Measurements of the annual snow accumulation have been made at many points on a traverse of north Greenland. In lat. 77–78° N. the annual accumulation above 1800 m. was about 13 gm. cm.−2 in the years 1948–53 and, in contrast to results which have been obtained further south, did not vary with longitude. In 1953–54 the accumulation was greater. The annual accumulation in north and central Greenland has varied significantly over the last 50 years, but similar variations are not shown in the precipitation records at coastal stations. Using all the available information, the mean annual accumulation on the Greenland Ice Sheet has been calculated as 29±3 gm. cm.−2.

Mean annual air temperatures and precipitation on the Greenland Ice Sheet, as estimated from snow profile studies and long-term meteorological records at coastal stations, have been used to prepare mean annual air temperature and mean annual precipitation charts for the Greenland Ice Sheet. It is shown that melting of surface snow may occur at elevations of about 1,300 m. in north Greenland and up to 2,700 m. in south Greenland. The warming trend in the Arctic, as indicated by increases in mean annual air temperature, may have occurred to a lesser extent on the ice sheet than at sea-level coastal stations. Annual accumulation of precipitation is two or three times as great at 2,700 m. on the west side of the ice sheet as at the crest. South of lat. 66° N., precipitation may be about twice as great on the east side of the crest as on the west side.

Observations have been made in one of several deep holes drilled in Salmon Glacier in the course of mining development. Surveys, particularly of the displacement of a 481.5 m. length of pipe in this hole over a 94 day period, show movement diminishing downward from a maximum value of 0.225 m./day at the surface, through a slightly lower value at mid depth to 45 per cent of this value at the bottom of the pipe. By extrapolation movement on the glacier floor, 490 m. below the surface, is believed to be about 44 per cent of the surface rate. The data closely approximate Nye’s (1952) theoretical formula for laminar flow:

in which u0=78 m./yr., α=2°00′, n=2.8 and K=1.25×10−4. Maximum shear stress at the glacier floor is calculated to be about 1.42 bars.

Nye’s theory of the equilibrium profile of two-dimensional ice caps is modified to include longitudinal stress and creep rate effects. A more generalized law for the sliding velocity of a glacier over its bed is introduced into the analysis in order to permit the inclusion of these additional complications. It is found that in the case of small ice caps (of the order of 30 km. in width), it is important to include the longitudinal stress. A somewhat “flatter” profile than that calculated by Nye is obtained. For ice sheets of the dimensions of the Greenland or Antarctic Ice Sheets, the additional stress causes essentially no modification in Nye’s theory. Nye’s theory also has been extended to include an isostatic sinking under the weight of the ice of the bedrock below an ice cap.

Two small plateau ice caps in Arctic Norway are described and the amounts by which their areas have diminished during the past sixty years are assessed.

Some generally accepted views on joints in rocks, particularly exfoliation joints, are summarized. Lewis’ pressure release hypothesis is assessed in relation thereto. An additional hypothesis is suggested whereby the existing stress system in rocks due to the removal of overburden which would favour exfoliation, would be augmented by freezing of the saturated rock when the ice retreats, so triggering this type of extension joint.

The density of glacier ice containing a given amount of air can be computed if it is assumed that both ice and air are subjected to a pressure due to the weight of overlying material. In this way it is possible to deduce the form that a curve of density versus depth should have for ice of a constant air content. Reasons for the divergence of observed depth-density profiles from those predicted by this theory are discussed, in particular the effect of the plastic-viscous behaviour of ice, which results in an air pressure differing from the hydrostatic pressure of the ice above. The empirical power-law relation between depth and density is discussed in the light of this theory, and is also used to derive relations for useful parameters characterizing the densification process such as rate of subsidence and rate of densification in terms of the depth, accumulation, and the constants entering the power law.

The author agrees with Nye’s correction of two errors in a previous paper; but disagrees with his other objections. Evidence is put forward for the significance of a second approximation in the theoretical equation for the profile of a glacier; for instance, it explains why bulges of increased thickness travel down glacier faster than the ice. Features of the front of the Glacier de Saint-Sorlin are reported. An attempt is made to explain crevasse formation in glaciers and the upturning of blue bands at the foot of an ice fall.

A simple technique for measuring the pressure in individual bubbles of gas in glaciers is described. By this technique, bubble pressures in twenty-six west Greenland icebergs were measured. The bubbles were for the most part tubular in shape and oriented parallel, lending a fibrous and sometimes stratified appearance to the ice. Various suggestions are offered for the formation of these bubbles. Most bubbles had a pressure of 4–5 atmospheres, and pressures as high as 20 atmospheres were recorded. In closely adjacent bubbles differences of 2–5 atmospheres were often measured, which indicated diffusion tightness and lack of plasticity in the ice. When the ice surface melts, the bubbles expand at the cost of water extrusion. The various factors contributing to the maintenance of vertical walls characteristic of tabular bergs are discussed.

A new mechanism is described which explains the formation of moraines in the ablation areas of cold ice sheets. The mechanism involves the freezing of water onto the bottom surface of an ice sheet. This water comes from regions of the bottom surface where the combination of the geothermal heat and the heat produced by the sliding of ice over the bed is sufficient to melt ice. A number of criticisms are made of the shear hypothesis, which has been advanced to explain moraines occurring on Baffin Island and near Thule, Greenland. It is concluded that this older hypothesis may be inadequate to account for these moraines.

Although in theory the mechanism proposed in this paper undoubtedly will lead to the formation of moraines, the existing field data are insufficient to prove conclusively that actual moraines have originated by means of this mechanism.