TV-VIDEO OBSERVATIONS OF BED AND BASAL SLIDING ON STORGLACIAREN, SWEDEN

Four boreholes in Storglaciaren, a small-valley glacier in northern Sw eden, were inspected with a video camera. In two of the boreholes, the apparent glacier bed was filmed. In one borehole, the bed was found t o be composed of soft sediment, but in the other it consisted of bedro ck. In the latter, the camera moved 5.6 mm relative to the bed during an 80 min period. The recorded camera movement showed a background mot ion which is in the expected range of basal sliding. Superimposed on t he background motion, a jerky motion of a high-speed spike was found. The jerky motion is interpreted as a stress release induced by local t opography at the ice-bed interface.