Firn samples from a 20 m. deep pit were examined by pollen analysis methods in order to confirm the stratigraphy of the annual net accumulation back to 1949. The late summer horizon separates the overlying winter layer with a small pollen content from a firn layer with a large pollen content. There are also differences in the spectra of the species which enable a seasonal separation of the layers. In addition, the mineral dust content was examined.

The terminus position of the Harald Moltke Bræ has been mapped from existing maps and from aerial and terrestrial photographs for the years 1946–47, 1954, 1956, 1962 and 1965. When abetted by Wright’s earlier work, a fairly detailed record of terminus position exists for the period 1916 to 1965. The glacier has been in nearly continuous retreat during this period interrupted by a slight advance from 1926 to 1932. Loss of area has been accelerating since 1946–47. Ice flow velocity near the terminus has fluctuated through a known range from 30 m./yr. to over 1,000 m./yr.

Ice thickness and resistivity of an Arctic glacier have been systematically investigated by the geoelectrical method. Further measurements were carried out on the ice cap. Favourable conditions for soundings were encountered, since the ice masses proved to be generally homogeneous, and there was a sufficient difference between the resistivities of ice and bedrock, while the surface layer differed only very little from the ice mass. A higher resistivity was found for bedrock than for the ice.

The force F required to separate two ice spheres was measured as a function of environmental temperature T, relative humidity H and the strength E of the external electric field in which the spheres were situated. It was found that over the entire attainable range of T and H, F increased rapidly with increasing E. The increased adhesion was not accompanied by an increase in the rate of growth of the ice bridge between the two spheres and is explicable in terms of Davis’s (1964) calculations of the purely electrostatic forces between two spheres situated in an electric field. The experiments indicate that the rate of growth of snowflakes in a cloud by means of ice crystal aggregation will be markedly enhanced if the cloud is highly electrified.

Attenuation of visible radiation by falling snow was studied by a method based on brightness contrast between topographic features and the adjacent sky. Extinction coefficient and visual range are related to bulk snow density, and are compared with data for Antarctic blizzards. Since attenuation depends more on the size and concentration of discrete particles than on the mass density of suspended snow, the process of particle aggregation and snow-flake formation during fall is considered by collision theory, and an expression describing aggregation effects is developed. This offers an explanation for the relative constancy of particle concentration observed at ground level during snowfalls of varying intensity. Since there is no strong justification for relating extinction coefficient to snow density, an empirical correlation between extinction coefficient and precipitation rate is given for practical use. It is shown that visual range estimated by eye in hilly terrain may be less than the true value, since sky brightness is locally reduced over broad hill-tops with low albedo.

A lichen-growth curve has been developed for dating Recent glacial and periglacial deposits in the Indian Peaks area of the Colorado Front Range. Rhizocarpon geographicum was selected for the study because of its long life span and consistent size-age relationship. The species grows at different rates in different micro-environments, with moisture, stability of substrate and length of snow-free growing season having the greatest effect. Growth rates were determined indirectly, by measuring the maximum diameters of circular or nearly circular thalli growing on surfaces of known exposure age. Measurements were made on 24 historically dated surfaces, ranging in age from 25 to 69 yr., and on three radiocarbon-dated surfaces, including (1) mudflow levees younger than 180 yr., (2) a rock wall built by prehistoric Indians about 970 yr. ago, and (3) ground moraine deposited by a retreating valley glacier about 2,460 radiocarbon years ago. R. geographicurrz grows very rapidly (14. mm./100 yr.) during the First 100 yr. of its life. Growth then slows to an average rate of 3.3 mm./100 yr. The completed growth curve is believed to be suitable for dating deposits at least as old as 3,000 yr.

The sea ice in McMurdo Sound, Antarctica, is extensively utilized for runways, travel, freight hauling and docking facilities. The safety and efficiency of these operations depend upon a better understanding of the sea-ice bearing strength.

Variations in shear and tensile strength, decreased thickness, salinity changes, internal deterioration and changes of the temperature gradient are all related to and dependent upon snow cover, ambient temperatures and solar radiation. During the austral summer of 1964–65, shear strength decreased from 9.8 kg./cm.2 in October to 6.3 kg./cm.2 in late January and then increased to 8.0 kg./cm2. by 10 February. The salinity of collected brine decreased from 125 p.p.t. in November to 43 p.p.t. in January. Thickness increased until mid-December, then decreased rapidly by bottom melting until break-out in February. In the Cape Armitage shoal area, thickness decreased from 2.5 m. in mid-December to 36 cm. in late January. Snow cover significantly affects the degree of internal deterioration and the amount of strength loss during the summer. Sea ice with more than 6 cm. snow cover is consistently stronger than unprotected ice and deterioration is less. Bearing strength of the sea ice is sufficient for most ordinary loads throughout the period of most extensive use.

An attempt has been made to measure the D.C. resistivity of ice directly by placing plane–parallel samples between two electrodes with guard rings. Very strong polarization effects were observed which were most pronounced in ice from an ice–cored moraine, lesser in glacier ice, and the least in artificially frozen ice.

The net mass budget is estimated for the western part of the Ross Ice Shelf drainage system. The area of the system is (1.75±0.26) × 106 km.2, and the drainage periphery extends along the eastern flank of the Trans-Antarctic Mountains between lat. 77° 58′ S., long. 164° 37′ E. and lat. 85° 27′ S., long. 147°50′ discharge is estimated from vertical cross-sections and corresponding ice-movement data for eight outlet glaciers. Free-air gravity anomalies, corrected for the effect of terrain above the glacier surface, are used to determine cross-sections of valleys by comparison with theoretical gravity profiles for several two-dimensional valley models. These data provide a basis for estimating the rate of ice discharge from the plateau, which is compared with the estimated rate of net accumulation at the surface, to determine the net budget of the ice sheet in the region. Representative mean rates of ice discharge measured in different types of glaciers are approximately 0.25 × 1015 g. km.−1 yr.−1 in outlet glaciers with large basins, and 0.05 × 1015 g. km.−1 yr.−1 in outlet glaciers with small basins. Taking into account the snowshcd area and the rate of accumulation, the rate of ice discharge in cirque and piedmont glaciers is estimated at about 0.02 × 1015 g. km.−1 yr.−1 The difference ((48±29) × 1015 g. yr.−1) between mass input ((96±25) × 1015 g. yr.−1) and mass output ((48±15) × 1015 g. yr.−1) is large enough relative to the estimated standard error to indicate a probable positive net budget.

Walsh Glacier, Yukon and Alaska, after 40 years or more of virtual stagnation in the terminal area, began a very rapid surge in late 1960 or 1961. A maximum movement of 10.1 km. occurred in the central portion of the glacier between 1961 and 1965, as shown by aerial photographs of the displacement of surface features, perhaps the greatest such displacement yet reported for any surging glacier.

Velocity and ice-thickness profiles were measured un the western glaciers of the Sør-Rondane during the Expéditions Antarctiques Belges of 1959 and 1960 Some of the stations were re-occupied for velocity measurements during the Expédition Antarctique Belgo-Néerlandaise, Campagne d’Été 1964–65.

The profiles, with stations at 1 mile. (1.6 km.) intervals, were generally east-west and at right-angles to the direction of flow of the plateau outlet glaciers. The movement was measured by resection of each station from the main triangulation points over periods ranging from 256 to 1,501 days. Double ties with a Worden geodetic-type gravity meter were measured between the stations. An additional gravity station was occupied on rock at each end of the profile. The ice thickness and the subglacial topography are calculated from the gravity profiles. Combined with the surface velocity, they allow an estimate of the discharge of the glacier. The results indicate a close relationship between the glacier flow and the supply from the Antarctic Ice Sheet, as demonstrated by a study of the aerial photographs.

The pattern of accumulation on the Devon Island ice cap is described. There is an area of minimum accumulation encircling the highest part of the ice cap and 100–200 m. below it. Below this zone, accumulation gradually increases to a maximum near the ice-cap edge. The overall pattern is related to snow transport by katabatic winds. There is a regional accumulation pattern of high accumulation (ca. 40.0 cm. water equivalent) in the south-east part of the ice cap and an area of low accumulation (ca. 11 0 cm. water equivalent) in the north-west. This east-south-east to west-north-west accumulation gradient is related to cyclonic activity to the east in Baffin Bay, and it is probably intensified by the presence of open water in the same area.

This narrow, 600 m. long cirque glacier is apparently composed throughout of alternating layers of ice and sand that strike parallel to the edge of the glacier and dip into the glacier at an angle of 82°. The thickness of the sand layers averages 10 cm., and that of the ice layers 20 cm. The sand layers are generally composed of thin parallel laminations but micro-cross-bedding is present locally. The layers have been broken into angular blocks 0.5 to 3.0 m. long, separated by ice columns connecting adjacent ice layers. The ice layers show thinner zones of contrasting bubble content which bend into the columns separating the sand blocks.

The sand was probably blown into this cirque from the floor of Wright Valley 6 km. south-west and 1,100 m. below. Each pair of sand and ice layers may record accumulation during one year. The steeply dipping yet otherwise undeformed layers clearly prove that rotational movement has taken place. The breaking of the sand layers into blocks is the result of plastic extension within the glacier.

Two types of morainic deposits can be found in western Sør-Rondane mountains: the super-glacial morainic ridge the material of which comes from slope evolution, and the hillocky moraine whose origin is related to shear planes in the glacier and therefore subglacial. A hypothesis of the formation of the hillocky moraine is given and the lithological composition of this deposit allows us to deduce the importance of glacial erosion at the level of the ice falls which frequently exist at the beginning of outlet glaciers where they leave the polar ice sheet. On this step, the role of glacier fluctuations is of importance in relation to a special periglacial process: greenhouse frost shattering.

The growth modes of ice crystals in supercooled water and various aqueous solutions were studied at different supercoolings by a motion-picture technique. ln pure water contained in plastic capillary tubes, ice dendrites formed which at supercoolings between 1 and 4°C. grew parallel to the tube axis. At supercoolings larger than 4°C. the direction of growth was inclined to the tube axis such that the dendrites hit the tube wall and afterwards proceeded growing in a new direction. As a result it appeared that the ice crystals grew in a zig-zag or screw fashion. This growth mode became enhanced when the supercooling was increased or salts were dissolved in the water. In large water drops, ice dendrites formed which at supercoolings smaller than 1°C. were co-planar with the seed crystal and between 1° and 5°C. split into two dendritic segments. At supercoolings larger than 5°C. multiple splitting of the seed crystal was observed and this became strongly enhanced when salts were dissolved in the water. Tentative explanations for these results are given.

Unlike the other large lakes in the ice-free valleys of southern Victoria Land, Antarctica, Lake Vida, in Victoria Valley, is probably frozen to its base. Sand layers in the uppermost 11 m. of ice on Lake Vida may indicate that this lake has a different history from the others. Summer-time ablation is about 50 cm. of ice.

Dendritic aggregates of ice and brine formed upon freezing of aqueous solutions have been studied. Chlorides of sodium, potassium, lithium and hydrogen were used as solutes; structures produced on freezing of binary, ternary and quaternary solutions were examined. Effects of freezing rate, solute concentration, solute diffusivity, mixing of solutions and magnetic fields are reported.

The spacing between ice platelets or dendrites was found experimentally to be proportional to the square root of the freezing time when the freezing rate was constant from beginning to end of solidification. During unidirectional freezing from a constant temperature chill, the solution at each location is subjected to a spectrum of freezing rates; dendrite spacing increases linearly with distance from the chill surface and it is inversely proportional to the square root of the maximum freezing rate.

In binary solutions dendrite spacing increases linearly with solute concentration; above a critical solute concentration ice platelets develop side branches. Application of an external magnetic field has an effect similar to increasing concentration. At a given solute concentration, spacing between ice dendrites increases linearly with solute diffusivity.

In ternary and quaternary solutions dendrite spacing is a function of the concentrations and diffusivities of each of the constituent solutes.

A gravity survey was made in June of 1963 of four ice caps on western Melville Island, Canadian Arctic Archipelago. Ice thicknesses were interpreted from Bouguer anomalies at 138 stations. The regional gravity field of the area has a simple form and is associated with a uniform bedrock geology. Because of this, the interpretation of the gravity data was greatly simplified in comparison with the more usual glaciological problem. It was found that greatest ice thicknesses ranged from 30 to 50 m., filling hidden valleys or depressions under the main ice-cap body. Ice-cap volumes ranged from 0.2 to 1.0 km.3.

Observations on both the modern and Pleistocene snow lines were made during a journey through the Peruvian Andes. En route observations were supplemented by an evaluation of air photographs in the Servicio Aerofotográfico Nacional in Lima and a survey of the literature. The large-scale variation of the Pleistocene snow-line depression is discussed with respect to possible palaeoclimatic implications.