Gravity Map Reveals Tectonic Secrets Beneath Antartica’s Ice
Satellite data shows East and West Antarctica have very different geologic histories
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Geologists have done pretty well piecing together the history of plate tectonics, or how sections of Earth’s crust have pinballed across the globe crashing into one another and pulling apart. But there’s one big puzzle piece they still need to figure out: Antarctica. That’s because the continent is covered with a layer of ice averaging over a mile thick, meaning studying the bedrock directly is nearly impossible. But recently, a satellite measuring the pull of Earth’s gravity was able to penetrate that ice, reports Hannah Osborne at Newsweek, revealing the tectonic history locked below the frozen continent.
The data came from the European Space Agency’s GOCE (Gravity and Ocean Circulation Explorer) a satellite that orbited the earth between 2009 and 2013. During its mission, the craft collected precise measurements of Earth’s gravity, which reveal the thickness and density of the planet’s lithosphere, a combo of the crust and upper mantle. During the last year of its mission, as it was running out of fuel, operators dropped the satellite to just 158 miles above the ground to get even better readings before GOCE burned up.
Ever since, researchers have been converting that data into super-accurate 3D maps of the lithosphere. An exciting finding, published in the journal Scientific Reports, is that the crusts from eastern and western Antarctica are very different, suggesting the two halves of the continent have diverging histories.
“These gravity images are revolutionizing our ability to study the least understood continent on Earth, Antarctica,” geophysicist Fausto Ferraccioli of the British Antarctic Survey and co-author of the paper says in a statement.
In particular, the data shows that the crust in West Antarctica is thinner than East Antarctica, which is made up of a patchwork of old cratons, or the stable chunks of crust that make up the nucleus’s of continents, held together by younger orogens, or mountain belts. The more complex east appears to be firmly linked to the the breakup of the supercontinent Gondwanaland 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,” Ferraccioli tells Osborne. “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. Some of these regions have clear ties to formerly adjacent continents in the supercontinent Gondwana—such as Australia, India and Africa."
The new maps will help researchers figure out just how the ancient bits and pieces of continents fit together and shifted over time. But the maps have more than historic interest. Knowing what lies beneath the ice sheet will help scientists understand its behavior and how the bedrock will respond as climate change begins melting the ice, causing the rock to rebound upward.
The gravity map is not the only recent study revealing the geology of the frozen south. Another map put together by the British Antarctic Survey and its collaborators in July combined 50 years of magnetic anomaly data collected across the continent. That data helps researchers create detailed maps of subglacial mountain ranges and other features trapped below the ice sheet. Combined, these and other studies are beginning to give us our first real view of a continent hidden in plain sight.