A device is described which automatically measures the thickness of a floating ice cover at regular or any desired times and allows the result to be printed together with the time on a shore-based recorder. This instrument has been proven by a year’s operation near Mawson, Antarctica.

If the surface of Berendon Glacier, British Columbia, Canada, rose by 19 m above its 1963 level at a certain point near the terminus it would reach the entrance to a mining tunnel. Computations are made to see whether this is likely in the near future.

We calculate the changes in mass balance that would be necessary to make the glacier, which is now retreating, start to advance and reach the tunnel in 40 years and 20 years respectively. The method fits polynomials to the advance—retreat data and then uses the λ coefficients of Nye (1963[b]) to infer the corresponding mass balance behaviour. It is concluded that if the mean mass balance should increase smoothly to +70 cm/year, which is a high but possible value, by the year 2003, the ice would reach the tunnel portal in 2003. But, even assuming a rather drastic deterioration in the climate in the future and a concomitant increase of the mean mass balance, the ice will not reach the tunnel portal within the next 20 years.

The problem of erratic boulders lying far from their place of origin attracted considerable attention during the closing decades of the eighteenth century. More especially, interest focused upon the blocks of Mont Blanc granite resting on the flanks of the Jura. Various fanciful explanations, ranging from debacles to gigantic explosions, were offered to account for such phenomena (some of the early explanations have been reviewed by Agassiz (1840) and North (1943)) but the true explanation long eluded even the most astute observers. It was not that there was a failure to appreciate the transportive power of glaciers—de Saussure (1786–96, Vol. 2, p. 21) and others recognized the ability of glaciers to move large boulders—but a failure to recognize that glaciers had recently extended far beyond their present limits.

Well-developed elevated beaches. deltaic deposits, marine-boulder pavements and wave-washed bedrock surfaces are found from Cape Bernacchi north to Granite Harbour. The highest measured marine feature, an elevated beach at Dunlop Island, is 20 m (67 ft) above sea-level. The highest beaches at Marble Point and Cape Roberts, about 48 km (30 miles) apart, are about 20 m (66 ft) above sea-level. The marine limit between these two points is, therefore, essentially horizontal. The highest beach at Cape Bernacchi. approximately 4.8 km (3 miles) south of Marble Point, is about 12 m (40 ft) above sea-level, Well-developed elevated beaches disappear about 3.2 km (2 miles) south of Cape Bernacchi and are not found between this point and Koettlitz Glacier.

These beaches post-date the youngest glaciation recognized in the lower Wright Valley. A 14C analysis of an elephant seal buried in a 13 m (44 ft) beach at Marble Point indicates that this beach is 4450 ± 150 years old. As sea-level at this time was approximately 3 m (10 ft) lower than at present. the Marble Point area has risen isostatically about 16 m (54 ft) during the last 4450 ± 150 years.

Pitted beaches, beaches deposited on ice, a buried elephant seal and gravel ridges deposited by ice indicate that all of the beaches were formed in a climate like that now found in the area.

The deformation and the state of stress in the frontal part of a floating glacier is analysed by a method analogous with the beam theory, applied in engineering practice for determining stresses and deflections of a beans of an elastic material. Very rough approximations are made, the most severe being that of assuming the viscosity of the ice constant. Curves showing the progress in time of the deflections and the stresses in the frontal part of the glacier are given for the case of an infinitely wide glacier. The curves show, that the stresses are greatest at a cross-section situated at a distance of about the thickness of the glacier from the front, and that the stresses are of a magnitude which very likely will lead to fracture, resulting in the formation of an iceberg. It is shown that the magnitude of the icebergs as well as the frequency of the calving is a function of the thickness, the density, and the temperature of the glacier. Observations from nature supporting the theory are described. Finally other calving mechanisms for floating glaciers are briefly discussed.

The steady profile of a finite-amplitude kinematic wave on a glacier is calculated with the assumption that the wave velocity varies linearly with h1, the departure of the ice thickness from the datum state. If the flow of ice is due mainly to sliding of the glacier on its bed, the width of the calculated steady profile is several hundred times the datum state ice thickness. The width of an observed kinematic wave front on Nisqually Glacier, Mt. Rainier, Washington is at least an order of magnitude smaller than the calculated steady profile. This indicates that the observed steepening of the wave may be due to effects other than variation of wave velocity with ice thickness.

Rectangular specimens of ice (c. 5 cm × 2 cm × 0.5 cm) were cut from large single crystals (c, 10 cm × 5 cm2) grown from pure water by a modified Bridgman technique. When these specimens were deformed under controlled conditions, slip lines which were predominantly parallel to the basal plane became visible. In some cases short. perpendicular segments were also seen which can be interpreted as evidence for cross-slip in ice. Measurements of slip-band spacings were made on silvered “formvar” replicas of some deformed crystals. These measurements showed that “coarse” slip occurred when the resolved shear stress on the basal plane. σ, was greater than about 0.2 bars, and that the average thickness of the slip lamellae, d (cm) was approximately given by Wakahama’s relationship. (σ−0.2) d = 0.45 × 10−3. At lower stresses “fine” slip occurred, and the relationship between the average thickness of the lamellae and the resolved shear stress was more adequately described by Taylor’s formula, σd = 7.2 × 10−5. It is. however, possible that both coarse and fine slip occurred at higher stresses, but that the fine slip was then below the limit of resolution.

A block of ice from Blue Glacier. Washington, was successively sectioned at close intervals as a means of determining exact crystal shape in three dimensions. Two crystals occupying over 20 per cent of the entire sample are used as examples, and their volumes calculated. These crystals were found to be much larger and more complex in shape than expected from thin-section examination alone. The surface-to-volume ratio was calculated using a simple relationship between the length of lines in a grid crossing the crystal and grid-line intercepts with the crystal boundary. From this ratio the surface area of each crystal was calculated.

A measurement of irregularity or jaggedness is introduced in order to compare crystals of different size with one another. This is necessary because surface-to-volume ratio of a body of the same shape decreases as the size increases.

Hot-point drills are practical for producing holes in glaciers for ice-thickness and temperature measurements, as well as other glaciological studies. Buoyancy stabilization assures a vertical attitude of the drill and a plumb hole. This is achieved by designing a drill with a heavy hot point and a light upper section which is buoyant in the surrounding melt water. The buoyant force is less than the weight of the drill in air but its rectifying moment about the fulcrum (the tip) is greater than the tilting moment of the drill weight. Two methods to prevent refreezing of the melt water are proposed in order to permit drilling in cold ice and to assure continued access to the hole.

A recent field comparison of snow strength as measured by the snow resistograph and compressive strength as measured by direct loading to failure indicates good agreement in the range 25–400 g/cm2.

Data on the physical properties of seasonal alpine snow have been collected from the Beartooth Mountains near Cooke City, Montana (elevation ≈3000 m) and the Bridger Range near Bozeman, Montana (elevation ≈2200 m). Systematic measurements of snow density, temperature, structure, ram and Canadian hardness, centrifugal tensile strength and shear strength measured with a shear box and several types of shear vanes are included. Test results were grouped according to gross snow types (cohesive fine-grained “winter” snow. depth hoar, new snow, etc.) and whether the snow was wet or dry. Then interrelations between the different test parameters were studied. A plot of ram number versus density for winter snow gave a log-linear relation similar to that suggested for polar snows. Both shear-vane and centrifugal-tensile results when plotted as a function of porosity are well described by the negative exponential relation suggested by Ballard and Feldt. Depth hoar and wet snow invariably have lower strength values at any given density. There is an excellent one-to-one agreement between values obtained with the shear vane and the shear box.

Several field experiments were performed to study the sources of error in making in-situ mechanical tests on snow without utilizing a pit wall. Statistical analysis of the results shows that the main factor contributing to the experimental scatter is lateral inhomogeneity in the snow cover. There was no significant difference between the results of different operators. The standard deviation of a group of strength tests is shown to be directly proportional to the mean value of the group. This indicates that a logarithmic transformation should be made in handling snow strength results in order to stabilize the variance. It is emphasized that the systematic relations between snow properties invariably become obscured when different snow “types” are indiscriminately grouped together.

The rate of snow accumulation has been measured at the U.S.S.R. station situated at the Pole of Relative Inaccessibility (eastern Antarctic plateau). Five independent methods were used. The results, expressed in g cm−2 year−1, are as follows:

1. (1) Accumulation-stake measurements show an accumulation of 3·1±0·5 in 1965. A maximum value of 3·6 for the 6–year interval 1959–65 is derived from snow-thickness measurements.

2. (2) Firn stratigraphy was found difficult to interpret in terms of annual layers. An upper limit of 12 g cm−2 year−1 is suggested.

3. (3) 18O/16O ratios were measured along the upper 235 cm. Assuming that each maximum in the isotope profile corresponds to a summer season, the accumulation would be 8·6±0·9.

4. (4) Gross β radioactivity as a function of depth was measured on three firn sections. The 1955 radioactive fall-out horizon is clearly marked, enabling the derivation of an average accumulation of 3·0±0·3.

5. (5) The average accumulation over the last 80 years, derived from the 210Pb distribution with depth, is 3·1±0·3.

A multi-annual average accumulation rate of (3·0±0·3) is thus firmly established, as well as the validity of both the 210Pb method and the 1955 radioactive fall-out horizon method. Stratigraphie studies lead to uncertain results. Oxygen isotope variations give accumulation values which are too high by a factor of two at least.

Accumulation values of the same order of magnitude (2·8±0·2) were derived from radioactive fall-out measurements at the U.S. “Plateau” station.

The movement of the Irish Sea glacier is discussed for the St George’s Channel sector during the last major glaciation. It is considered that the ice was already diverging when it crossed Pembrokeshire, after passing through a constriction farther north. This constriction was probably caused by local Irish ice in the west and local Welsh ice in the east. In view of this, it is suggested that the Cardigan Bay coasts could not have been ice-free during the last glaciation.

Radiometers, suspended at a height of 15 m between two towers anchored to the bottom of the ice cover, have been used to measure the average or integrated albedo of the surface. The work was carried out in May 1967 at Tanquary Fiord, Ellesmere Island (lat. 81° 25′ N., long. 76° 50′ W.) during the period when the surface of the ice cover was undergoing rapid change. The albedo was observed to have a value of almost 1·0, for a fresh snow cover, and about 0·8 for a weathered snow cover. It decreased to 0·6 as the wind partially cleared the surface of snow and gradually to 0·5 with further deterioration of the snow. The onset of melting, produced when the daily mean temperature exceeded 0°C, rapidly lowered the albedo to a value of about 0·3.

Sub-surface melt pools were discovered during construction of an airfield located on glacier ice in the western part of the McMurdo Ice Shelf, Antarctica. The melt pools occur beneath areas of blue glacier ice and they are impossible to detect by visual examination. They vary in size and shape but are usually 1.0 to 1.5 m deep and span circular areas 10 to 15 m in diameter. Sub-surface melting starts in mid-December at depths of 40 cm or more and it progresses until late January when refreezing begins. The ice cover over melt pools may thin to as little as 7 cm and this creates a serious hazard to aircraft operations.

The melt pools are caused by the greenhouse effect of intense solar radiation, low albedo of the blue glacier ice and heat absorption by rock particles and dust. The high-albedo layer of chipped ice and powdered ice that was produced during runway construction was completely successful in preventing sub-surface melting. The thickness of this protective layer appeared to be of little importance, providing it exceeded 3 cm.