Mysterious Pink Rocks found in Antarctica

 A massive structure hidden under the Antarctica’s ice for 175 million years

Antarctica looks like a clean white ice sheet from far away, but the important action happens deep down under the surface. There, the ice meets rock, water, and sediments. That contact zone controls how fast a glacier moves and how easily it can change speed. Scientists uncovered a big secret that Antarctica has been hiding, a giant granite deposit buried beneath the Pine Island Glacier. Ancient granite boulders reveal a vast hidden structure beneath Pine Island Glacier, reshaping understanding of Antarctic ice flow. Pink granite boulders scattered across the dark volcanic peaks of the Hudson Mountains in West Antarctica have pointed scientists to a massive granite formation hidden beneath Pine Island Glacier. This buried body spans nearly 100 km's (about 62 miles) in width and reaches approximately 7 km's (around 4.3 miles) in thickness, making it roughly half the size of Wales in the UK. What began as a mystery involving a few strange pink boulders turned into a major geological revelation. The discovery not only answers old questions but also changes how we see the frozen continent’s past and its future.

In the Hudson Mountains, pink granite boulders sit scattered among dark volcanic rocks. Their color stands out like a clue left behind. For decades, no one knew how these boulders ended up there. A team from the British Antarctic Survey (BAS) decided to find out. By measuring radioactive decay inside tiny mineral crystals, the scientists discovered that the granites formed around 175 million years ago. That explained their age but not their location. The boulders didn’t belong on those mountains. Something had moved them, something massive. For decades, the presence of these distinctive boulders high in the mountains has raised questions. Researchers have long wondered how the rocks arrived there and what they might reveal about the history and future behavior of the Antarctic ice sheet. A research team led by the British Antarctic Survey (BAS) analyzed the granites by measuring the radioactive decay of elements trapped within microscopic crystals. Their results showed that the rocks formed around 175 million years ago. Even so, the process that carried these boulders to their current locations remained unclear until scientists gathered new data from the air. Dr. Joanne Johnson, a geologist at BAS and co-author of the study, helped collect the boulders during fieldwork in the Hudson Mountains. “Rocks provide an amazing record of how our planet has changed over time, especially how ice has eroded and altered the landscape of Antarctica,” she said. “Boulders like these are a treasure trove of information about what lies deep beneath the ice sheet, far out of reach.”

High resolution gravity measurements collected by the BAS’s Twin Otter and other aircraft flying over the region detected an unusual signal beneath the glacier. This signal closely matched what scientists would expect from a large granite body buried deep below the ice. “By identifying their source, we have been able to piece together how how they got to where they are today, giving us clues about how the West Antarctic Ice Sheet may change in future, information that is vital for determining the impact of sea level rise on coastal populations around the world.” Thousands of years ago, during the last ice age, the Pine Island Glacier was thicker and far more powerful than it is today. It tore rocks from the granite bed below, moved them across the landscape, and dropped them on the Hudson Mountains as the ice thinned. Each boulder now marks where the glacier once stood. These clues help scientists rebuild the glacier’s history. They feed this data into computer models that predict how the ice might move in the future. Accurate models matter because Pine Island Glacier is one of Antarctica’s fastest-melting regions. What happens there affects sea levels worldwide. Connecting the surface boulders to this concealed granite mass has provided a major advance. It resolves a long-standing geological puzzle and offers important insight into how Pine Island Glacier behaved in the past, when a much thicker ice sheet was capable of tearing rocks from the bed and depositing them high in the surrounding mountains.

Reconstructing ice thickness and flow patterns during the last ice age (around 20 thousand years ago) allows researchers to improve ice sheet computer models, which are essential for forecasting how Antarctica may respond to ongoing climate change. The buried granite doesn’t just belong to the past, it shapes the present too. The type of rock under a glacier determines how the ice moves and melts. Granite can create friction that slows the sliding ice, while melt water channels beneath it can make the ice flow faster. Understanding this hidden foundation helps scientists explain why Pine Island Glacier is losing ice so rapidly. This discovery also improves models that simulate future sea level rise. Each new piece of data makes predictions more reliable and gives coastal communities a clearer picture of what’s coming. The answer came from top of the area. Aircraft equipped with gravity sensors flew over Pine Island Glacier and detected a strange signal beneath the ice. The data revealed a hidden granite deposit almost 100 km's (62 miles) wide and 7 km's (4.3 miles) thick, about half the size of Wales. It lay buried deep beneath the glacier, unseen for millions of years. “It’s remarkable that pink granite boulders spotted on the surface have led us to a hidden giant beneath the ice,” said Dr. Tom Jordan, lead author and 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.” Those words capture the excitement of the find. The boulders weren’t random. They were fragments from this underground giant, carried to the mountains by ancient ice.

The discovery also sheds light on present-day processes. Beneath Pine Island Glacier, a region that has seen some of the fastest ice loss in Antarctica in the last few decades, the geology strongly influences how ice slides over the bed. The new findings will help improve computer models of ice flow that are used to project sea level rise. Pine Island Glacier sits in a region where small changes can trigger large responses. Ice flow depends on the slope of the bed, the roughness of the rock, the presence of water, and the type of sediment the ice grinds up. Knowing whether the bed includes a large granitic block helps scientists narrow down those conditions. This study shows how researchers find ways to conduct field work in places they cannot directly reach. They combined the physical samples that ice leaves behind with wide-area geophysical measurements. Together, those tools improve the “under-the-ice map” that scientists rely on when they try to explain past glacier behavior and estimate what might come next.

Dr. Joanne Johnson collected the rocks during fieldwork around the Hudson Mountains as part of the International Thwaites Glacier Collaboration. She says, “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. By identifying their source, we have been able to piece together how they got to where they are today, giving us clues about how the West Antarctic Ice Sheet may change in future, information that is vital for determining the impact of sea level rise on coastal populations around the world.” Geology revealed the rocks’ origin, while geophysics uncovered the structure hidden below, turning a small mystery into a major discovery. The pink granite boulders are more than chunks of stone on a frozen mountain. They connect Earth’s fiery beginnings to its icy present. This study highlights how combining different strands of science, in this case, geology and geophysics, can provide new insights into the hidden processes shaping our planet.