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Beneath Antarctica’s Ice Is a Graveyard of Dead Continents (NYT)

1 December 2018


NYT title: Beneath Antarctica’s Ice Is a Graveyard of Dead Continents

NYT subtitle: Data from a European satellite has revealed the tectonic underworld below the frozen southernmost continent.

“The eastern section of Antarctica is buried beneath a thick ice sheet. Some scientists simply assumed that under that cold mass there was nothing more than a “frozen tectonic block,” a somewhat homogeneous mass that distinguished it from the mixed up geologies of other continents.

But with the help of data from a discontinued European satellite, scientists have now found that East Antarctica is in fact a graveyard of continental remnants. They have created stunning 3-D maps of the southernmost continent’s tectonic underworld and found that the ice has been concealing wreckage of an ancient supercontinent’s spectacular destruction.

The researchers, led by Jörg Ebbing, a geophysicist at Kiel University in Germany, reported their discovery earlier this month in Scientific Reports.

The findings relied on data from the Gravity Field and Steady-state Ocean Circulation Explorer (GOCE) satellite, which orbited Earth just 155 miles above the surface until late 2013, when it re-entered the atmosphere at the end of its mission. Called the “Ferrari of space,” this sleek instrument could measure the gravitational fields weaving through Earth’s crust and mantle.

Kate Winter, who studies Antarctica’s glaciers at Northumbria University in England and wasn’t involved in the study, said that the GOCE satellite data, “helped us to piece the supercontinent back together in magnificent detail.”

GOCE’s eye revealed that East Antarctica is a jigsaw puzzle of at least three geological titans named cratonic provinces. Cratons (from the Greek “kratos,” meaning “strength”) are stable rocky cores of continents that survived hundreds of millions of years of destructive action by Earth’s plate tectonics.

One craton has geological similarities with some of Australia’s bedrock, while another resembles part of India’s. The third is an amalgamation of pieces of old seafloors.

Fausto Ferraccioli, a senior geophysicist at the British Antarctic Survey and co-author of the study, said that “how and when all these provinces came together to make up East Antarctica as we see it today is still a matter of speculation and debate.”

The pieces may have been assembled as far back as 1 billion years ago, when the supercontinent Rodinia was built, or as recently as 500 million years ago, when another supercontinent, Gondwana, came together. Either way, what has been found beneath Antarctica is part of what’s left after Gondwana’s dissolution, around 160 million years ago.

Antarctica has been called the least understood continent on Earth, and many mysteries remain about its subsurface world. There’s only so much that magnetic and seismic data, and ground-penetrating radar attached to airplanes, can do to see through the 1.3-mile-thick ice sheet that covers 98 percent of it.

That’s where the European Space Agency’s GOCE (pronounced GO-chay) enters the story. Gravitational field strengths change depending on the objects they are associated with, and GOCE, with its ultrasensitive gravity-measuring probe and proximity to Earth’s surface, could detect masses deep below Antarctica’s icy surface in breathtaking detail.

“The beauty with GOCE is that we can go deep down in the lithosphere to get to the roots of the continents,” Dr. Ferraccioli said.

Dr. Winter said that despite these discoveries, the exact geological makeup of Antarctica’s innermost land, which sits in East Antarctica, “is yet to be discovered.” One solution would be to drill into the heart of the continent and sample the rock directly, using GOCE’s maps to guide scientists searching for the perfect spot to dig.

Knowing what rock the world’s largest ice sheet sits on is important in a warming world, as subglacial geology influences how ice shifts as the climate changes. But this study has more significant implications that go much deeper into our understanding of our world.

Plate tectonics is the engine that drives our planet. It forges volcanoes, fuels atmospheres, digs out ocean basins and creates mountain ranges. We can’t understand Earth’s entire evolution if we can’t complete the puzzle, and the data from the dead satellite has just helped discover a few more of its missing pieces.”



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