Like a story from a science fiction thriller, Antarctica’s long buried history has been revealed using data from the dead European Space Agency’s gravity mapping satellite, unveiling the remnants of ancient lost continents hidden deep beneath the continent’s ice.
Scientists from Germany’s Kiel University and British Antarctic Survey (BAS) have used data from the European Space Agency (ESA), Gravity field and steady-state Ocean Circulation Explorer (GOCE) mission to unveil key geological features of Antarctica’s lithosphere – the rigid outer layer that includes the crust and the upper mantle.
The findings, published in Scientific Reports, reveal a prehistoric landscape littered with cratons—large, stable blocks of the Earth’s crust that are fossils of ancient continents. They are part of the lithosphere—which consists of the crust and upper mantle—and are generally found in the center of modern continental plates. Cratons form the oldest cores of the continents and hold key answers to unveil Earth’s early history.
“These gravity images are revolutionizing our ability to study the least understood continent on Earth—Antarctica,” said Fausto Ferraccioli, science leader of geology and Geophysics at the British Antarctic Survey. “In East Antarctica, we see an exciting mosaic of geological features that reveal fundamental similarities and differences between the crust beneath Antarctica and other continents it was joined to until 160 million years ago.”
“The new images show us the fundamental difference in the lithosphere beneath East and West Antarctica in agreement with previous seismic findings,” co-author Fausto Ferraccioli, of the British Antarctic Survey, told Newsweek. “We also found a greater degree of complexity in the interior of East Antarctica than is apparent from current seismic views, suggesting that this part of the continent is a mosaic of old cratons and orogens (regions where continents collide). Some of these regions have clear ties to formerly adjacent continents in the supercontinent Gondwana—such as Australia, India and Africa.”
“Antarctica is in many respects still a blank spot, and despite new seismological results, we did not expect to see that the ancient part of East Antarctica is so heterogeneous, ” said Jörg Ebbing, from Kiel University, in Germany, told Newsweek.
Dome-ridge features characterize Earth’s oceans while valley to bowl features prevail over continents. Several deep blue areas on the map reveal different cratons -some of the oldest cores of the continents, e.g. in Canada, Greenland, Africa and Antarctica.
GOCE measures differences in horizontal and vertical components of the gravity field – known as gradients. These gradients can be complex to interpret and so the authors combined these to produce simpler ‘curvature images’ that reveal large-scale tectonic features of the Earth more clearly.
“Our new satellite gravity gradient images improve our knowledge of Earth’s deep structure. The satellite gravity data can be combined with seismological data to produce more consistent images of the crust and upper mantle in 3D. This is crucial to understanding how plate tectonics and deep mantle dynamics interact”.
The contrast between the thinner crust and lithosphere of West Antarctica and the thicker crust and lithosphere of East Antarctica is apparent. The gravity image also suggests that East Antarctica is a mosaic of old cratons separated by younger orogens, similar to Australia and India. The pronounced blue area in West Antarctica may be related to the proposed Marie Byrd mantle plume, a feature of major interest for investigating the potential for high geothermal heat flux beneath parts of the West Antarctic Ice Sheet.
Dr Fausto Ferraccioli, Science Leader of Geology and Geophysics at the British Antarctic Survey and co-author of the study, said,
“Satellite gravity is revolutionizing our ability to study the lithosphere of the entire Earth, including its least understood continent, Antarctica. In East Antarctica, for example, we now begin to see a more complex mosaic of ancient lithosphere provinces. GOCE shows us fundamental similarities but also unexpected differences between its lithosphere and other continents, to which it was joined until 160 million years ago”.
The new study presents a view of the Earth’s continental crust and upper mantle not previously achievable using global seismic models alone. The authors noted that, despite their similar seismic characteristics, there are contrasts in the gravity signatures for ancient parts of the lithosphere (cratons), indicating differences in their deep structure and composition. These features are important. Because they form the oldest cores of the lithosphere, they hold key records of Earth’s early history.
The Daily Galaxy via British Antarctic Survey and Newsweek
Image credit: map of Gondwana with thanks to Merrigum.com