Pink Granite Boulders Reveal Vast Hidden Structure in West Antarctica

Scientists in West Antarctica have found a large granite structure buried under the ice after studying pink boulders scattered across the Hudson Mountains. The rocks, which do not match the local dark volcanic stone, came from this hidden mass about 100 kilometers wide and 7 kilometers thick, roughly half the size of Wales. The team traced the boulders to their source under the Pine Island Glacier using field work, satellite images, and gravity surveys. This find dates back to the Jurassic period, around 175 million years ago, and sheds light on how the ice sheet has changed over time.

Background

For decades, researchers have noticed these pink granite boulders high up in the Hudson Mountains. The rocks stood out against the dark volcanic peaks around them. No one could explain where they came from because the area's geology is mostly volcanic, not granite. The boulders sat there, puzzling scientists who visited the site.

Teams from the British Antarctic Survey took samples during field trips near the Hudson Mountains. They worked as part of larger projects, like the International Thwaites Glacier Collaboration. These efforts aim to understand the West Antarctic Ice Sheet, which holds enough ice to raise global sea levels by several meters if it melts.

The pink granite is tough and resists erosion. Glaciers carried these boulders from deep under the ice and dropped them on the mountainsides during past ice ages. When the ice was thicker, about 20,000 years ago, it plucked rocks from the bedrock and moved them uphill. Finding the source of these rocks solves a long mystery and opens a window into Antarctica's hidden past.

Key Details

The breakthrough came from combining several methods. First, scientists dated the rocks using radioactive decay in tiny crystals inside them. This showed the granite formed 175 million years ago in the Jurassic period.

How They Mapped the Hidden Structure

Next, they flew aircraft over the area with special tools to measure gravity. The Twin Otter plane from the British Antarctic Survey picked up signals from beneath the Pine Island Glacier. These matched what you would expect from a large granite body. Granite has a different density than the surrounding rocks, so it creates a clear gravity signature.

The structure sits under the glacier, which has lost ice quickly in recent decades. Field visits confirmed the boulders' makeup. Mineral analysis and 3D models linked the surface rocks directly to the buried mass. The granite influenced how ice flowed, shaped mountains, and affected erosion patterns over millions of years.

"It's remarkable that pink granite boulders spotted on the surface have led us to a hidden giant beneath the ice. 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." – Dr. Tom Jordan, geophysicist at British Antarctic Survey

Dr. Joanne Johnson, a geologist who collected the rocks, pointed out how such finds reveal deep history. The team published their work in the journal Communications Earth & Environment.

What This Means

This discovery changes how we understand the West Antarctic Ice Sheet. The granite bedrock affects how ice slides over the ground and how water drains underneath. In places like Pine Island Glacier, fast ice loss has raised worries about sea level rise. Better knowledge of the bedrock helps refine computer models that predict future melting.

In the past, thicker ice interacted with this granite, carving the landscape we see today. Models now account for these old flow patterns, making forecasts more accurate. This matters for coastal areas worldwide, where rising seas could flood homes and cities.

The find shows how small clues on the surface can reveal big secrets below. Scientists used geology, geophysics, and fieldwork together to piece it together. It highlights Antarctica's role in global climate and the need to keep studying its ice and rocks.

Researchers plan more surveys to map other hidden features. Understanding bedrock helps track ice stability. As the climate warms, these details guide efforts to predict changes and protect communities from rising oceans. The pink boulders, once a puzzle, now anchor a clearer picture of Antarctica's geology and its future.