After being shaken by 15 months of increasingly disruptive earthquakes, including about 50,000 in the past three weeks, Iceland’s Reykjanes Peninsula is finally experiencing the volcanic eruption that many geologists suspected was on its way. After nearly 800 years without an eruption, this southwestern strip of the country is experiencing lava flows that experts say have been a long time coming.
On Friday, March 19, at around 8:45 p.m. local time, molten rock breached the surface in a valley near a flat-topped mountain named Fagradalsfjall, in the region of Geldingadalur, six miles from the nearest town. Incandescent spatter erupted along a crack in the earth, scorching the soil as small lava fountains illuminated the dark landscape.
The eruption involves a relatively small amount of lava confined to a series of valleys, making it unlikely that any population centers will be threatened. This type of molten rock is very fluid and trapped gasses easily escape, and it’s not erupting into water or ice, so it won’t become especially explosive, generate a sustained ash plume, or fling any sizable volcanic blocks across the region. Scientists believe the eruption will persist for a few more days or weeks before fizzling out.
But this modest eruption could mark the beginning of something bigger. Evidence from both historical accounts and ancient lava flows shows that whenever this region has experienced a major uptick in seismic activity, intermittent eruptions followed for around 100 years.
“The signs are that it’s reawakening,” says Dave McGarvie, a volcanologist at Lancaster University.
The Geldingadalur eruption therefore provides an unprecedented opportunity to study the long-term volcanic activity of southwest Iceland. Scientists are scrambling to monitor what may be the opening salvo in a series of volcanic volleys, which could provide clues about why the peninsula flares up just once every eight centuries.
The case of the missing magma
Sitting on a landward portion of the continuously spreading Mid-Atlantic Ridge, the Reykjanes Peninsula, about 17 miles southwest of the capital city Reykjavík, is no stranger to earthquakes. But since late 2019, temblors have become more frequent and more energetic. Icelanders on the peninsula, particularly those in the coastal town of Grindavík, have had trouble sleeping lately due to the constant shaking.
This heightened seismic activity is thought to represent a transition from a gradual opening of the rift to a considerably more dramatic phase when both sides of the peninsula are rapidly pulled apart. When a geologic rift quickly pulls the land apart like this, it creates an empty space, and magma rushes up to fill it in.
On March 3, acoustic signals associated with the injection of magma into the shallow crust emanated from between the mountain Fagradalsfjall and a series of fissures that erupted long ago. A new eruption seemed extremely likely—but no lava followed, and the acoustic signals vanished, says Thorbjörg Ágústsdóttir, a seismologist at Iceland GeoSurvey.
Instead, the sheet of magma, known as a dyke, wandered about underground for the next few weeks. Seismic activity and the changing shape of the ground allowed scientists to roughly track its movements. They caught it oscillating between the northeast and southwest of the peninsula, causing cracks to appear in the earth above as it went.
“I called it the dithering dyke because it didn’t seem to know what to do,” McGarvie says. It appeared to be searching, to no avail, for a place it could breach the surface.
Over the past few weeks, the seismic activity in the region declined, and most dykes cool and solidify before getting a chance to erupt. This led some scientists to suspect an eruption would not occur after all.
Iceland’s uppermost crust is peculiar, however, acting somewhat elastically—meaning it’s a little closer to toffee than hard candy. The crust in this area can stretch a little to make room for magma, allowing the dyke to infiltrate the rock just below the surface without causing violent fractures and producing those telltale acoustic signals.
This stealth mode is typical for eruptions that happen along fissures, such as those along the peninsula. Scientists in Iceland had “just been in the field, and all of a sudden, the ground is opening,” Ágústsdóttir says. Apparently the waning seismic activity in this region, instead of being a sign of calmer days to come, could in fact be a precursor to an eruption.
A long-awaited eruption
On March 19, the Icelandic Meteorological Office picked up a few low-frequency earthquakes that may have come from magma moving toward the surface—but these were very subtle events, Ágústsdóttir says. With no way to know when and where an eruption would happen, local authorities continued to tell people to stay away from the fissure-riddled area.
That evening, lava began erupting close to Fagradalsfjall, inside Geldingadalur, a natural depression whose name means Eunuch Valley—possibly a reference to early settlers’ practice of castrating animals in the region. After failing to find an escape hatch to the northeast or southwest, the dyke apparently “broke through in the middle, because both directions were kind of jammed,” says Tobias Dürig, a volcanologist at the University of Iceland.
Lava first poured out of a meandering fissure 1,650 feet long, but over the weekend, the eruption focused its output on single spot, building a steep, towering cauldron of freshly cooled rock. Smooth rivers of lava crept around blockier, rubble-like lava. Lava flowing at a steady pace caused the cone to suffer a few partial collapses as it flung blobs of lava across the scorched earth.
The dyke of magma is small, just over four miles long, and the eruption is confined to a valley that is surrounded by more valleys, preventing lava from escaping the area and threatening any population centers. Sulfur dioxide, a common volcanic gas, is being emitted by the eruption, however, and even small quantities can irritate the lungs of those with respiratory conditions such as asthma. But so far, the wind is blowing the volcanic gas away from populated areas.
Scientists say one possible concern is that a new fissure could suddenly and unexpectedly open up near the current one, ambushing anyone in the area. “That could easily happen, and that could happen fast, and it would not be a good place to be,” Dürig says.
Studying the inferno
Overall, however, scientists believe this will be a largely unhazardous eruption. Thanks to easy access to the area, researchers are throwing their entire toolbox at the eruption, seeing it as the best chance they have ever had to understand the unusual tectonics and volcanism of the region.
Some have scooped up lava and rushed it to a lab, hoping to unravel the specific chemistry of the material. Dürig has flown back and forth over the eruption, using radar to determine how thick the lava flows are and estimate how much lava is erupting.
“It’s a very special thing to get close to an eruption site,” Ilyinskaya says. During the eruption’s beginning, she was greeted with a cacophony of booms and whooshes under her feet. “It shakes you to your core,” she says. “This is something that’s really, really powerful. You feel very small and very insignificant.”
Against official advice, thousands of people living in the peninsula have gathered around the eruption site, treating the ridges as an amphitheater. One group lingered for too long, then got lost looking for their cars in the dark. Someone was also caught trying to fry eggs and bacon atop the lava, predictably with little success.
While volcanologists are taking the opportunity to study this eruption, archaeologists are scrambling to figure out if the lava threatens any significant sites. Based on historical records, experts believe a burial site thought to date back more than 1,000 years, perhaps belonging to a notable figure, could be right in the path of the eruption. According to local news reports, archaeologist Oddgeir Isaksen of the Cultural Heritage Agency of Iceland sped to the scene in a helicopter shortly after the eruption began, but he was not able to find evidence of the burial site before lava overran the area.
A century of activity?
The eruption is probably going to peter out in the coming days or weeks, and the bigger earthquakes keeping people awake may also drop off for a bit. “A small eruption still releases some pressure,” Ágústsdóttir says.
But there are hints that the fireworks are far from over. “The amount of seismic energy release for this small eruption is disproportionately high,” McGarvie says. There could have been a significant amount of tectonic shifting across the peninsula, meaning additional pockets of magma could make their way to the surface.
Based on the geological history of the region and studies of somewhat similar eruptions elsewhere in Iceland, another eruption from a different fissure in Reykjanes Peninsula is a distinct possibility, Ilyinskaya says. But this could transpire in days, weeks, months, or even years. It may involve a similar amount of magma as the current eruption, or it could release significantly more.
The possibility of future eruptions is underscored by the fact that the type of seismic shaking leading up to last week’s eruption has happened before—three times before, in fact, in the past few thousand years. Historical accounts and layers of ancient volcanic rock suggest that each time this area experiences a significant increase in earthquakes, it culminates in several decades of eruptions, jumping from fissure to fissure all over the peninsula.
The small and relatively safe eruption occurring now therefore provides a stellar opportunity for scientists and emergency managers to prepare for possible bursts of lava to come. “If this is the start,” Ágústsdóttir says, “this is good training.”