Scientists discover massive fan-shaped geological structure beneath Antarctic ice

Three kilometers down through Antarctic ice, beneath layers of compacted snow that have accumulated over millennia, researchers have found something that was never supposed to be there—or rather, something that has always been there but remained invisible until now. A team of geoscientists drilled deep into the frozen continent and discovered a vast fan-shaped geological structure, a network of thirty subglacial basins arranged in a pattern so coherent and so large that it rewrites what we thought we knew about Antarctica's ancient past.

The discovery, published in Nature Geoscience on June 3rd, describes what the researchers have named the Eastern Antarctic Fan-Shaped Basin Province. What makes this finding extraordinary is not just its scale but what it reveals about the deep time of our planet. The structure appears to be a record of continental forces at work before Gondwana—the ancient supercontinent that included Antarctica, Australia, Africa, and South America—broke apart. The basins radiate outward like the ribs of an open hand from a single focal point near the South Pole, at coordinates 86.4 degrees south and 129.9 degrees east. This focal point, known in geology as a pole of Euler, acts as the pivot around which the entire system seems to have rotated.

Using subglacial topography and geophysical data, the scientists mapped thirty V-shaped basins that together form what they describe as a previously unrecognized coherent unit. The structure stretches across an enormous region, from Prydz Bay to the Transantarctic Mountains. The researchers propose that this landscape was created by rotational extension—a kind of continental stretching and twisting—that occurred before Gondwana fragmented. The process, they suggest, divided the region into two sectors: one on the western side showing left-lateral movement, the other on the east showing right-lateral movement, separated by what they call the Belgica Bisector.

What makes this discovery more than an academic curiosity is that it explains features of Antarctica that have long puzzled geologists. The rotational forces that created the fan-shaped basins had three major consequences across the continent. To the west, they generated compression that lifted the Gamburtsev Mountains, giving them their surprisingly young appearance for such ancient terrain. To the east, the same forces rotated the northern segment of the Transantarctic Mountains by roughly twenty degrees clockwise, fragmenting them into three tectonic blocks and forcing them upward through a process involving thermal buoyancy. To the north, the edge of the fan created a zone of weakness in the lithosphere that ultimately controlled where Antarctica and Australia separated, shaping the semicircular passive continental margins visible today.

But the significance of this ancient structure extends into the present. The basins and their boundaries have guided the flow of ice streams and shaped the subglacial landscape in ways that continue to matter. The great outlet glaciers—Totten, Denman, and Amery—developed along pathways established by these ancient geological features. The deep valleys that channel ice toward the ocean follow the grain of structures laid down hundreds of millions of years ago.

There is a climate dimension to this discovery that gives it urgent relevance. Because of the way these basins subsided over geological time, large portions of them now lie below sea level. This means the ice sheet resting above them sits on bedrock that is submerged, making it more vulnerable to warming ocean water. As the climate changes and sea levels respond, these below-sea-level basins become potential weak points where the ice sheet could thin or collapse more readily. The ancient geological architecture that shaped Antarctica's mountains and valleys now influences how the continent's ice will respond to the warming world.