Bright pink granite stones scattered across the dark volcanic peaks of the Hudson Mountains in Antarctica have led scientists to a remarkable discovery.
Researchers believe a large mass of granite, nearly 100 km wide and 7 km thick – roughly half the size of Wales – lies buried beneath the Pine Island Glacier. These unusual rocks have puzzled researchers for decades.
Located high on the mountain ridges, the rocks seemed out of place, prompting questions about their origin and what they might reveal about Antarctica’s past and future.
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Rock Age
According to a report in Science Daily, a research team led by the British Antarctic Survey (BAS) analyzed the granite by examining the radioactive decay of elements trapped within small mineral crystals. This technique indicated the rocks formed approximately 175 million years ago, during the Jurassic period.
While the age of the rocks has been determined, their journey to the mountain peaks remained unclear until scientists gathered new data from aerial surveys of the region.
Hidden Structure
Using highly sensitive gravity measurements collected by BAS’s Twin Otter aircraft and others, researchers detected an unusual signal beneath the glacier. The data aligned with what scientists would expect from a large granite body hidden under the ice.
Connecting the rock fragments on the surface to this deep underground formation solved a long-standing mystery.
The discovery also reveals that the Pine Island Glacier once flowed in a very different way, pulling rocks from its base and carrying them uphill when the ice sheet was much thicker. Understanding glacial behavior is crucial for predicting future ice sheet responses to climate change.
This finding provides vital insights into how glaciers behaved during the last ice age (around 20,000 years ago). By understanding past ice thickness and flow patterns, scientists can improve computer models used to predict how Antarctic ice sheets may respond to future climate change.
Dr. Tom Jordan, the lead author and a geophysicist at BAS, analyzed the aerial data.
“It’s remarkable that the pink granite boulders visible at the surface have led us to a hidden giant beneath the ice. By combining geological dating with gravity surveys, we’ve not only solved the mystery of the origin of these rocks, but also uncovered new information about how the ice sheet flowed in the past and how it might change in the future,” he said.
The findings also highlight how the geology beneath the Pine Island Glacier influences current conditions. This region has experienced some of the fastest ice loss in Antarctica over the past few decades.
The type of rock underneath affects how easily the ice slides and how meltwater moves beneath it.
A better understanding of these processes will help refine models that predict future sea level rise.
Antarctica’s History
Dr. Joanne Johnson, a co-author and geologist at BAS, collected the rock fragments during fieldwork in the Hudson Mountains as part of the International Thwaites Glacier Collaboration.
“The rocks provide an extraordinary record of how our planet has changed over time, particularly how ice has eroded and reshaped the Antarctic landscape. Boulders like these are treasure troves of information about what lies far beneath the ice sheet, beyond the reach of conventional exploration,” Johnson said.
“By identifying their source, One can piece together how they came to be where they are now, giving us clues about how the West Antarctic Ice Sheet may change in the future – information that is vital for determining the impact of sea level rise on coastal populations worldwide,” she added.
The research demonstrates how combining geology and geophysics can reveal hidden features beneath Antarctica and deepen our understanding of the forces shaping the planet.
