The structure, named the East Antarctic Fan-shaped Basin Province, lies under ice more than three kilometres thick in places. It brings together features long studied separately, including the Wilkes Basin, Aurora Basin and the basin containing Lake Vostok, the largest known subglacial lake on Earth. The discovery changes the way researchers understand a broad sector of East Antarctica, shifting it from a collection of isolated buried depressions to a single continent-scale geological framework.
The finding is based on a joint interpretation of sub-ice topography, gravity measurements, magnetic data, seismic information and models of the crust and lithosphere. Researchers concluded that the basins radiate from a focal area near the South Pole, forming a pattern similar to an opening fan. The alignment suggests the structure was shaped by rotational extension, a process in which continental crust stretches outward from a relatively fixed point.
The scale of the hidden province is significant because East Antarctica has often been viewed as the more stable part of the Antarctic system, compared with the faster-changing West Antarctic Ice Sheet. The newly mapped basin network underlies a large part of the East Antarctic Ice Sheet, making it relevant not only to geological history but also to present-day ice dynamics. Bedrock shape controls how ice flows, where water collects beneath the ice and how glaciers discharge towards the coast.
The province may be one of the largest examples of rotational extension identified within continental crust. Its formation is thought to be linked to tectonic episodes associated with the ancient supercontinent Gondwana and the later separation of Antarctica and Australia. The pattern may also help explain the uplift of the Gamburtsev Mountains, the structure of parts of the Transantarctic Mountains and the curved shape of the Antarctic-Australian continental margin.
The study’s authors say the timing of the tectonic activity remains unresolved. The deformation may have taken place in more than one phase, and the geodynamic forces behind it are still being tested. Antarctica’s bedrock remains among the least directly observed geological regions on Earth because more than 99 per cent of the continent is covered by ice, limiting direct field access and requiring scientists to rely heavily on airborne radar, satellite data and geophysical modelling.
The discovery comes as polar researchers are building a sharper picture of Antarctica’s hidden landscape. Earlier mapping efforts identified mountains, valleys, canyons, lakes and plains beneath the ice sheet, including thousands of small landforms that had not been resolved in older maps. These advances are improving ice-sheet models by giving scientists a more accurate view of the bed over which ice moves.
Subglacial basins are especially important because they can steer ice flow and affect the formation of lakes and water systems beneath the ice. Water at the base of an ice sheet can lubricate movement, alter friction and influence the pace at which glaciers drain into the ocean. Sedimentary basins may also store or release groundwater, a factor increasingly seen as relevant to long-term ice behaviour.
East Antarctica contains enough ice to raise global sea levels by many metres if destabilised over long timescales, though such changes would unfold unevenly and depend on ocean warming, atmospheric conditions, ice-shelf stability and bedrock geometry. Scientists are particularly interested in basins that slope inland below sea level, as these can make ice more vulnerable to retreat once warm ocean water reaches grounding zones.
The new fan-shaped province does not mean immediate instability across East Antarctica. Instead, it provides a broader structural explanation for why some basins, troughs and subglacial lakes are positioned where they are. That framework can help refine projections of ice-sheet response under different climate scenarios, especially in sectors where existing models still carry substantial uncertainty.
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