![\"\"](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/06\/bedrock-body.jpg\")
A map of Antarctica beneath the ice. (Pritchard et al., Sci. Data, 2025<\/a>)<\/p>\nThe researchers have named it the East Antarctic Fan-Shaped Basin Province (EAFBP), and they propose that it formed before the breakup of the Gondwana supercontinent, creating a zone of weakness that may later have helped steer the separation of Antarctica and Australia.<\/p>\n
And it may still be shaping Antarctica to this day.<\/p>\n
“Because these basins underlie about half of the East Antarctic Ice Sheet, they are likely to heavily influence both ice-flow and landscape evolution, making them essential to Antarctic glacial and hydrological processes,” the researchers write in their paper<\/a>.<\/p>\n The question about the shape of the land underlying Antarctica<\/a> isn’t purely an academic one.<\/p>\n That’s partially because the ice isn’t just sitting there; it’s moving, glacially, and that movement is guided by the contours of the bedrock. We can better predict the speed and direction of the flow if we have a detailed understanding of those contours.<\/p>\n The other big reason is that it’s a huge piece of Earth’s terrestrial history.<\/p>\n It makes up about 10 percent of Earth’s landmass<\/a>, and many questions about Gondwana, continental breakup, ancient mountain building, and crustal evolution have an Antarctica-shaped hole in them because we can’t directly see most of the continent.<\/p>\n Interestingly, the researchers did not set out to find a fan-shaped geological structure spanning a substantial proportion of Antarctica.<\/p>\n Rather, they were investigating what East Antarctica would look like if the ice were removed \u2013 which is not the same thing as what the radar images show under the ice.<\/p>\n There are an estimated 27 million cubic kilometers<\/a> of ice covering Antarctica, and it’s not just sitting there. All that mass pushes the bedrock downward. If the ice disappeared, the land would bounce upward<\/a>, gaining as much as a kilometer (0.6 miles) in altitude.<\/p>\n The researchers combined reconstructed rebound topography with radar, gravity, seismic, and magnetic data to investigate the buried landscape.<\/p>\n And, as they examined the reconstructed topography, they noticed something peculiar.<\/p>\n Many of the major subglacial basins in the area seemed to have the same basic geometry \u2013 not random depressions, but fanning outward from a common, central point near the South Pole \u2013 what they describe as a<\/a> “coherent continent-scale radial pattern”.<\/p>\n The geometry bears a striking resemblance to a type of tectonic feature known as a sphenochasm, described in 1955 as<\/a> “the triangular gap of oceanic crust separating two cratonic blocks with fault margins converging to a point, and interpreted as having originated by the rotation of one of the blocks with respect to the other.”<\/p>\n The researchers compiled a list of processes that could have sculpted the EAFBP from Antarctic bedrock. Several mechanisms can create large basins, including inherited structures, rifting, glacial erosion, and crustal stretching.<\/p>\n However, the radial arrangement of the Antarctic basins, together with patterns in crustal thickness and topography, matched most closely with a process known as rotational extension, in which the crust spreads outward from a pivot point like an opening handheld fan.<\/p>\n This becomes easier to appreciate when you look at the map, with ridges radiating outward like the ribs of a fan, opening along a stretch of coast some 2,000 kilometers long.<\/p>\n If this interpretation of the structure is correct, then it may preserve evidence of tectonic activity that preceded the breakup of Gondwana and clues about Antarctica’s eventual separation from Australia.<\/p>\n It may also help explain Antarctica’s other features, such as the towering Gamburtsev Subglacial Mountains and Transantarctic Mountains that border the EAFBP.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/06\/fan-shape2.jpg\")
A map of the EAFBP with a fan inset to show the similarity. (University of Genoa<\/a>)<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/06\/basin-province.jpg\")
A map of the EAFBP. (Armadillo et al., Nat. Geosci., 2026<\/a>)<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/06\/hand-analogy.jpg\")
A diagram illustrating how the EAFBP resembles a spread fan, or hand with too many fingers for some reason. (University of Genoa<\/a>)<\/p>\n![\"Subscribe](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/05\/FOMO-1200x628-_Dont-miss-the-next-breakthrough_-cosmic-colourful-642x336.jpg\")
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