Velocity of Sliding of an Ice-fall

Abstract

DURING the Nepal Himalaya P-29 (7,835m) Expedition of Osaka University Mountaineering Club, 1961, we had some experience on sliding and avalanches of an active ice-fall; analysing photographs taken by a Canon 2,000mm telephotographic lens from the base camp at 4,400 m high. Fig. 1 is a series of photographs taken at: (a) May 10, 1° 30′ p.m.; (b) May 11, 9° 30′ a.m.; (c) the same day 11° 30′ just after a small avalanche. By comparing the photographs (a) and (b) we can see that the glacier ice slid down as shown in Fig. 2. The distance of sliding on the original photograph was 2.0 mm. As the distance from the base camp to the ice-fall was 4 km, it corresponds to 4 m. As the estimated slope was 60°, the speed of sliding of the ice-fall became 6 m/day. Evidently this value is too large compared with the usual velocity of flow of a glacier. But as an avalanche occurred immediately afterwards, this value may not be unreasonable and gives some information on mobility of an ice-fall during the pre-avalanche period.