Geomorphic processes at a snowpatch hollow on Gassan volcano, northern Japan

Present‐day geomorphic processes, in a snowpatch hollow on an andesitic volcano (Gassan, 1984 m ASL; 38° 38′ N, 140° 02′ E) where late‐lying snow survives nearly 10 months every year, have been measured for several years. Although soil temperature data show a concentration of freeze‐thaw activities in autumn, these fluctuations rarely drop to the effective temperature range for frost shattering. Wetting and drying rather than frost action is thought responsible for debris production which ranges from 2.12 to 49.68 g m−2 a−1, equivalent to a rock surface retreat of 0.001 to 0.019 mm a−1. Thawing of seasonal frost and saturation of soils induces frost creep and gelifluction: maximum values of surface velocity and depth of soil movement are 0.9 cm a−1 and 14 cm, respectively. Annually, slope lowering of 0.3 cm occurs in the pro‐nival and sub‐nival wash‐rill zones. In comparison with other snowpatch sites in the world, rates of soil movement and rock surface denudation are considerably lower at the study site, while fluvial action seems important. Copyright © 2002 John Wiley & Sons, Ltd.