In the Arctic, rivers are rewriting the rules of erosion science — carving through thawing permafrost in ways that centuries of geomorphological understanding never anticipated. As polar temperatures rise faster than anywhere else on Earth, the frozen ground that once held riverbanks firm for millennia is collapsing, creating feedback loops that outpace every model built on stable landscapes. What is unfolding in these remote waterways is not merely a regional anomaly, but a signal that the foundational assumptions of Earth science may need to be reconsidered in the age of accelerating climate