A giant fan-shaped structure has been found under the Antarctic ice

Some of these depressions have been known before. Among them are the Wilkes and Aurora basins, and the area where Lake Vostok, Earth's largest known subglacial lake, is located. But now scientists have shown that all these elements may be parts of one big system. It's called the East Antarctic fan-shaped depression province.

The discovery is not only important for geology. The shape of the bed beneath a glacier affects the way the ice moves. Which means this hidden structure could be important for understanding the future of the Antarctic ice sheet.

Details

East Antarctica is covered by a huge ice sheet. In some places, the ice is more than 3 kilometres thick. That's why it's impossible to see the topography beneath it directly: scientists study it using data on subglacial floor height, gravity, magnetic field, seismics and models of the Earth's crust.

The new work is published in Nature Geoscience.

The authors combined different types of data and saw that under East Antarctica there is not a set of individual troughs, but a large connected structure. It diverges in a fan on a continental scale.

The easiest way to visualise it is as a palm. There is a point from which the "fingers" diverge in different directions. Between them there are gaps - similar to triangular basins. Approximately such a pattern, according to researchers, once appeared in the Earth's crust of Antarctica.

Scientists believe that the structure could have appeared due to the stretching of the Earth's crust. Millions of years ago, the continental crust in this area deformed and as if "opened" around the central area. Such a process is called distributed rotational stretching. For the reader, it's simpler: part of the ancient Earth's crust slowly stretched and rotated, causing large depressions to form.

This story may be related to the ancient supercontinent Gondwana and the later separation of Antarctica and Australia. That is, the structure found may be a trace of very old tectonic processes that occurred long before the modern ice sheet.

Why it's important

At first glance, it seems that the shape of the rocky floor beneath the ice is just geology. But for Antarctica, it's also a matter of ice.

Ice doesn't lie still. It flows slowly from the centre of the continent to the edges, like a very thick mass. If there are deep depressions, ridges, lakes and bumps underneath, they can direct the movement of the ice, speeding it up or slowing it down.

That's why the new structure is important for climate models. To understand how an ice sheet might respond to warming, we need to know what lies beneath it. The subglacial topography affects where the ice is more stable and where it is more sensitive to change.

Backcountry

Antarctica appears to be a flat white desert, but beneath the ice lies the real continent: mountains, valleys, hollows, lakes and ancient faults. Many of these objects cannot be seen with the eyes, so they are found by indirect evidence - like doctors see internal organs on scans.

Lake Vostok is one of the most famous of these objects. It is under kilometres of ice and has long been studied as an example of an isolated subglacial environment. Now it turns out that the Lake Vostok basin may be part of a much larger fan-shaped system beneath East Antarctica.

The new study also shows that Antarctica is important not only as an icy continent, but also as an archive of ancient geological history. Beneath its ice, traces of processes that are linked to the breakup of ancient continents and the formation of the modern map of the Earth are preserved.

Source

Study: Egidio Armadillo et al, "A fan-shaped subglacial basin province in East Antarctica formed by rotational extension", Nature Geoscience, 2026.