Arctic Soil Patterns as Large, Exceedingly Slow Fluid Instabilities*

Slow-moving arctic soils commonly organize into striking large-scale spatial patterns called solifluction terraces and lobes. While these features are viewed as hallmarks of freeze-thaw processes, 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. We use a scaling analysis to show that soil cohesion and hydrostatic effects alone can lead to similar large-scale patterns in arctic soils. A rich dataset of high-resolution solifluction lobe spacing and morphology across Norway supports theoretical predictions. Our findings provide a quantitative explanation of a common pattern on Earth and Mars, 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. Yet fundamental questions remain. If solifluction patterns are analogous to classic fluid instabilities, then why do we only see them in cold places on Earth? Annual temperature data from Norway point toward a broad climate control on solifluction lobe morphology. What are the necessary and sufficient ingredients to initiate solifluction instabilities, and how will these conditions control landscape response to climate change? To get at these questions, we are using a combination of theory, satellite imagery analysis, fieldwork, and physical experiments in a walk-in climate chamber.