At the edge of East Antarctica, a glacier the width of Manhattan has been moving two metres every day for as long as instruments have measured it — not as a slow grind, but as a high-velocity conveyor draining a catchment larger than California into the Ross Sea. Byrd Glacier is not yet in crisis, but it exists within a system whose balance depends on the continued integrity of the Ross Ice Shelf, a buttress that, if lost, would remove the brake on outlets capable of measurably lifting oceans worldwide. The deeper story here is not of a glacier accelerating today, but of ancient geometry and m