ABSTRACT
If a glacier has been moving over an area for a very long time, erosion will probably have removed much of the sediment and weathered debris which may have been present in the past. The debris content of ice adjacent to a glacier bed may be as much as 30 per cent by volume. The Glen flow law at any part of a glacier therefore must be a function of location, defined by the local crystallographic fabric and stress situation. Ice passing round the sides of upstanding parts of a glacier bed, or round other obstacles such as boulders, is subject to transverse compression and longitudinal extension. Pressure fluctuations at glacier beds change ice melting-point, and water may be squeezed out of the ice by high pressure. The water tends to flow towards zones of lower pressure, such as cavities at the bed.
