Geochemical Revelations

The geophysical techniques scientists are using to take the pulse of Svartsengi’s magmatic heart aren’t just tracking the hazard in real time. They’re also helping to construct a picture of the arteries that funnel all that magma to the surface — which is crucial for understanding the entire peninsula and how it might behave on longer time frames.

Fagradalsfjall and Svartsengi — the two currently active volcanic systems — are separated by just a few miles. Despite their proximity, geologic evidence strongly suggests that they are distinct systems. Their subterranean architectures are manifestly different. At Fagradalsfjall, magma rushes from the mantle straight to the surface, while at Svartsengi, it’s temporarily stored in the shallow crust.

And yet, puzzlingly, the two systems seem to draw material from the same source in Earth’s mantle, suggesting a deep connection.

Ed Marshall, a geochemist at the University of Iceland, has studied freshly scooped lava from eruptions at both sites to try to determine how the two volcanic systems are connected and why they’ve been taking turns erupting. “You want to park in a place where the gas and lava aren’t going to take you out,” he said. Then “you walk in, you scoop the sample, and you get the heck out.”

In general, Icelandic lavas display similar chemical patterns. But “Fagradalsfjall has the world’s weirdest melt chemistry,” Marshall said, referring to the specific mixture of elements and compounds that make up its magmatic soup. “It’s actually not just weird. It’s unique.” Unique, that is, except that the Svartsengi lava has almost exactly the same chemical fingerprints, even though Fagradalsfjall and Svartsengi are seemingly independent volcanic systems. “That makes absolutely no sense,” Marshall said. “Nature’s just messing with us at this point.”

But “if things are physically connected at depth,” he said, “that’s a pretty elegant solution to the whole problem.”

Seismic analysis of the peninsula’s volcanism is ongoing. Scientists hope to be able to forecast where it will emerge next in the coming months and years, as they did with the recent eruptions. As a start, Halldór Geirsson, a geophysicist at the University of Iceland, and his colleagues are using satellite radar to map faults and fractures on the peninsula during this period of unrest, which they suggest can reveal hidden faults, including those that may be the sites of future fissure eruptions.

There’s no guarantee that subsequent eruptions will follow the same pattern as Svartsengi’s recent outbursts — the sill-dike heart of the system is not necessarily a fixed feature. “Every time you have an eruption, you change the plumbing system. It doesn’t reset back to zero,” Mitchell said.

Grindavík’s future habitability is an open question, and it remains to be seen whether the peninsula’s other towns will be confronted with torrents of lava. Reykjanes Peninsula’s new hypervolcanic era has just begun, and it could last years, decades, perhaps even centuries.

“Unfortunately, there’s no good news ahead,” Jónsdóttir said.