10.1038 / s41586-022-04981-x
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