The unusual boulders, perched high in the mountains, have puzzled scientists for decades. Where did they come from, and what could they reveal about the ice sheet's past and future?

A team of researchers, led by British Antarctic Survey (BAS), dated the granites using the radioactive decay of elements locked within microscopic crystals, discovering that the rocks formed around 175 million years ago, during the Jurassic period. But how the boulders came to rest in these mountains remained mysterious until new evidence came from airborne surveys. The study is published in the journal Communications Earth & Environment.

Precise gravity measurements collected by the BAS' Twin Otter and other aircraft flying over the region revealed an unusual geological signal from beneath the glacier, matching the signature expected from a buried granite.

Linking the scattered boulders with this hidden giant granite has provided a breakthrough. It not only solves a long-standing geological puzzle but also offers vital clues to how Pine Island Glacier behaved in the past, plucking rocks from the bed and depositing them on the mountains at a time when the ice sheet was much thicker. Understanding the ice thickness and flow regimes during the last ice age (around 20 thousand years ago) helps scientists refine ice sheet computer models, which are critical for predicting how Antarctica will respond to future climate change.