Ice Planet Recon: Giant Fan-shaped Geological Structure Discovered Beneath East Antarctica
Editor’s note: there are currently two advanced missions heading for the jovian system – Europa Clipper and ESA Juice – to study icy Europa and the other icy worlds orbiting Jupiter. How we observe these ice worlds and formulate an idea of their internal structure – including possible subsurface oceans – possibly habitable – will be based upon lessons learned on our home world – which is also an ice world.
Enormous subglacial basins
An international team of researchers including our Department of Geography has discovered a vast geological structure hidden beneath the East Antarctic Ice Sheet. The structure is made up of a system of enormous subglacial basins buried in ice over three kilometres thick in parts.
Together, the basins form a giant fan-shaped structure on a continental scale. The team have named it the East Antarctic Fan-shaped Basin Province.
It includes some of Antarctica’s best-known subglacial features, such as the Wilkes and Aurora basins and the basin hosting Lake Vostok, the largest known subglacial lake on Earth.
Although these basins have been individually studied in the past, this is the first time their connection as part of a single coherent structure has been recognised.
Distributed rotational extension
Analysis suggests the structure was formed by a process known as distributed rotational extension.
This is where the continental crust has spread out from a central point. The pattern is similar to a hand, with the base of the thumb as the fixed point, and fingers spreading out showing the stretching. The gaps between the fingers are like the triangular basins that form as it opens.
Understanding Antarctica’s geological history
The East Antarctic Fan-shaped Basin Province could be one of the largest examples of rotational extension ever seen in continental crust.
It may have developed through multiple tectonic phases linked to the evolution of the Gondwana supercontinent and the later separation between Antarctica and Australia and could even have influenced this break-up.
The discovery also raises fresh questions – particularly around the precise age of the structure and the geodynamic mechanisms that generated it.
However, the significance of the discovery extends beyond historical insight.
The shape of the bedrock hidden beneath the ice sheet continues to influence ice flow today, controlling the distribution of subglacial basins and lakes. This could potentially affect the stability of parts of the Antarctic Ice Sheet that are particularly sensitive to climate change.
Rebounded topography
To investigate the structure, researchers combined subglacial topography with geological observations, gravity, magnetic and seismic data, and crustal and lithospheric models.
They found that the observed structure is a result of a deep tectonic process within the Antarctic lithosphere.
Dr Guy Paxman from our Department of Geography was part of the research team.
He led on calculating what the elevation of the land surface of East Antarctica would be if all the ice were removed (which would cause the land to rebound upwards by as much as one kilometre).
This ‘rebounded topography’ was used in analysis of the orientation and elevation of the topography of the newly discovered structure.
A fan-shaped subglacial basin province in East Antarctica formed by rotational extension, Nature Geoscience (open access)
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