Measurement of geometry, motion, and mass balance from Variegated Glacier, Alaska portray conditions in this surge-type glacier close to the mid-point of its 20 year surge cycle. Comparison of longitudinal profiles of ice depth, surface slope, and surface speed indicate that the motion occurs largely by internal deformation assuming the ice deforms according to the experimental law of Glen. Surface speed is not noticeably affected by local surface slope on the scale of the ice thickness or smaller, but correlates well with slope determined on a longitudinal averaging scale about one order of magnitude larger than the ice depth. The rate of motion on Variegated Glacier agrees well with rates on non-surge type temperate glaciers which have similar depth and slope. Although the (low regime at the time of the measurements is apparently typical of temperate glaciers, a large discrepancy between the balance flux needed for steady state and the actual flux is indicative of a rapidly changing surface elevation profile and internal stress distribution.

Radiative transfer theory is formulated to permit a meaningful definition of emissivity for bulk emitting media such as snow. The emissivity in the Rayleigh-Jeans approximation is then the microwave brightness temperature TB divided by an effective physical temperature 〈T〉. The 〈T〉 is an average of the physical temperature, T(z), weighted by a radiative transfer function ƒ(z). Similarly,

where e(z) is the local emittance. An approximate ƒ(z) is used to determine analytically the effects of various absorption coefficients, of scattering coefficients that vary with depth, and of the seasonal variation of T(z). It is shown that a mean emissivity, which is equal to the mean annual TB divided by the mean annual surface temperature Tm, is a useful quantity for comparing theory and observations. Snow-crystal size measurements, r(z), at seven locations in Greenland and Antarctica are used to determine the Mie/Rayleigh scattering coefficient γs(z) and to calculate the mean emissivities. The observed mean emissivities are determined by a which is the average of 12 monthly Nimbus-5 (1.55 cm) microwave observations, and the Tm measured at the same locations. The calculated emissivities are about one-half of the observed values. The assumption that each snow crystal is an independent and equally effective scatterer, and the use of an approximation to ƒ(z), tend to over-estimate the effect of scattering. Therefore, a parameter multiplying γs(z) is used. The emissivities calculated with a single value of this empirical parameter for all seven locations agree well with the observed emissivities, showing that the microwave emissivity variations of dry polar urn can be characterised as a function of the crystal sizes. One optical depth corresponds to a typical fini depth of 5 m, but significant radiation emanates from up to 30 m. Since r(z) depends on the snow accumulation rate A and Tm. the sensitivity of the emissivity to changes in Tm or A are estimated using this semi-empirical theory. The results show that a one degree change or uncertainty in Tm is approximately equivalent to a 10% change in A, and that such a change will affect the emissivity by 0.003 to 0.014 or the TB by about 0.6 K to 3 K, depending on the location.

A radio-echo sounder has been built with which both the amplitude and phase of radio echoes can be measured. In experiments with this instrument at the Devon Island ice cap, in the Canadian Northern Territories, precise amplitude and phase measurements have been made upon radio echoes from the bed of the ice cap. If these measurements are repeated after a number of years, the results, considered in conjunction with snow accumulation and compaction data, will be interpretable as a long-term change in the thickness of the ice cap. Wave dislocations and bend points have been observed in radio echoes reflected from the bed, It is suggested that amplitude and phase measurements from a network of sites may be synthesized in order to explore the geometry of the reflecting surface on a fine scale.

Ice samples representing at least some twenty years' accumulation, have been collected from a crevasse wall at 3 200 m (Glacier du Mont de Lans, Massif de l'Oisans), with a view to studying the behaviour of soluble and insoluble impurities in temperate ice. The stratification of the ice from the surface to 2 m and the disappearance of this stratification below 2 m are attributed to a variation in the glacier regime on both sides of the equilibrium line, rather than to a variation in the conditions of deposit of solid debris on the glacier surface, the strata do not necessarily correspond to an annual accumulation. Mineralogical analysis of the solid particles has allowed us to demonstrate two kinds of deposit: that consisting of the local Alpine material (hornblende) and that consisting of a mixture of local material and red sand of Saharan origin (anatase). A study of the distribution of major cations (Na, K, Mg, Ca) along a profile has revealed the existence of a process of leaching which follows an exponential law to a first approximation. The leaching produces a rapid evolution in the chemical properties of the ice compared with those of the original precipitation.

The retreat of glaciers since 1927 in Cordillera Blanca has produced dangerous lakes at the front of many glaciers. All the known data, most of them unpublished, are reviewed. The known aluviones are listed, and those of Chavin, Quebrada Los Cedros and Artesoncocha described in full. In these three cases a breach in the front moraine came from big ice falls into the lake. The protective devices made on the outlets are described, as well as the effects of the big earthquake on 31 May 1970. In the case of Laguna Parón, which keeps its level thanks to infiltrations, the fluctuations of the discharge of the springs as related to the level of the lake from 1955 to 1969 are reported. The projects for lowering the level of Laguna Parón and for emptying Safuna Alta are described. The latter partially emptied in fact by piping after the earthquake, allowing a final solution.

In front of Laguna Parón there is a huge moraine which turns through 90° in the middle of the valley and with a narrow covered glacier on the top. It has been studied by electrical exploration, and using the displacements of 43 marked boulders on the glacier. Assuming a uniform balance on the glacier tongue and semi-elliptical cross-sections, it has been possible to estimate this balance and the glacier thickness. A great amount of the measured velocity comes from the creep of the moraine itself, which seems 10 be a kind of rock glacier, probably without interstitial ire. It must have taken all the Holocene to be formed. During its complex history a proglacial lake must have formed at some time, the rupture of which explains the crooked form.

We explain how preliminary results concerning the internal constitution of the big push moraine at Safuna were obtained in 1967. Cross-sections which were obtained later through electrical and seismic exploration and arduous borings are given. Under the lake Safuna Alta there exists a layer of dead ice which is probably a remnant from an old glacier advance and over which the active glacier slides, but this dead ice does not extend into the push moraine. Since 1950 Safuna Alta has formed, the glacier tongue has lowered by 0.8 m per year on average, and the big push moraine has moved and settled.

The annual balance on the glacier tongue was measured in 1968. It increases by 3.9 m of ice per 100 m in altitude. The discharge of ice near the lake and the annual balance further up-valley allow an estimate of the mean annual balance in the accumulation zone (between 4850 and 6020 m) at 2.30 m of water per year. Until now no annual precipitation higher than 1 m/year had been measured in Cordillera Blanca, but this Cordillera includes many meso-climates.

Eight successive moraines are found at Safuna. They are tentatively correlated with the eight existing between Huaraz and Laguna Llaca. Clapperton's (1972) “group 4” was not formed during the 20th, but during the 17th century. His “group 3” is not from A.D. 1750-1800, but is rather 5 000 to 7 000 years old, according to the offset of Cordillera Blanca great fault.

Several theories exist on the origin of kettle-holes in pro-glacial outwash deposits. The most widely accepted origin involves the melting of buried ice. The author carried out some experiments in which ice blocks were placed on or in outwash sediments in a tank in order to determine which mechanisms of ice melt would be most likely to give rise to kettle-hole features. The largest kettle-holes were produced by the melting of buried ice blocks; smaller transient depressions were formed from ice blocks melting in streams of flowing water; while, rather than depressions, ridges resembling pingos and moraines were created by ice blocks melting on a dry or saturated gravel surface.

The Laurentide and Fennoscandian ice sheets had three major glaciation maxima during the Last Ice Age. All data from the southern margins of the ice sheets indicate that these maxima, as well as minor fluctuations, were synchronous. The same synchroneity is supposed to apply also for correlations between fluctuations on the north and south margins, which reveal a continuously southward displacement of the distribution of glaciation during the Last Ice Age. This southward displacement explains the saw-tooth pattern of 18O records from deep-sea cores in which the first glaciation maximum is under-represented due to its distribution more towards the north. The synchroneity is consistent with a global climatic control of the stadial/interstadial changes and with the recorded global eustatic changes. The southward displacement of glaciation seems to be a general rule also applicable to earlier Pleistocene glaciations.

During a field survey in High Semyen, northern Ethiopia, two moraine complexes were mapped, the lower one extending down to around 3 750 m. Glacial morphology is best developed in the north-western and western quadrants. Moraines are deeply weathered and carry abundant vegetation. For Mounts Badda, Cilalo, Cacca and Enguolo in southern Ethiopia, possible moraines are inferred from air photographs; there are indications for more pronounced glaciation in the western quadrant, and moraines seem to extend further down than in High Semyen. Highest moraines at Mount Elgon in northern Kenya/ Uganda were found to below 3 600 m. Major moraine complexes in the mountains of Ethiopia and East Africa suggest some spatial correlation in elevation and appearance, but absolute dates are absent.

A microtoming and replicating technique has been developed for examining the micro-structure of sea ice optically and by scanning electron microscope. This dual observation method is useful for studying the grain and sub-grain structure of sea ice, the nature of the brine pockets, and the precipitation pattern of the salt crystals at low temperatures.

Evidence from aerial photographs, maps, and field checks indicates that 319 glaciers lie in cirques of the Rocky Mountains, south of the United States-Canadian border. On a subcontinental scale, the distribution of glaciers is highly clustered, with larger and denser clusters located in the northern Rocky Mountains. Lesser concentrations of small glaciers occur in the southern Rocky Mountains. The total area of glaciers in the Rocky Mountains of the U.S.A. is 78.9 km2.

An analysis is made of the disturbance in conductive heat flow caused by drilling a bore hole in ice in which there is a vertical temperature gradient. The model used is that of a perfectly insulating hole placed in a linear temperature gradient; it is shown that the temperature measured at the bottom of the hole deviates from its value before drilling by an amount of order —0.6aU where a is the bore-holt radius and U is the temperature gradient. The deviation takes effect in a few hours. The error is typically between 0.005 and 0.1 deg and is therefore significant only where very high accuracy is required. It should not be present in temperate glaciers, nor where the thermometer is properly frozen in, nor if temperatures are measured at the bore-hole walls far above the bottom.

The study indicates that no significant difference in snow densities is found when using either the CRREL tube or the ILTS box cutters. However, inexperienced workers tend to overestimate snow densities in light snow and depth hoar by 6 and 4% respectively.