Three types of glacier margin are found along the edge of the Greenland ice sheet near Thule: ice cliffs, ramps and ice-cored moraines. Where the glacier margin is perpendicular to prevailing katabatic winds, drifting snow accumulates along it in stagnant wind-drill ice wedges. Upward flow of active ice behind these wedges causes ice originally near the base of the glacier to rise to the surface. Where this basal ice is free of debris, a gently sloping ramp develops. However, where the basal ice contains sufficient debris, a layer of till accumulates on the glacier surface. Ice beneath the till is insulated and a debris-capped ice ridge or ice-cored moraine forms, Ice cliffs occur where the ice-sheet margin is parallel to prevailing winds and is thus swept clear of drifting snow. Although the ice sheet in the Thule area appears to have had a negative mass balance for many years, all three types of glacier margin are believed to be equilibrium forms that can develop and persist on a glacier with a balanced mass budget.

Foliation in wind-drift ice wedges generally dips down-glacier but foliation in active ice dips up-glacier. It is inferred that foliation in the wedges was once sedimentary stratification that has been tipped upward and locally overturned.

Methods used in measuring the mass balance of the Devon Island ice cap are described. The use of dyes and melt trays is recommended in the superimposed-ice and firn zones of sub-polar glaciers. The north-west part of the ice cap was studied in most detail and has had a slightly negative net balance for the period 1961-66. An inverse relationship between mean net balance (bn) and elevation of the equilibrium line in the north-west part of the ice cap indicates that the mean net balance there would be zero with an equilibrium line at 920 m (±80 m) elevation. Accumulation on the ice cap is greatest in the south-east but the measurements suggest that the mean net balance there is similar to the mean net balance on the rest of the ice cap. It is concluded that the present accumulation pattern must have existed for several hundreds, and possibly thousands of years. A study of firn stratigraphy and of variations in the elevation of the firn and equilibrium lines indicates that between 1961 and 1966 only 1962 had a more negative mean net balance than the average value for the period 1934-60. During the same 26 year period the net balance at 1 787 m elevation has varied, but summer conditions do not appear to have changed significantly.

An air-photograph inventory of the present glacierization of areas of east Baffin Island adjoining Home Bay and Okoa Bay is described. Ice fields characterize the broad mountain summits of the former while the latter is an area of cirque glaciers. The extent of glacierization is statistically related to various topographic parameters. It is found that there is a 4: 1 ratio between Home Bay and Okoa Bay in the area of ice as a percent of the land area above 600 m a.s.l. Trend-surface analyses are made of the distribution of snow-banks and of cirques (empty and with ice bodies) in the two areas. The orientation of the cirques and of the ice-field glaciers in Home Bay is also examined. 39% of empty cirques in Okoa Bay face south, whereas those with existing glaciers are restricted to orientations with azimuths between 310°-145°. Neither glacier length nor the observable recession in the Home Bay area show any significant difference with regard to; aspect.

Consideration of climatic parameters (snowfall and degree days) and synoptic-climatological results provide no reason for the strong contrast between the two areas. Cool, cloudy summer conditions are associated with easterly flow components that should affect both areas. A possible model for the inception of the mountain ice fields of Home Bay c. 2000-4000 years ago is outlined and it is suggested that differential lag effects between the ice bodies in the two areas may be responsible for some of the observed difference. The many paradoxical relationships between glacierization. topography and climate in these areas, and the rather negative results, emphasize the dangers of facile palaeoclimatic interpretations.

“Fox Glacier”, Yukon Territory, has a history of surging and is at present in a quiescent period. In 1968 a gravity survey was carried out over the glacier, in order to find ice depths. The results indicate the glacier is thin with a maximum depth of 88 m.

Measurements were made of the vertical electric field Strength around snow cornices on Bridger Ridge (2 590 m a.s.l.) in the Bridger Range, South-western Montana. The fields were considerably enhanced, owing to the exposed position of the cornices, but were nevertheless appreciably lower than those shown by Latham and Saunders (1970[b]) to be necessary in order to provide significant additional bonding when ice crystals collide with an ice surface. However, measurements made on Bridger Ridge and neighbouring Bangtail Ridge showed that the charges carried on snow crystals saltating over the surface of cornices were close to their limiting values.

Rough calculations indicated that pressure melting is unlikely to be of importance in the development of snow cornices formed from granular crystals, that frictional melting is probably significant only at fairly low temperatures and moderately high wind velocities, and that strong electrostatic forces between highly charged snow crystals saltating over the surface of a cornice may be sufficient to provide bonding where the crystal velocities are comparatively low.

The top surface of an accurately aligned ice crystal is melted by an aluminum surface and then frozen to a warm “Lucite” plate ant! tapped free. Etch-pit development shows that the dislocation density on the resulting surface is similar to die bulk dislocation density determined by X-ray topographic methods.

Thickness variations above an ice fall in the terminal tongue of Coleman Glacier on Mt Baker, Washington, have been quite small (±5 m) in contrast to the rapid expansion and shrinkage of the tongue itself during the last 20 years. The tongue has not responded as actively to recent, larger thickness changes above the ice fall as it did during its period of most active expansion between 1954 and 1956. There is no apparent relationship between the glacier thickness and the type of flow in the terminal tongue.

Recovery of the Muldrow Glacier in the area below the lower Muldrow ice fall is progressing at a rapid rate. About one-third of the lost ice thickness at the base of the ice fall has been replaced during the 10 years since the surge. The ice velocity in this region is apparently quite rapid, but quickly decreases down-stream and is barely detectable at McGonagall Pass, 6.5 km from the base of the ice fall. Muldrow Glacier still offers an excellent opportunity to study the recovery from a surge, and the flow of a normal wave into stagnant ice.

Finger-rafting, similar to that reported in sea ice, is common in thin (2-15 mm) new ice on Lake Superior. It is produced by wind traction alone; neither wave action nor brine is necessary for its initiation or propagation. Fingers have been observed to progress at rates of 0.5-5 cm/s.