Drainage state, glacial dynamics and kinds of ice at the terminus of Lys Glacier (Western Alps)

Abstract

The Lys glacier is formed of superposed layers several meters thick. Most of the layers consist of granoblastic ice with centimetric crystals and little inner moraine, except at their boundary, where this increases sharply and the crystals are small with evident glaciotectonic structures. At the terminus, this pile of layers rests on an isoclinally folded stratum of ice-rich sand. Below this bed, there is granoblastic ice, which also constitutes the substrate of the depositional end moraines formed during 1980–86: it thus seems likely that it is now acting as the inert substrate of the actively moving ice, separated from it by the stratum of ice-rich sand, which would seem to represent their lodgment till. This structure is not common on the Italian side of the Alps. The peculiarity of the Lys can probably be attributed to its cyclical tendency to display rapid advances, very similar to "micro-surge" episodes, in years with high summer temperatures.