Observations on a Surging Glacier in East Greenland

Abstract Recent observations on Bjornbo Gletscher (lat. 71°., long. 25° W.), East Greenland, have revealed that it has several features characteristic of a surging glacier. One outstanding feature is the occurrence of drop-like ice masses in the lower part of the glacier which do not appear to belong to the main glacier. A detailed petrographic comparison between the morainic debris surrounding these drop-like ice masses and the rocks occurring in the upper part of the glacier has been made. The results indicate that these drop-like ice masses have been inserted into the main glacier. This drop-like form is explained as being due to ice transport from the side valleys, and this occurred over a short period of time during the movement (or surge) of the main glacier. Because of the highly variable rock types occurring in the respective accumulation zones, petrographic examinations of other moraines in the ablation zone have been used to trace them back to their respective firn fields. The main glacier and the tributary glaciers are today static. Bjørnbo Gletscher is therefore characterized by both static and moving phases, and its dynamics are the same as those of surging glaciers. The quiescent phase is estimated to have been about 100 years. The next surge will presumably occur around 1990,