Human activities have substantially altered the transfer of surface material and sedimentary source-to-sink processes, particularly since the 1950s, thereby influencing global sediment flux. Surface erosion has profound effects on the Earth Critical Zone, wherein human activities significantly change erosion processes by intensifying both erosion flux and depth. While previous research has predominantly focused on erosion flux dynamics, variations in erosion depth remain poorly constrained due to the inherent limitations of conventional proxies (e.g., Sr-Nd isotopes, sedimentation rates), which typically fail to detect depth-related changes. The U-234/U-238 activity ratio, conventionally denoted as (U-234/U-238), can quantify sediment comminution age, which provides a qualitative indicator of changes in sediment sourcing or residence time. In this study, we utilize (U-234/U-238) derived from fine silicate fractions (<50 mu m) of Gonghai Lake sediments, located in the northeastern Chinese Loess Plateau, to reconstruct historical variations in erosion depth and assess anthropogenic impacts. Sr-Nd isotopic data confirm the local and upwind loess deposits as the primary sedimentary source, while uranium isotope records reveal multiple-stage comminution age shifts since the 1900s, reflecting human-driven erosion depth changes. Notably, mass sedimentation rates (sediment flux, indicative of erosion flux) exhibit relatively little variation in the last century, demonstrating an inconsistency between erosion flux and depth. This work establishes lacustrine sedimentary records of uranium isotopes as a novel proxy for quantifying source-area erosion depth and demonstrates that beyond affecting erosion flux, human activities profoundly influence erosion depth-an essential factor for designing effective soil system conservation strategies.