An analysis is made of the time required to build up an ice-age ice sheet and of the time required to destroy such an ice sheet. The calculations are based on the approximation that the theory of perfect plasticity is valid. It is concluded that the time required to build up an ice-age ice sheet is longer than the time required to eliminate it. If it is assumed that the accumulation rate of an ice-age ice sheet lies in the range of 0.2 to 0.6 m./yr., it is found that the growth time of a large ice sheet is of the order of 15,000 to 30,000 yr. Ablation rates of to 2 m./yr. lead to shrinkage times of the order of 2,000 to 4,000 yr., provided ablation occurs over an appreciable area of the ice sheet.

At the head of a tunnel driven to bedrock in Blue Glacier, Washington, the mechanism of sliding of the glacier over bedrock has been investigated. This mechanism involves (1) regelation-slip, which operates through the combined action of heat transport and mass transport (liquid and solid) in the immediate neighborhood of the glacier sole; (2) plastic flow, promoted by stress concentrations in the basal ice. We have observed and/or measured the following features of the basal slip process: 1. Slip rate in relation to internal deformation of the ice; 2. Time-variations of the slip rate; 3. Freezing of basal ice to bedrock upon release of overburden pressure; 4. Formation of a regelation layer in the basal ice, and detailed behavior of this layer in relation to bedrock obstacles and to incorporated debris particles; 5. Local separation of ice from bedrock and continuous formation of regelation spicules in the open cavities thus created; 6. Plastic deformation of basal ice as recorded in the warping of foliation planes and of the regelation layer. Simple experiments to test our interpretation of the regelation layer have been carried out, in which regelation flow of solid cubes of different materials frozen into blocks of ice was produced. The field measurements and laboratory results are used to test the theory by Weertman (1957, 1962) of the basal slip mechanism. It is found that the theoretical “controlling obstacle size” and “controlling obstacle spacing” that should correspond to our observations are about an order of magnitude too small. This quantitative failure represents an overemphasis in the theory on the importance of plastic flow as compared to regelation. A new theory has been constructed which gives results in better agreement with observation.

Measurements have been made of the flow rates of two adjacent glaciers in Westland, New Zealand. A longitudinal flow foliation is developed in one (Franz Josef Glacier) and this was found to be associated with more or less constant rates of flow down the length of the glacier tongue. In the other (Fox Glacier) the foliation is of the transverse type and is associated with a high strain-rate in ice under compression with markedly decreasing rates of flow being found down the length of the glacier. The highest strain-rates are associated with tectonic dirt bands and thrusts.

A highly deformed area in the Ross Ice Shelf near the Bay of Whales was studied during the 1958–59 Antarctic summer season. A series of snow-firn folds up to 8 m. high and with a wavelength of approximately 100 m. occurs here. Along one of these folds, a unique ice layer formed during the 1952–53 season through refreezing of melt water. From sites along this layer approximately 2,300 ice grains were measured using the root mean square method with the least circle diameter. The data obtained indicate the following:

1. The mean diameter of the ice grains ranges from 4.5 mm. in the ice from the crest of the anticline to 2.5 mm. in the zone of maximum shear stress and/or in sections having a high air bubble content.

2. The large diameter of the ice grains at the crest is attributed to greater solar radiation resulting from their proximity to the 1958–59 snow surface, and because they are near the surface of the exposed crevasse wall.

3. The area of maximum shear stress, which is represented by small ice grains and the presence of secondary folds, is located almost halfway between the crest and the trough.

4. Grains in the trough are larger than those in the shear zone because of less stress, and smaller than those at the crest because of deeper burial and the presence of a crevasse bridge which eliminates all direct radiation here.

5. The growth of the ice grains is therefore controlled by temperature, stress and impurities.

The pattern of flow of moraine-carrying glaciers is studied by models whirled in a centrifuge. Because of the rather high centrifugal force (1,000 g), substances with high viscosity, such as bouncing putty and stitching wax (viscosity around 106–107 poises), can be used as glacier-imitation materials. As moraine-imitation material powdered hard wax is used. The strength and high viscosity of the model materials permit detailed structures to be studied without the disturbing effects of sagging after being run to the chosen stage in the centrifuge. Stroboscopic light makes it possible to follow the evolution of the flow and to stop the centrifuge and thus the flow at any stage.

Rather realistic-looking fold structures of the kind seen in some piedmont ice sheets develop readily after a few minutes’ run in the centrifuge.

The mechanism of fold evolution is discussed.

No slip (or shear) has taken place along a “foliation” which sometimes develops parallel to the axial planes of the folds.

A commonly accepted distinction between snow-patches and glaciers is the slow mass movement of the latter with consequent abrasion of stones and rock surfaces. However, the observations of some workers do not support this distinction. The present study, in a snow-patch area on Mount Twynam in the Snowy Mountains (Australia), presents positive evidence of slow mass sliding of snow, causing transport, abrasion and detachment of stones and abrasion of the bedrock surface. Consequently, no sharp separation is possible between the erosional effects of snow-patches and small cirque glaciers. In areas such as the Snowy Mountains the relative importance of glacial and nivational processes becomes more difficult to evaluate.

The ice movement on the Byrd Glacier, Antarctica, was measured as function of time, on the basis of aerial photography. The method of aero-levelling strip triangulation with a minimum of geodetic control was applied. The methods and procedures were verified over Laufen-Bauma test area.

Observations in a deep mine working which reached the base of a valley glacier some 150 m. below the ice surface indicated an initial cold and impervious condition at and near the ice–rock contact. Later, however, an excellent hydraulic connection with free water in the upper layers of the glacier was established, perhaps by the thawing of a passage upward through the ice by warm water escaping from the mine. Subsequent records of water levels, or of water pressures, within the mine, reflecting conditions in the upper part of the glacier, show periods of moderately steady conditions, at times showing slight diurnal fluctuations, interrupted by irregular and catastrophic surges, particularly during periods of rapid snow melt and heavy rains. A seasonal cycle in pressure is suggested by the record.

The custatic changes of the ocean in prehistoric and historical times are linked with the fate of the ocean-based salt industry, and are recognized as erratic. An hypothesis is proposed to explain these erratic changes with albedo changes of the polar ice sheets, caused in turn by erratic volcanic dust fall-out. Ash layers in Antarctic ice cores are connected with historical dislocations of maritime civilizations.

Albedo changes associated with the dusting of ice sheets are considered to be the cause of the decline of periods of glacierization generally. Such albedo changes are connected with volcanic activity on the one hand, and loess formation on the other, caused in turn by the growth of the ice sheets.

In the Kumaon region of the outer Himalayas there is a chain of lakes which, on the basis of various features, were previously thought to be of tectonic origin. A detailed geological study of this area carried out in June 1961 revealed the presence of morainic deposits in the vicinity of the lakes, and it is now considered that they are essentially of glacial origin.

Published data on the creep of polycrystalline ice and crystals oriented for non-basal slip are discussed in terms of theories of prismatic slip in hexagonal metals. It is concluded that creep of polycrystalline ice near the melting point is controlled by non-basal slip but a decision on the exact mechanism of slip cannot be made on the basis of available data.

Equations and a graph are presented for calculating gravity anomalies on a two-dimensional glacier model having a horizontal upper boundary and a lower boundary which is a parabola with a vertical axis of symmetry.