Science | February 21, 2024

Iceland’s Recent Volcanic Eruptions Are Unleashing Deep Secrets

Each dramatic episode over the past few years has led to fresh geologic revelations, and researchers think another bout is on the way

A volcanic eruption moves toward the outskirts of the evacuated town of Grindavik on Iceland’s Reykjanes Peninsula. Icelandic Department of Civil Protection and Emergency Management / AFP via Getty Images

Maya Wei-Haas

Reporter

An eruption cracked through the silence of night last December 18 as molten rock burst from the ground of Iceland’s Reykjanes Peninsula. Moments later, Celine Lucie Mandon’s phone rang, rousing her from near-sleep to alert her of the blast. Around 2 a.m., Mandon, a gas geochemist at the University of Iceland, and three of her colleagues stood before the incandescent fountains of lava, which bathed the snowy landscape and cloud-streaked skies in an otherworldly crimson glow.

“It was completely surreal, that color,” Mandon says. While they had brought headlamps, the group quickly realized artificial light was unnecessary. Illuminated by the molten rock’s radiance, the group delved into the purpose of their late-night venture: collecting lava samples and measuring volcanic gasses.

These efforts are just one part of the enormous push to study the many recent eruptions on the Reykjanes Peninsula. The region’s volcanoes had slumbered for almost 800 years, but they awoke with a roar in 2021 during the Fagradalsfjall eruption. For nearly six months, lava poured from a fissure roughly 3 miles east of December’s blast, steadily filling the valley with molten rock. Now, with six eruptions rocking the Reykjanes in just three years, scientists suspect the peninsula has entered a new period of volcanic activity—the beginning of possibly centuries of geologic unrest.

Each eruption provides glimpses into the deep, giving researchers a detailed understanding of the volcanic processes transpiring far below the surface. These insights help them suss out the origins of the magma, how the volcanic system evolved over time and more.

These studies are also unearthing unexpected chemical similarities between the lavas of each eruption that hint at deep subsurface connections across the peninsula. “This is very surprising,” says Edward Marshall, a geochemist at the University of Iceland, who is studying the chemical conundrum. “Volcanoes pop up in different places—they’re not supposed to talk to each other.”

But amid the scientific excitement are also concerns for the future of the people living in the region. While the early spurts of volcanism struck in unpopulated regions, the eruptions this winter broke through the ground just north of the town of Grindavik, home to some 3,800 people, and near the Svartsengi power plant, which supplies water and electricity to most of the Reykjanes, a peninsula spanning roughly 772 square miles. The most recent eruption, on February 8, gushed lava from a fissure nearly two miles long in a similar region as the December eruption, cutting off hot water for thousands of residents. While the volcano’s roar quieted the following day, magma soon began accumulating again. Another eruption is likely by the end of February or early March, according to modeling from the Icelandic Meteorological Office.

Eruptions in Iceland are the norm, as the island itself was forged from volcanic fire. The country is one of the only places in the world where the mid-ocean ridge stands above the waves. Here, the Eurasian and North American plates gradually draw away from one another, sending molten rock welling up from the deep to erupt at the surface. In the southeast of the island, the ridge coincides with a searing hot column of molten rock, known as a hot spot, which drives even more volcanic fury.

In the Reykjanes Peninsula, which is located far from the hot spot, the plates are tugged at an angle, which forms a series of fissures that cut into the ground across the land and direct magma as it oozes toward the surface. Rather than volcanic eruptions from a central peak, volcanoes of the Reykjanes often fountain from these fissures, creating floods of molten rock that look a bit like tiger stripes on a map.

Lave Erupts on the Reykjanes Peninsula — Lava erupts from a fissure on the Reykjanes Peninsula, almost two miles north of Grindavik. Kristinn Magnusson / AFP via Getty Images

The last period of volcanic activity on the Reykjanes struck between 800 to 1240 C.E., when volcanic spurts—known as fires—sporadically burst from the land. Since that time, however, the volcanoes of the Reykjanes have fallen silent. But in late 2019, earthquakes began rattling through the central peninsula. The rumbles dragged on for over a year, with more than 17,000 recorded in the first week of March alone. Swaths of the ground also began to deform, a telltale sign that magma was building underground. But then, the system quieted.

“We thought, OK, maybe this is it. We’re not going to see an eruption this time,” Kristín Jónsdóttir, a seismologist at the Icelandic Meteorological Office, tells CBS News. “But we were wrong.”

On the evening of March 19, 2021, the Reykjanes finally rumbled to life. Lava gushed across the landscape near Fagradalsfjall mountain, the first of many eruptions. In August 2022, lava filled a nearby valley during the Meradalir eruption, barely half a mile away. Then in July 2023, lava spurted from a half-mile-long crack at a site named Litli-Hrutur just northeast of the two earlier eruptions.

Then came December’s eruption that burst from a fissure about 2.5 miles northeast of Grindavik, sending lava hundreds of feet into the air. While concern rose for the town’s residents, the event lasted just three days. The morning of January 14, lava breached the surface even closer to town. Much of the molten rock was diverted by a defensive wall that had been erected in the wake of the December eruption. But that afternoon, residents’ worst fears were realized when a fracture opened up south of the wall at the edge of town. In a scene seemingly straight from a disaster flick, lava oozed into the city. Workers who had been erecting new defensive barriers narrowly escaped with their equipment as the walls of fire closed in.

Thankfully the eruption was short-lived. Only a few structures burned, and no lives were lost. But it was a reminder that while many of the earlier eruptions were far from populations, Reykjanes’ new period of volcanic activity holds many risks. “We’ll watch in slow motion as Iceland rearranges itself to go back into a period of natural hazard hardship,” Marshall says.

Lava Spews From a Fissure on Reykjanes — Lava spews from a fissure on Reykjanes in January 2024. Icelandic Coast Guard via Getty Images

Lava runs through Icelanders’ veins from their earliest history. The Norse settled in Iceland during the last period of intense volcanism in the late 800s. One famous story from this time, around 1000 C.E., recounts the parliament’s discussion of becoming a Christian nation, says Halldór Geirsson, a geophysicist at the University of Iceland. Opponents of the idea pointed to the active eruption as evidence that they had angered the Norse gods. Others countered that there were many more ancient flows of lava from times before people set foot in the region.

Scientists now know plenty more about how and why volcanoes erupt. Yet the origin of the Reykjanes’ cyclicity of volcanic activity every thousand or so years remains unknown. The pattern is not easy to study, Geirsson emphasizes. Only the last three or four cycles can be seen at the surface, so it’s uncertain if they continued further back in time. Each new spasm of volcanic activity lays a fresh layer of volcanic rock, burying evidence of past eruptions. “Geological history is always overriding itself,” he says.

Yet clues to what’s happening deep underground may be found in the curious patterns that emerged during eruptive periods. For example, the Reykjanes eruptions seem to take turns: If one volcanic system is inflating, then the others lay quiet. “Only one system sort of has the ball at the time,” Geirsson says.

The pattern hints at a deep connectivity of the system, an idea further bolstered by recent geochemical analyses. The lava that erupted in 2021 had a “weird, freaky composition,” enriched in what are known as incompatible elements, Marshall says. This chemistry gives the molten rock a unique chemical fingerprint that can act like a tracer. They spotted this fingerprint during the 2022 eruption, then again in 2023, and twice more in 2024—appearances that all hint at the sharing of magma deep underground.

“We can go and see it popping up all over,” Marshall says. “It’s this marvelous natural experiment.”

Exactly how this sharing of magma happens, however, remains uncertain, but the answer might be a key to understanding the 1,000-year cycles of volcanic activity. One possibility is that a multitude of little pockets of magma lingers deep underground, slowly filling as molten rock trickles in, Marshall explains. As these blobs of magma swell, they form new connections, shifting and merging into larger reservoirs that can eventually erupt at the surface. Another possibility is a “magma surge” in which a tsunami of molten rock floods up from the mantle into the subsurface, awakening volcanoes across the peninsula, Geirsson explains.

Many unknowns linger, Marshall says. But answers may soon be on the horizon. Marshall and his colleagues are working on the challenging task of dating when the magma formed, which would help them uncover how long the molten rock lingered in the mantle before emerging at the surface.

Each new eruption also promises to bring fresh revelations that could help scientists better understand future volcanic hazards. So while the potential for future eruptions is high, so too is the promise for future discoveries. “Iceland is a unique setting where we get to see processes happen unveiled, in a way, where in most places they’re always veiled,” Marshall says.