Some generally accepted views on joints in rocks, particularly exfoliation joints, are summarized. Lewis’ pressure release hypothesis is assessed in relation thereto. An additional hypothesis is suggested whereby the existing stress system in rocks due to the removal of overburden which would favour exfoliation, would be augmented by freezing of the saturated rock when the ice retreats, so triggering this type of extension joint.

A review of the inadequacies of the glacial moulin hypothesis for the origin of potholes.

An unusual opportunity for the study of glaciers in the process of development is afforded in Katmaicaldera in south-western Alaska. A violent eruption in 1912 destroyed the summit of glacier-clad Mount Katmai, creating a caldera 4 km. wide and 800 m. deep. Ice cliffs produced by beheading of the glaciers have since thinned and shrunk away from the rim of the caldera, except in the south-west. There, local reversal of direction of movement has resulted in an ice fall which descends part way down the crater wall. In the past thirty years two small glaciers have formed, near 1525 m. above sea level, within the caldera on large masses of slumped wall-rock below the north and south rims respectively. Elsewhere the sheer walls of the crater descend so steeply to the level of the caldera lake that permanent snowbanks cannot accumulate. The lake, which continues to rise at a rate of more than five meters per year, is at present the primary deterring factor in glacier development in the caldera.

On aerial photographs of the Patagonian ice fields several types of bands can be identified; (1) fine ogives similar to Lüder’s lines in metals; (2) dirt bands which are both the outcrop of the annual debris strata of the névé and melt borders (the Schmelzrände of von Klebelsberg); (3) annual wave ogives below some ice falls; (4) annual ogives in regenerated glaciers, the formation of which is studied; (5) large melt borders which occur at longer intervals as a result of volcanic eruptions. These latter give evidence on the volcanic activity in the middle of the Patagonian ice fields.

A general description of ablation polygons is given and variations from widely distributed regions are examined. After discussion of the conditions in which they most frequently develop, possible explanations are considered, leading to the conclusion that the polygons result from ablation by turbulence in the surrounding air, and that the dirt fringes to the polygons may be explained by the “normal trajectory” theory.

A model is proposed to explain the sliding of any glacier whose bottom surface is at the pressure melting point. Two mechanisms are considered. One is pressure melting and the other is creep rate enhancement through stress concentrations. Neither of the mechanisms operating alone is sufficient to explain sliding. If both mechanisms operate together appreciable sliding can occur.

The problem of the creep deformation of floating ice shelves is considered. The problem is solved using Glen’s creep law for ice and Nye’s relation of steady-state creep (the analogue of the Lévy-Miles relation in plasticity theory). Good agreement is obtained between an observed creep rate at Maudheim in the Antarctic and that predicted from the results of creep tests made by Glen.

The “old moraines” of Pangnirtung Pass were constructed by trunk glaciers, tributary glaciers, glacial streams, rockfalls, talus-creep and other agents and processes. Rivers have since reworked or removed the deposits lying along the axis of the Pass and have begun to dissect the remainder. The old moraines have ice cores, which have tended to melt, collapse and flow downhill, thus further complicating the drift topography. The freshness of many old-moraine fronts implies a recent warming up of the climate, which is also reflected in the decay of the modern giaciers; but erosional undermining may also cause fresh fronts. Although no accurate date can be assigned to the disappearance of the trunk glaciers, A.D. 500 is given as a tentative estimate. There have since been at least two main advances of the tributary glaciers, of which the first followed close on the disappearance of the trunk glaciers and the second occurred not later than 1850.

This paper presents a preliminary account of the glaciological observations made by the Antarctic Expedition of the U.S.S.R. Academy of Sciences in Kaiser Wilhelm II Land, Queen Mary Land and Knox Coast in 1956. The topography of the edge of the ice sheet is described, and the ice regime is discussed, particularly in relation to the existence of ice-free areas such as “Bunger’s oasis”.

Results of observations on several glaciers in the Kongsfjord area are described, and comments are made concerning accumulation and ablation, glacier flow and the variation of glacier fronts. The findings are compared with those of previous workers in this district and, in particular, with those of H. W. Ahlmann. A history of the fluctuation of several ice fronts during the present century has been compiled from various sources, and some observations dating back to 1837 are mentioned.

To test Nye’s formula relating maximum surface slope at a point on an ice sheet with the thickness at that point, observations were made of the surface slope in north Greenland. Values of the shear stress on the bed at these points are calculated. It is unlikely that variations of the shear stress can be related with rates of movement. It is suggested that the difference between values of shear stress in north Greenland and those in south Greenland is at least partly due to the presence of bottom melting in the north.

This paper gives a brief account of the results so far obtained in research in Czechoslovakia on the crystallographic, stratigraphical and thermal properties of snow cover, and the use of these data in avalanche investigations. Avalanche danger is predicted by comparing the penetration resistance of snow layers, measured with a rammsonde, with resistance graphs of typical avalanche situations.