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When Quiet Undersea Volcanoes Turn Disruptive
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geophysics
When Quiet Undersea Volcanoes Turn Disruptive
By
Evan Howell
May 26, 2026
Earth’s largest volcanic system, hidden in mountain chains under the sea, has long been assumed to erupt only quietly. The shallow seafloor off Iceland tells another story.
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Rock formations emerge from the waves along the shore of Iceland.
Jonas Preine
Introduction
By Evan Howell
Contributing Author
May 26, 2026
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earth science
geology
geophysics
physics
volcanoes
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Jonas Preine, a recently minted Ph.D. from the University of Hamburg, squinted at a computer screen in the lab of a ship as it bobbed in the North Atlantic near Iceland. The image before him just didn’t make sense.
It was June 2024, and Preine was among a crew of scientists who had set off from Reykjavik under slate-colored skies, trading their regular lives — family, friends, and the typical office environment — for cramped quarters and nausea on board the Meteor, a research vessel chartered for Expedition M201. They’d been lucky so far, enjoying relatively calm seas as they motored toward their destination, an unexplored deep-water basin dotted with volcanic shapes. The researchers carried reams of equipment: geophysical tools to collect seismic profiles of the Earth’s interior, cameras to image the ocean floor, and coring and dredging equipment to sample rocks and verify what might appear in grainy, partially processed computer images.
That first evening, about 100 kilometers from port, the team paused to test their geophysical tools in shallow waters. The seismic imagery they collected of the seafloor’s layered interior would lead them to an unexpected discovery, one that would complicate what we know about the usually sluggish volcanic fissures that lace the bottom of the ocean. Their findings could also be connected to mysterious islands from the recesses of history that witnesses said appeared suddenly, only to disappear later beneath the waves.
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The Meteor transported the scientists on Expedition M201 to their research site off the coast of Iceland.
Jonas Preine
In the lab, Preine snapped some screenshots and shared them with the team. Six weeks later, on returning from the expedition, he needed little effort to convince the project’s lead scientist to stop in shallow waters to investigate what they’d found.
A Conveyor Belt of Lava
Iceland is a geological rarity. Here, on the world’s largest volcanic island, you can hike through gorges dividing the North American and Eurasian tectonic plates.
That’s because Iceland sits on a mid-ocean ridge, a vast seam where Earth’s crust tears apart and oceans grow in the expanding space between. The Mid-Atlantic Ridge began forming about 200 million years ago, as the supercontinent Pangaea broke apart at the end of the Triassic Period. Iceland emerged much later when a plume of unusually hot mantle rock arched the ridge up above the gathering waves.
Across the globe, mid-ocean ridges have a nondramatic style — nothing like Washington State’s explosive Mount St. Helens or southern Italy’s Mount Vesuvius, the destroyer of Pompeii and Herculaneum. So the team aboard the Meteor wasn’t expecting anything unusual when they passed over a submerged segment of the Mid-Atlantic Ridge called the Reykjanes Ridge. They just wanted to confirm that their equipment was in working order.
The crew switched the equipment on, pinging back X-ray-like images that revealed layers of the seafloor’s stone interior. “We decided to do two test profiles over the Reykjanes Ridge because it was logistically easy and potentially interesting,” said Preine, now a marine geophysicist at the National Oceanography Center in England.
In Iceland’s Thingvellir National Park, hikers can travel along a path between the North American and Eurasian tectonic plates.
mauritius images GmbH/Alamy
Seismic images of mid-ocean ridges typically show rough and jagged terrain, formed when lava oozes up into the cold ocean along faults or fissures and hardens suddenly into stone. But that’s not what Preine saw. Along the ridge were smooth mounds with steep sides and flat tops, their flanks draped in scattered...