Antarctica is a land of not only ice, but fire. More than 100 volcanoes hide beneath the ice sheet or poke through it. One, 3800-meter-high Mount Erebus, seethes menacingly just 40 kilometers from McMurdo Station, Antarctica’s biggest research base. Another, Mount Waesche, has yielded unsettling hints that ice loss triggered its ancient eruptions. Now, researchers are targeting both peaks to learn about immediate and long-term threats.
Sensors being installed this month along the rim of Erebus could help researchers understand the threat the wildly active volcano poses to McMurdo and New Zealand’s Scott Base next door. And a planned field campaign this month to Waesche will explore the possibility that climate change could reawaken ice-bound volcanoes, whose hot, eruptive bursts could in turn accelerate ice loss in a new, dangerous feedback. “It’s an interesting hazard,” says Matthew Zimmerer, a geochronologist at the New Mexico Institute of Mining and Technology (NMT).
Erebus is only a 20-minute helicopter ride from McMurdo, so since the 1960s scientists have studied the volcano and the lava lake that roils within its caldera, occasionally tossing out “bombs” of molten rock. Seismometers placed near the summit have revealed much about Erebus’s shallow magma plumbing. But high winds have deafened the instruments to the rumblings from deeper magma, says Rick Aster, a geophysicist at Colorado State University. “We’re looking into the tip of a magmatic system that extends perhaps 150 kilometers into the mantle.”
A small team flew to Erebus last month to begin burying a fresh set of seismometers where they will be protected from wind noise. It wasn’t easy: The half-ton compressor needed to drive the team’s large pneumatic drill was too heavy for their helicopter. So after acclimating to the thin air near the summit, technicians began to dig the first of four holes, each 1 meter deep, with shovels and a handheld drill. At lunch one day, the wind chill reached –59°C, says Glen Mattioli, vice president for instrumentation at the EarthScope Consortium, which operates the seismometer network.
Protected from the wind, the seismometers will transmit their data in real time and operate through the darkness of the Antarctic winter, allowing Erebus to be monitored continuously for hazards. They might also offer deeper insights.
Volcanoes rarely keep an open lava lake for long periods of time, let alone decades, as Erebus does. But when they do, it’s thought that the lake acts as a release valve, preventing pressure from building up. At Erebus, however, researchers have tracked long-term cycles of pressure buildup that perceptibly inflate and deflate its flanks, suggesting a gap in understanding how its magmatic plumbing works, says Ronni Grapenthin, a geophysicist at the University of Alaska Fairbanks.
The 20-meter-wide lava lake also holds puzzles of its own. Its churn can lead to giant gas bubbles that span the entire lake. When a bubble breaches the surface, it explodes, launching lava bombs that can land more than 1 kilometer away. Aster hopes the new seismic stations will reveal why the lava lake can shift from agitation to years of quiet and why, in earlier times, Erebus erupted more violently. A better understanding of its plumbing could also help guide models of other Antarctic volcanoes, Grapenthin says. “Erebus helps us understand what other volcanism in the region could look like.”
Waesche, meanwhile, though dormant and possibly extinct, may offer an answer to the most pressing question in Antarctic volcanology: With ice melting ever more quickly, will the volcanoes grow more active? The idea is simple: As the weight on the volcanoes is lifted, the gases trapped in magma are released like the fizz in an uncorked bottle of champagne, driving eruptions. Such a dynamic has been seen with volcanoes in Iceland and the U.S. Pacific Northwest, says Adelina Geyer, a volcanologist at Geosciences Barcelona. “As soon as glaciers start to retreat, volcanic activity starts to increase.” But no evidence of the interplay has been recorded in Antarctica.
Last decade, an NMT team made the arduous trip to Waesche, some 1500 kilometers from McMurdo, and sampled lavas from when it was last active, more than 100,000 years ago. Laboratory analyses, as yet unpublished, revealed the rocks came from more than 50 different eruptions, nearly 90% of which occurred between ice ages, when temperatures were warm, like today’s—and when ice sheets were presumably thin. “It was a totally unexpected correlation,” Zimmerer says.
This month, the researchers will return to Waesche, looking for more rocks that could confirm whether the loss of overlying ice caused Waesche to wake up. The team hopes to visit other volcanoes in the upcoming years to explore their response to ice melt.
Zimmerer says it’s unclear how fast volcanoes would respond to shrinking ice, if at all. And one volcano erupting under the ice wouldn’t cause much extra melting. But if many erupted, he says, a feedback loop could take hold, with ice loss leading to more volcanism, and more eruptions to more ice loss and consequent sea-level rise. If so, humanity’s greenhouse gas emissions can even affect the planet’s most remote volcanoes—which could in turn impact humanity’s fate.
More: https://www.science.org/content/article/could-melting-ice-wake-antarctica-s-volcanoes
