Beneath East Antarctica’s undulating ice sheet lies an ancient, river-carved landscape that gives an ideal snapshot of the region before glaciers covered the continent, a brand new study finds.
Although many of the land buried under the ice sheet was eroded over the eons by moving masses of ice, satellite data show that a patch adjoining to the Aurora and Schmidt subglacial basins has remained largely unscathed for as much as 34 million years.
“We could see that there was something just like the ghost of the landscape under the ice,” study co-lead creator Stewart Jamieson, a professor of geography on the University of Durham within the U.K., told Live Science. “Sooner or later up to now, there’s been rivers flowing over it, which robotically must mean that it’s from before the ice sheet grew.”
Jamieson and his colleagues used preexisting data to map bumps and troughs on the ice surface mirroring changes in elevation within the underlying landscape. These slight gradients revealed a “little island of topography” buried 1.2 miles (2 kilometers) below the surface and three “blocks” of land separated by U-shaped valleys, Jamieson said.
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The blocks likely formed a continuous landmass, he said. But when the traditional supercontinent Gondwana, which included Antarctica, broke up throughout the Cretaceous period (145 million to 66 million years ago), tectonic forces can have ripped them apart. “As a part of that pulling away of continents, it’s probably stretched our landscape and broken it up into those three blocks,” Jamieson said.
When the climate cooled following the Cretaceous, ice caps can have formed on top of every block and carved out valleys because the ice melted and water trickled down from the peaks. “Those rivers were probably flowing towards the coast, which is a couple of hundred kilometers away, at a time when that coast was opening up,” Jamieson said.
The massive ice sheet that also covers Antarctica today grew around 34 million years ago and smothered your entire continent, in keeping with the study, published Tuesday (Oct. 24) within the journal Nature Communications.
“Suddenly, that landscape is frozen in time,” Jamieson said.
But not all of East Antarctica was preserved beneath a frigid blanket. In places where the ice grew thickest, the load that piled onto the land caused melting at the bottom of the ice sheet, giving rise to a skinny layer of water. This allowed the ice to grind over the land and erode it over tens of millions of years.
Within the newly discovered location, the ice didn’t grow thick enough to create a layer of water, Jamieson said. “If you take a look at the pattern of ice flow within the region, it’s form of going faster on either side of our landscape. But then on top of our landscape it’s going really slowly, and that is since it’s mainly frozen to its bed,” he said.
Whether this landscape has stayed completely the identical for 34 million years is somewhat opaque. Periods of warming that deglaciated parts of East Antarctica until about 14 million years ago can have caused a number of the ice above it to melt, Jamieson said.
“What could be really intriguing is definitely going to that location and drilling through the ice to get a sample of the rock and sediment underneath,” he said. “That will be the one way we could confirm the age.”
Ultimately, understanding what lies beneath the East Antarctic ice sheet will help researchers predict its fluctuations in a warming world. “We’d like to grasp the form of the landscape in order that we are able to understand why the ice is flowing the way in which it does now and the way it’d react in the long run,” Jamieson said.