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KRAFLA VOLCANO IN ICELAND—After years of effort, volcanologists are ready to open a gateway to hell. From the rim of the Víti (“hell” in Icelandic) crater—a smaller crater within Krafla’s 10-kilometer caldera—Ottó Elíasson looks down on at a tranquil grassy field disturbed only by a spindly weather station. That will change soon, says Elíasson, science chief at Eimur, a geothermal research center. “Ten years from now, this could be the center of volcanology.”

The main attraction lies 2 kilometers below this spot on this volcanically hyperactive island, which is being split in two by the spreading Mid-Atlantic Ridge. In 2009, drillers trying to tap hot water for geothermal energy here accidentally pierced a hidden magma chamber. After an outpouring of steam and glass shards from quenched magma, the borehole created the hottest geothermal well ever measured—until the casing failed.

Now, researchers are returning to penetrate the molten rock on purpose, using hardier equipment, to create the world’s only long-term magma observatory. “We’ve been to Mars. We’ve been to Venus,” says Paolo Papale, research director at Italy’s National Institute of Geophysics and Volcanology. “But we have never observed magma below the Earth’s surface.” Results could help explain how magma moves through the crust, while improving eruption forecasts. They could also shed light on how the continents formed and grew.

In May, the Krafla Magma Testbed (KMT) received financing from the International Continental Scientific Drilling Program, which said the project was one of its top priorities for the decade. With that support, along with several million dollars in funding from Iceland and other European science agencies, the project this month entered its preparation phase. It will prove out the technologies needed to hold the well open despite the corrosion that comes with superheated water, take geophysical soundings of the magma chamber, and model how the chamber will behave once penetrated. The first borehole, costing as much as $25 million, could begin as soon as 2023.

Unable to study magma directly, volcanologists rely on surface measurements from seismometers, GPS sensors, and radar satellites to guess its movements. They can examine solidified magma chambers exhumed by Earth’s upheavals—but those remnants are incomplete, selectively depleted by ancient lava flows. They can study lava at the surface, but the samples have by then lost most of the trapped gases that drive eruptions and influence the magma’s original temperature, pressure, and composition. Crystals, inclusions, and bubbles in the hardened lava hold clues to its original state. But a sample from the Krafla chamber will tell researchers whether those estimates “are fictional or reliable,” says John Eichelberger, a volcanologist at Southern Methodist University and KMT leader.

Island of fire and ice

Riven by tectonic plates, Iceland hosts many active volcanoes. At Krafla, magma is close to the surface.

Map of Iceland and tectonic plates text

Getting a sample will also reveal the true nature of the magma chamber. Most scientists reject the cartoonish view of magma chambers as hellish underground lakes. “We think of these systems as a mush”—small amounts of liquid between crystallized grains—“rather than a liquid balloon,” says Marie Edmonds, a petrologist at the University of Cambridge.

But Krafla, which last erupted in 1984, may be an exception. The glassy bits from the 2009 drilling campaign hinted that the magma was not only liquid, but also circulating, interacting with melt lower down. “That’s the most shocking thing from what little we’ve gleaned so far,” Eichelberger says. But little is known about the magma chamber’s size or how long it has persisted—questions KMT can help answer. “It’s seeing through a glass darkly, as it were,” Eichelberger says.

KMT will also help answer basic questions about the raw material of continental crust. The world’s sea floors, and much of Iceland, take shape from basaltic magma—much the same stuff that exists in the mantle. But the granite rocks of the continents form from a stickier, silica-rich “rhyolitic” magma that is thought to lie below the KMT site. No one is sure how the continent-forming magma originates; one idea is that basaltic magma gets altered by seawater, remelts, and eventually erupts from volcanoes as rhyolite. Samples of rhyolite from basalt-dominated Iceland could provide a window on how this process works worldwide, Eichelberger says.

KMT intends to collect multiple samples over time and embed sensors in and near the magma to measure heat, pressure, and even chemistry despite temperatures of more than 1000°C. “The technical challenges are formidable,” says Wendy Bohrson, a volcanologist at the Colorado School of Mines. KMT’s drilling partners are testing flexible couplings that can allow the steel liner of the well to expand and contract with extreme heat. And others are developing innovative electronics to withstand the heat and pressure, which could someday be used on Venus.

The technologies could also benefit Iceland’s many geothermal energy companies, which have shied away from the hottest rock. Getting closer to magma could dramatically increase the power potential of individual wells—as was clearly seen with the accidental 2009 well, which on its own could have powered a small city. “The geothermal industry is really looking to understand the real source of its energy,” says Hjalti Páll Ingólfsson, managing director of Iceland’s Geothermal Research Cluster.

The large amounts of water injected to cool and lubricate the drill will likely perturb the volcanic system a bit, and geophysicists will be watching closely. (There is little worry of triggering an eruption, given the mild behavior of the 2009 borehole, but the site’s remote, uninhabited location is another selling point.) Changes in the speed of seismic waves after drilling could reveal the magma’s extent, Papale says. Watching these subtle changes could also help with predicting future rhyolite eruptions. Although scientists have gotten quite good at detecting a volcano’s warning signs, false alarms abound.

And if KMT remains in place, scientists will eventually get to watch an eruption in action—from the perspective of the underground source of magma. “That will be gold,” says Yan Lavallee, a volcanologist at the University of Liverpool. “It is bound to happen.”

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