100km-wide “hidden giant” discovered beneath Antarctic ice sheet

Hidden Giant Under the Ice: Antarctic Discovery Reveals Clues to Future Sea Level Rise

For decades, pink granite boulders scattered across the volcanic peaks of the Hudson Mountains in West Antarctica have puzzled scientists. However, a study published in October 2025 may have finally solved the mystery surrounding their origin, linking the scattered boulders with a hidden, giant granite body – almost 100km across and nearly 7km thick – beneath Pine Island Glacier.

Unearthing Antarctica’s Jurassic Past

The discovery, led by researchers at the British Antarctic Survey (BAS), wasn’t just about identifying the source of the rocks. It was about dating them. Using U-Pb zircon geochronology, scientists determined the granite formed around 175 million years ago, during the Jurassic Period. This places the granite’s formation in a vastly different Antarctica – a temperate, ice-free landmass populated by conifers, ferns, and even dinosaurs like Cryolophosaurus and Glacialisaurus.

From Boulders to Buried Mass: How the Puzzle Was Solved

The age of the rocks was a starting point, but pinpointing their origin required a new approach. Airborne surveys conducted by BAS’ Twin Otter and other research aircraft revealed gravity anomalies beneath the Pine Island Glacier. These anomalies indicated a region of higher density, matching the expected signature of a large granite mass. By combining geological dating with gravity surveys, researchers were able to connect the surface boulders to their subterranean source.

“It’s remarkable that pink granite boulders spotted on the surface have led us to a hidden giant beneath the ice,” said Tom Jordan, lead author of the study and a geophysicist at BAS. “By combining geological dating with gravity surveys, we’ve not only solved a mystery about where these rocks came from, but also uncovered new information about how the ice sheet flowed in the past and how it might change in the future.”

Implications for Pine Island Glacier and Future Sea Level Rise

The discovery provides valuable insights into the past behavior of Pine Island Glacier, suggesting it once plucked rocks from the granite bedrock and deposited them across the Hudson Mountains when the ice sheet was thicker. This understanding is crucial because Pine Island Glacier is currently the fastest melting glacier in Antarctica, responsible for approximately 13% of the continent’s ice loss.

The underlying geology significantly influences how the glacier slides over the bedrock and how meltwater drains beneath it. The new findings will aid refine ice sheet computer models, improving predictions about how Antarctica will respond to future climate change and the potential impact on sea level rise.

Joanne Johnson, a co-author of the study and a geologist at BAS, emphasized the importance of rocks as historical records. “Rocks provide an amazing record of how our planet has changed over time, especially how ice has eroded and altered the landscape of Antarctica. Boulders like these are a treasure-trove of information about what lies deep beneath the ice sheet, far out of reach,” she said.

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Explore more about Antarctic research at the British Antarctic Survey.