Beneath the rocky surface of Mount Timpanogos in Utah, a hidden world of ice has been quietly enduring for thousands of years, unknown to those who walked above it. University of Utah researchers, using gravity-sensing instruments to peer beneath the rubble, have mapped a buried glacier that is 83% ice — a discovery that reframes how humanity understands the water stored within its mountains. Extrapolated globally, some 50,000 such rock glaciers may collectively hold 48 gigatons of freshwater, a reservoir of consequence in an era when the reliability of water is no longer assumed.