The lecture was a review of the research work carried out by the author and his collaborators, as well as by J. Gjessing and students working for their final degree. Attention is called to the existence of local centres in western regions even during the maximum of the last glaciation, as well as the transition from down-wasting of dead ice near the ice divide to backward melting of partly active glacier tongues in the high mountains near the sea. Regional reconstructions of the waning of the glacier ice are attempted.

In the approximately so m. thick ice cap of the Jungfraujoch (3470 m. above sea level), where the temperature throughout lies below the pressure melting point, continual measurements of displacement and deformation were carried out inside ice tunnels from 1950 onwards. These give an insight into the process of movement, the formation of water-filled crevasses and the relationships of viscosity in a cold ice cap glacier.

The plastic behaviour of the cold ice was examined through alterations in length of individual tunnels, and also through measured distortions of cross-section in circular sections of tunnel. Since the mean ice temperature in the region of the ice tunnel lies approximately between −1° and −3° C., these examinations provide a welcome supplement to analogous measurements which were taken in circular tunnels in a temperate glacier (Z’Mutt tunnel). The approximate calculation of the plastic deformation of a circular tunnel was thus extended by the obvious transformation of solutions known from elasticity theory.

By means of a qualitative analysis of the state of stress of an ice cap, an attempt is made to account for the distortion and the formation of the cracks and crevasses which were observed. The occurrence of blue bands could be followed in statu nascendi. This paper serves as a primary orientation and publishes some initial results of the examinations which are to be continued and completed over a number of years. In addition to its potentialities for practical use, this study may be of interest in respect to the behaviour of cold glaciers of the Arctic and Antarctic. In a final section, therefore, some problems of the Greenland ice sheet are considered in the light of the preceding conclusions.

The growth of single crystals of ice for the study of plasticity has to be done with care, since a disturbing lineage structure is easily generated. The orientation of specimens can be found from growth figures (dendrites) and Tyndall’s “flowers”; these give the a-axis, as the branches in both cases point in the [1120] direction. Slip occurs on the basal plane without following a definite glide direction. In pure shear two stages of creep exist, the first for a glide of 10–20 per cent in an undeformed crystal, the second for greater shears having a higher creep velocity. Both stages obey the law , n being 2.3–4 in the first case and 1.3–1.8 in the second. The deformed state above the transition remains stable and no recrystallization takes place in pure shear. Restoration of the undeformed state by recrystallization occurs only in inhomogeneously deformed parts. This observation may have an influence in interpreting measurements of glacier movements and tests on polycrystalline specimens in the laboratory.

The Penny Ice Cap on the Cumberland Peninsula of Baffin Island, N.W.T., Canada, was studied during the summer of 1953. This ice cap has an area of some 5900 sq. km. and rests on a 2000 m. high mountain range. It has ten major outflowing glaciers, three of which reach the sea in fjords. The progress of snow accumulation and ablation and the net annual loss or gain of water at various altitudes on the ice cap are recorded. The firn line is at about 1550 m. and the outflowing glaciers are noticeably retreating.

Description of a horizontal tunnel driven through a cold, steeply sloping glacier, altitude 14,000 feet (4267 m.) on Monte Rosa, from its surface right through to bedrock, a distance of 302 feet (42 m.). Temperatures found deep within this cold glacier were 18° F. (−7.78° C.) compared with 8° F. (−13.33° C.) near its surface, and again near contact with its rock bed. This internal heat is interpreted as heat supplied from the interior of the earth, and as indicative of existence of ice at pressure-melting-point in all cold ice glaciers, if thickness of ice is sufficient. Existence of such an underlay of ice at pressure-melting-point, varying in distribution with varying supply of internal heat, is shown to explain (1) cirque erosion, (2) uniform elevation of cirques in any one region, (3) existence of extrusion flow under certain conditions, and (4) control of cycles of continental glaciation, under extreme limits.

Two tunnels were dug through a small cirque glacier to the rock wall behind (a) the névé, and (b) the lower glacier. The upper tunnel revealed shattering of the rock wall due to the freezing of melt water. The bedrock at the end of the lower tunnel was both smoothed and fractured. The problem is to account for the fracturing of the resistant gneiss where the temperature remains at 0° C. throughout the year. The solution offered is that the release of pressure beneath a thick glacier immediately downstream from a roche moutonnée, or from a small steep step, enables the stresses locked within the gneiss to crack the rock. These stresses result from the gradual removal of the overburden, since the gneiss consolidated under the pressure of thousands of metres of rock strata. The glacier can later remove the jointed and broken rock.

A method is described of determining the thickness of a valley glacier from measurements of gravity. On a Norwegian glacier approximately 4 km. long and km. wide values of gravity were measured at points on four transverse lines. For comparison, values were measured at points on three lines in the valley below the snout of the glacier. The positions and altitudes of these gravity stations were determined by triangulation. After making corrections for the altitudes of stations and for the effect of the valley walls, the differences between the gravity values obtained on the glacier and those obtained in the valley below the glacier are attributed to the thickness of the ice. Four transverse sections of the glacier, obtained in this way, are given. Errors in the estimates of ice thickness should not exceed 20 per cent on the two lower cross-sections, nor 40 per cent on the upper two.