The Earth’s Newest Secret: Fundamental Changes to What We Know About How Volcanoes Work

Fagradalsfjall Volcanic Eruption at Night

Fagradalsfjall volcano in Iceland erupting at night.

Recent discoveries from Iceland’s Fagradalsfjall eruptions alter what we know about how volcanoes work.

Learning something that fundamentally changes how we understand our world doesn’t happen very often. But for University of California, Santa Barbara (UCSB) Earth scientist Matthew Jackson and the thousands of volcanologists across the globe, such a revelation has just occurred.

While sampling magma from the Fagradalsfjall volcano in Iceland, Jackson and his colleagues uncovered a process far more dynamic than anyone had assumed in the two centuries that scientists have been studying volcanoes.

“Just when I think we’ve gotten close to figuring out how these volcanoes work, we get a big surprise,” he said.

Fagradalsfjall is a tuya volcano formed in the Last Glacial Period on the Reykjanes Peninsula, around 25 miles (40 km) from Reykjavík, Iceland.

The geologists’ findings were published on September 14 in the journal Nature.

10,000 Years in a Month

Thanks to a sabbatical, a pandemic, and 780 years of melting subterranean rock, Jackson was in the right place and time to witness the birth of Fagradalsfjall, a fissure in the lowlands of southwest Iceland that split and exploded with magma in March 2021. By that time, everyone on the Reykjanes Peninsula was ready for some kind of eruption, he said.

“The earthquake swarm was intense,” he said of the 50,000 or so temblors — some magnitude 4 and higher — that shook the earth for weeks and kept most of Iceland’s population on edge.

However, the sleep deprivation was worth it, and crankiness soon turned into fascination as lava bubbled up and spattered from the hole in the ground of the relatively empty Geldingadalur region. Both scientists and visitors alike flocked to the area to see the newest section of the Earth’s crust form. From the start, they were able to get close enough to sample the lava continuously, due to the lava’s slow flow and ample winds that blew the noxious gases away.

Volcanic eruption of Mount Fagradalsfjall in Iceland.

Led by Sæmundur Halldórsson at the University of Iceland, the geologists were trying to find out “how deep in the mantle the magma originated, how far beneath the surface it was stored before the eruption, and what was happening in the reservoir both before and during the eruption.” Questions like these, though fundamental, are actually some of the biggest challenges for those who study volcanoes. This is due to the unpredictability of the eruptions, the danger and extreme conditions, and the remoteness and inaccessibility of many active sites.

“The assumption was that a magma chamber fills up slowly over time, and the magma becomes well mixed,” Jackson explained. “And then it drains over the course of the eruption.” As a result of this well-defined two-step process, he added, those studying volcanic eruptions do not expect to see significant changes in the chemical composition of the magma as it flows out of the earth.

“This is what we see at Mount Kīlauea, in Hawaii,” he said. “You’ll have eruptions that go on for years, and there will be minor changes over time.

“But in Iceland, there was more than a factor of 1,000 higher rates of change for key chemical indicators,” Jackson continued. “In a month, the Fagradalsfjall eruption showed more compositional variability than the Kīlauea eruptions showed in decades. The total range of chemical compositions that were sampled at this eruption over the course of the first-month span the entire range that has ever erupted in southwest Iceland in the last 10,000 years.”

Night view of a volcanic eruption at Mount Fagradalsfjall in Iceland.

This variability is a result of subsequent batches of magma flowing into the chamber from deeper in the mantle, according to the scientists.

“Picture a lava lamp in your mind,” Jackson said. “You have a hot lightbulb at the bottom, it heats up a blob and the blob rises, cools, and then sinks. We can think of the Earth’s mantle — from the top of the core to under the tectonic plates — operating much like a lava lamp.” He went on to explain that as the heat causes regions of the mantle to rise and plumes form and move buoyantly upward toward the surface, molten rock from these plumes accumulates in chambers and crystallizes, gases escape through the crust, and the pressure builds until the magma finds a way to escape.

“Just when I think we’ve gotten close to figuring out how these volcanoes work, we get a big surprise.” — Matthew Jackson

As described in the paper, what erupted for the first few weeks was the expected “depleted” magma type that had been accumulating in the reservoir, which is located about 10 miles (16 km) below the surface. However, by April, evidence showed that the chamber was being recharged by deeper, “enriched” type melts with a different composition. These were sourced from a different region of the upwelling mantle plume beneath Iceland. This new magma had a less modified chemical composition, with a higher magnesium content and a higher proportion of carbon dioxide gas. This indicated that fewer gases from this deeper magma had escaped. By May, the magma that dominated the flow was the deeper, enriched type. These rapid, extreme changes in magma composition at a plume-fed hotspot, they say, “have never before been observed in near real-time.”

However, Jackson said that these changes in composition may not be so rare. It’s just that opportunities to sample eruptions at such an early stage are not common. For example, prior to the 2021 Fagradalsfjall eruption, the most recent eruptions on Iceland’s Reykjanes peninsula occurred eight centuries ago. He suspects that this new activity signals the start of a new, possibly centuries-long volcanic cycle in southwest Iceland.

“We often don’t have a record of the first stages of most eruptions because these get buried by lava flows from the later stages,” he said. This project, according to the researchers, allowed them to see for the first time a phenomenon that was thought to be possible but had never been witnessed directly.

For the scientists, this result presents a “key constraint” in how models of volcanoes around the world will be built. However, it is not yet clear how representative this phenomenon is of other volcanoes, or what role it plays in triggering an eruption. For Jackson, it’s a reminder that the Earth still has secrets to yield.

“So when I go out to sample an old lava flow, or when I read or write papers in the future,” he said, “it’ll always be on my mind: This might not be the complete story of the eruption.”

Reference: “Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland” by Sæmundur A. Halldórsson, Edward W. Marshall, Alberto Caracciolo, Simon Matthews, Enikő Bali, Maja B. Rasmussen, Eemu Ranta, Jóhann Gunnarsson Robin, Guðmundur H. Guðfinnsson, Olgeir Sigmarsson, John Maclennan, Matthew G. Jackson, Martin J. Whitehouse, Heejin Jeon, Quinten H. A. van der Meer, Geoffrey K. Mibei, Maarit H. Kalliokoski, Maria M. Repczynska, Rebekka Hlín Rúnarsdóttir, Gylfi Sigurðsson, Melissa Anne Pfeffer, Samuel W. Scott, Ríkey Kjartansdóttir, Barbara I. Kleine, Clive Oppenheimer, Alessandro Aiuppa, Evgenia Ilyinskaya, Marcello Bitetto, Gaetano Giudice and Andri Stefánsson, 14 September 2022, Nature.
DOI: 10.1038/s41586-022-04981-x


View Comments

  • The biggest question about this article is what creates the energy that makes volcanoes work. Is it fusion, the reaction that scientists have never gotten to produce energy? How is that going to produce a volcano from 4 thousand miles away?

    It is hard for science to understand how our planet works when scientists think it was created from a cloud of gas and dust. This cloud and gravity alone are not going to be able to create liquid rock spewing from the surface 5 billion years after the planet was created.

    Our planet was created out of a mass of quark plasma which is exactly what black holes are made of. Quark plasma is what is responsible for all the energy we see that has been around for billions of years. Fusion and gravity have nothing to do with anything which is made clear since the scientific community has no idea how either truly work.

    The scientists in this article need to realize that the "Big Bang" was merely our universe turning itself into a gargantuan particle collider when two, giant objects collided at an astronomical speed in an already existing, static universe. Our galaxy was one mass of quark plasma, our solar system was then one, and even our planets and corresponding moons and rings were initially single masses of quark plasma. This plasma is optically invisible and can make shapes. Quark plasma has created all the orbits that we see in the universe. This plasma creates all the naturally occurring elements all by itself as well starting from the outside surface of the black hole inward. The quarks use space itself as the catalyst and use space to give the density back to the quarks. First, the quarks and sterile electron neutrinos that make up space fuse to give the black hole the first neutrons it will ever possess. The beta minus decay reaction continues to create heavier elements using the quark plasma as the endless energy supply to create the nucleosynthesis.

    The only way scientists are going to understand the observations they make is to use a theory that a Tually follows the laws of physics it should. Current theories completely ridicule the laws but nobody seems to be able to blame the theory that has been used for nearly a century that explains absolutely nothing. My theory explained above is the "Theory of Everything" science seeks. If the Big Bang theory continues to be considered a fact, no progress will ever be made in physics or astrophysics.

    • Fusion? Whoever is Responsible for Volcanoes, Earthquakes, Floods, Tsunamis and Pandemics should be Punished Very Severely. We have punishments for Humans, Right? Humans are Super Supreme with Brains; But, SEVERAL Animals excel us in Several respects too ! I see a 1-month old Rhesus Monkey Infant jumping onto a Wall without any planning. We can't do such simple things. Salute to youtube.

    • A lot of misinformation in your comment. Fusion is what happens with light elements in the cores of stars. The Earth has residual heat from its original formation and subsequent bombardment by bolides. But, to the dismay of Lord Kelvin, his estimate of the Earth's age, based on temperature, was wrong because he wasn't aware of the heat contributed by the decay of radioactive elements.

      I suggest that you get yourself a modern textbook on geology, and read it.

  • Sea Water of Oceans is getting Dirty because of the lava flow; So, just keep dropping a couple of barrels of sea water into the Volcanoes EVERYDAY. If it causes a bad result, Stop it ASAP. Helicopters etc., are out there. Don't just sit quiet. Start something. We are spreading Wild Animals all over the world and letting lava flow into precious sea water. So much for Scientists Corrupted by the Dumb Politicians.

University of California - Santa Barbara

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