Inverse Grading Emerges From Particle‐Scale Migration Under Seasonal Freeze‐Thaw Forcing: Evidence From Multi‐Year Monitoring and Physical Modeling

Abstract Inverse grading, where coarse particles overlay finer materials, is common on talus slopes, yet its progressive formation under realistic conditions is rarely quantified. We integrate multi‐year field observations with controlled freeze‐thaw experiments to elucidate the processes driving particle migration that result in inverse grading and slope creep. Data from a talus slope in Northeast China show spatially varied downslope movements (2.0–19 mm/a), seasonal uplift during freezing, and net subsidence upon thawing. Laboratory models reveal systematic sorting: small particles move downward and downslope through expanded pores, while large particles shift and rotate with minimal descent. This vertical mobility contrast (small vs. large displaced by factors of 11–15) results in inverse grading over time. Depth‐dependent displacement shows differential deformation, with surface layers moving more than deeper layers. Our findings demonstrate that seasonal particle‐scale variations consistently drive talus restructuring, linking granular dynamics to landscape deformation and enhancing risk assessments in cold regions.