Accumulation on the Meighen Ice Cap appears to be about normal for the region, but ablation seems abnormally low. Statistical analyses of several years’ data reveal the following trends: accumulation increases towards the north; ablation decreases with increase of elevation, decreases towards the north and west, and is greater on south-facing slopes than elsewhere. Because ice movement is very small, these trends explain the surface topography of the ice cap quite well. Other topics discussed are the significance of changes in the margins of a stagnant ice cap, and the rate at which net mass balance changes with elevation.

The lower one-third of “Sioux Glacier” in south-central Alaska was buried beneath a debris slide during the 27 March 1964 earthquake. Investigations to determine the effect of this cover on the regimen of the glacier revealed that it has increased in thickness by as much as 28 m, primarily as a result of the insulating effect of this debris cover. In areas where debris has continuously veneered the surface, at least since 1938, the ice is also thicker. A longitudinal profile reveals that the area near the upper extent of the slide debris has become intensely crevassed and has been lowered as much as 8 m between 1965 and 1966, while the terminal area is up to 5 m higher and is characterized by thrusting. It is concluded that a kinematic wave passed through this glacier sometime between 1965 and 1966.

The upper zone of debris-veneered ice is moving at 175 m/year while the terminal area is flowing at only 21 m/year. The rate of down-glacier decrease in velocity is about 0.06 m/year per meter of horizontal distance except for an area approximately 1 km from the terminus. Here, the rate of decrease in velocity is 0.1 m/year per meter. The change in rate is presumed to be related to topographic control caused by the recent thinning of the ice here.

D.C. ice-resistivity measurements on the polar Paris Gletscher in East Greenland are presented. It is found that the observed profile is well described by a four-layer system. Near the surface there are two layers resulting from the penetration of the summer temperatures into the polar ice. Below this the ice has constant resistivity until the bed is reached, where contrary to expectation a high-resistivity layer is found.

Forbes Glacier, one of the outlet ice streams from the Antarctic ice sheet, is located 20 km west of Mawson, Mac.Robertson Land, east Antarctica. In the uppermost part of the glacier near Casey Range, the velocity at the centre of the glacier is 59 m year−1 and the strain-rate at seven strain grids ranges from −6.7 to 6.7×10−3 year−1 on the surface of the glacier. The fabric types of this area are characterized by single-maximum and small-girdle fabrics. It is confirmed that the single-maximum fabric is an original pattern which changes gradually to a small girdle fabric about the maximum compressive axis in association with grain growth. The patterns predicted by Brace (1960) can be adapted to the small-girdle fabrics of this area.

Several analyses are given for the flexure of a floating polar ice tongue with the general dimensions of several kilometers wide by 200 in in thickness. The lengths considered are from 2 km to in excess of 10 km which is referred to as a long slab. The analyses are made under the separate assumptions that ice behaves as (1) an elastic material, (2) an elastic-plastic material, and (3) a fully plastic material, when reacting to flexure due to changes in sea-level. The elastic analysis shows that hinge-line stresses could become very high of the order of 15 bar) for slab lengths up to about 3·5 km reacting to sea-level changes of the order of ±50 cm. For slab lengths greater than this, the stresses at the hinge, as well as being significantly less than before, become independent of the length of the slab, dependent only on the slab thickness and the amount of deflection of sea-level. In the elastic-plastic analysis, the hinge-line stress cannot exceed a value of about 2 bar. This yield value is reached when sea-level departs about 50 cm from the mean. The fully plastic analysis requires more accurate knowledge of the constants in the flow law and their variation with density, temperature and salinity within the ice. However, the theory may be tested by measuring the diurnal change in strain-rate across the hinge-line zone. The process of calving of large tabular icebergs from such glacier tongues may demand sea-level changes of more than ± 1 m, or bending about more than one axis of the shelf.

Measurements of the attenuation of acoustic waves in sea ice at frequencies f between 10 kHz and 500 kHz have been made on the ice cover at Tanquary Fiord, Ellesmere Island (lat. 81° 25′ N., long 76°50′ W.). A horizontal transmission path at a depth of 4 ft (1.3 m), mid-way between the top and bottom surfaces of the ice cover, was used at ranges varying from 25 ft (7.6 m) to 4 ft (1.3 m) between piezoelectric transducers immersed in oil-filled bore holes. The attenuation coefficient α was found to fit the equation a α = c1f+c2f4 with c1 = 4·45 × 10−2 db m−1 kHz−1, and c2 = 2·18 × 10−10 db m−1 kHz−4. Over the frequency band covered, the linear term was predominant and the Rayleigh scattering term relatively insignificant.

Continuous measurements of incident and reflected short-wave radiation have been obtained from 12 May to 17 June 1968 on the ice cover at Tanquary Fiord, Ellesmere Island (lat. 81° 25′ N., long. 76° 50′ W.). The observations were made with radiometers suspended between two towers at a height of 50 ft (15 m) to sample an area large enough to be representative of the surface of the ice cover. From the start of surface melting, time-lapse photographs were taken at intervals of 3 h with a camera mounted on one of the towers at a height of 20 ft (6 m) and slanted below the horizontal.

Values are presented, for the observation period, of incident short-wave radiation, albedo, air temperature at screen height and percentage of surface covered with melt pools. It is shown that the albedo decreases linearly with increasing area of water puddles.

Detailed observations on a collapsing kame terrace indicate that the terrace is being reshaped by: slumping and sliding of debris into depressions, melt-water erosion on the side of the terrace, debris flows in the gullies, and stagnant-ice bursts, a phenomenon analogous to a glacier burst except in the mode of formation of the water. Temperatures in the gravel over the ice, where the gravel is about 4 m thick, indicate that the rate of melting of the upper surface of the ice due to conduction may be as high as 24 cm year−1. Highest temperatures in the gravel were recorded during periods of heavy rainfall.

Modified versions of in situ strength tests previously applied to metamorphosed snow were developed to measure the mechanical properties of newly fallen snow during storm periods. A large drop-cone penetrometer, protected from the wind by an aluminum shell, was used to determine snow “hardness”. A lightweight model of the Haefeli ram penetrometer measured “ram numbers”. Shear strengths were obtained from large, light-weight frames. Some preliminary tests were made with a shear vane driven by a torque wrench. A new technique was devised for measuring tensile strength whereby a cantilever beam of snow is undercut until it fails under its own weight. Comparisons between the cantilever test and the shear-frame test show high ratios for tensile to shear strength. Cantilever strength plotted against density shows an order of magnitude variation in strength at all densities.

Simultaneous measurements were made of bot the strength and structural properties of a dry, seasonal snow-pack. The densities of the snow studied ranged from 126 to 407 kg m−3. The mechanical strength of this snow as determined by insitu shear-wave test and a centrifugal tensile test increases exponentially with the increase in size of intergranular sands. Bonding increases at a rate substantially greater than that predicted by the classical sintering equations. It is suggested that this is due to the wide variety of stresses present in snow with these relatively low densities.

Slab avalanches are shown to be released by brittle fracture. An analogy is drawn in which the snow-pack is considered to be a macroscopic, molecular model of glass. The analogy is examined qualitatively from two viewpoints: the Griffith fracture criterion, and stress concentration theory. The details of fracture propagation in a layered snow-pack are explained by means of stress concentration theory, and many details of slab avalanches are shown to be consistent with the proposed mechanism. The significance of various fracture surface markings is pointed out.

Results obtained from tensile and compressive tests on pure ice single crystals at various temperatures down to −90°C are reported. At −50°C tensile creep tests give a continually increasing creep rate until fracture, as observed at higher temperatures. The stress dependence of the strain-rate is discussed. Fracture stress increases with decreasing temperature. Results from constant strain-rate compressive tests are compared with theoretical curves computed from Johnston’s (1962) theory of dislocation multiplication. A dislocation velocity of the order of 0.5×10−8 m s−1 is deduced for ice at −50°C.

Surface topography of etched ice crystals was examined by a scanning electron microscope in combination with a Formvar replica method. The deep focus of the scanning electron microscope allowed observation of the sharply three-dimensional topography of ice surfaces. Various useful information was obtained from microphotographs of etched basal and prismatic planes, fractured surfaces, and grain boundaries formed between microcrystals of ice.

An alternative origin and significance for kettle holes is considered. Kettles among some kame tracts may be due not to melt of buried ice but rather represent the location of ice pillars or roof pendants among stratified subglacial deposits.

Glaciar Yanasinga (lat. 11° 36′ S., long. 76° 12′ W., 4850 m a.s.l.) is probably one of the few glaciers in the equatorial region on which measurements have been performed during the last 24 years. These were carried out in the years 1944, 1945, 1946, 1947, 1948, 1949, 1957, 1963 and 1968. The results of these surveys are presented on a map and references are given for those interested in obtaining more detailed information.