ABSTRACT
Geomorphology The similarity between karst and glacier discrete drainage systems results in corresponding morphological similarities: allogenic streams, blind valleys, stream sinks, vadose shafts, phreatic conduits, and pocket valleys (spring heads, réculées) are all present. In glacier caves, phreatic conduits are elliptical in section, vadose canyons meander, and vertical shafts are fluted and may widen at the base. At the glacier bed,
channels may be carved up into the ice and down into till or bedrock. Channels cut up into ice are termed Röthlisberger channels; they are transient as they migrate with the ice, and can be annihilated by creep closure or being dragged over a bedrock obstacle. In contrast, channels cut into bedrock remain fixed in position, and may persist over winter. They are termed Nye channels, and where they exist may promote the rapid establishment of drainage systems. Subglacial streams flowing on unconsolidated materials like till also form channels. Their behaviour is poorly understood, but they may persist, providing they do not become choked on their own sediment.
