An international team of geoscientists identified a massive, fan-shaped geological structure beneath the East Antarctic Ice Sheet, according to research published June 3, 2026, in Nature Geoscience. The province, which spans roughly 30 interconnected subglacial basins, likely formed through rotational extension prior to the breakup of the Gondwana supercontinent.
Mapping the East Antarctic Fan-Shaped Basin Province
The newly identified East Antarctic Fan-Shaped Basin Province (EAFBP) covers a significant portion of the continent’s bedrock, an area that remains largely hidden under ice sheets reaching thousands of meters in thickness. Researchers, led by geophysicist Egidio Armadillo of the University of Genoa, utilized a synthesis of radar, seismic, gravity, and magnetic data to reconstruct the topography of the region, as reported by ScienceAlert.
The province is defined by a series of V-shaped basins that radiate from a common focal point near the South Pole. This “coherent continent-scale radial pattern” creates a geometry that widens toward the coast, resembling a handheld fan. The team formally proposed the name EAFBP to describe this physiographic unit, which encompasses well-known features including the Wilkes and Aurora basins, as well as the basin containing Lake Vostok, the largest known subglacial lake on Earth, according to Sci.News.
Tectonic Origins and Gondwana Breakup
The discovery suggests that the EAFBP formed through a process known as distributed rotational extension. In this tectonic model, the continental crust spread outward from a central pivot point, creating triangular gaps between blocks of crust. This structural formation bears a striking resemblance to a sphenochasm, a term defined in 1955 as “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.”
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Geoscientists believe this crustal stretching occurred before the supercontinent Gondwana fractured. By creating a zone of structural weakness, the EAFBP may have influenced the subsequent separation of Antarctica and Australia. As Nautilus reports, while these individual basins were studied previously, this research marks the first time they have been characterized as part of a single, unified megabasin system.
Implications for Antarctic Ice-Sheet Stability
Understanding the bedrock topography is critical for climate modeling because the ice sheet is not a static object; its movement is dictated by the basins and ridges beneath it. With the EAFBP underlying approximately 10 percent of Earth’s landmass and nearly half of the East Antarctic Ice Sheet, its influence on glacial flow is substantial.
“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.”
Egidio Armadillo et al., via Nature Geoscience
The researchers note that because the ice sheet sits on top of this complex basin network, the bedrock geometry directly controls the distribution of subglacial water and ice velocity. This makes the EAFBP a vital component in predicting how the southern ice cap will react to climate change. According to the Nature study, the discovery raises new questions regarding the precise timing of these tectonic phases and the geodynamic mechanisms that generated such a large-scale feature.
This follows our earlier report, Apolaki: The World’s Largest Underwater Volcanic Caldera Discovered.
Methodological Challenges in Subglacial Research
Investigating the Antarctic bedrock requires accounting for the immense mass of the ice sheet, which currently suppresses the continent’s elevation. If the ice were removed, the bedrock would rebound by as much as a kilometer. By combining reconstructed rebound topography with international compilations of radio-echo sounding data, the research team was able to resolve these large-scale features with unprecedented detail.
This approach highlights the evolution of Antarctic geophysical studies over the last several decades. Where early research relied on isolated observations, modern analysis integrates diverse datasets to reveal “continent-scale” surprises that have remained hidden for millions of years. The EAFBP now stands as one of the largest identified examples of rotational extension in continental crust, providing a new framework for understanding the geological history of the southernmost continent.
