Experts believed that anomaly was a lava lake, a rare scientific reaction where magma is able to survive above the Earth's surface.
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Dr. Emma Nicholson, volcanologist and National Geographic Explorer, has researched volcanoes in far off jungles and remote mountains. She's no fan of boats, but was still compelled to study the anomaly, even though the journey involved a long and dangerous sea voyage to a chain of uninhabited volcanic islands in the South Atlantic Ocean.
"South Sandwich Islands really are about as remote from anywhere as you can get," Nicholson said, "That remoteness adds an element of risk there. If anything goes wrong, nobody is coming to get you. You have to solve your own problems."
Glaciers covering Mount Michael's landscape are made extremely unstable by heat under the volcano. Previously, no one has ever managed to reach its summit.
"These islands are mostly monitored by a satellite because they are so incredibly difficult to get to," Nicholson said. "What we lacked was these ground-truth observations to kind of anchor what we were measuring by so satellite."
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What lies inside, the world's ninth lava lake, could provide new clues to help predict volcanic eruptions around the globe.
"Volcanoes around our planet pose a huge risk to our society," Nicholson said.
About 1 in 10 of the world's population live within the footprint of volcanic hazards, she explained. A volcanologist's role is reduce the exposure to volcanic risk and improve understanding of how volcanoes may transition into phases of eruption.
Dr. Nicholson said the best way to do that is to create on-site laboratories study volcanoes in person, even if the journey is dangerous.
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"There were so many points of possible failure along the way," she said. "Which makes any discovery that we could make that much sweeter, because at so many points, nature could have just said 'no.'"
You can learn more about lava lakes in Nat Geo's November issue.
National Geographic's latest special, "Explorer: Lake of Fire," is streaming now on Disney+.