Arctic soil patterns analogous to fluid instabilities.

Slow-moving arctic soils commonly organize into striking large-scale spatial patterns called solifluction terraces and lobes. Although these features impact hillslope stability, carbon storage and release, and landscape response to climate change, no mechanistic explanation exists for their formation. Everyday fluids-such as paint dripping down walls-produce markedly similar fingering patterns resulting from competition between viscous and cohesive forces. Here we use a scaling analysis to show that soil cohesion and hydrostatic effects can lead to similar large-scale patterns in arctic soils. A large dataset of high-resolution solifluction lobe spacing and morphology across Norway supports theoretical predictions and indicates a newly observed climatic control on solifluction dynamics and patterns. Our findings provide a quantitative explanation of a common pattern on Earth and other planets, illuminating the importance of cohesive forces in landscape dynamics. These patterns operate at length and time scales previously unrecognized, with implications toward understanding fluid-solid dynamics in particulate systems with complex rheology.