A regression model calibrated on 23 cirques from the Sangre de Cristo Mountains, south-central Colorado, suggests that local-scale climatic controls interact with geologic materials to explain intramountain variation to cirque development. Topoclimatic effects maximize cirque development on ridges that project well above the Pleistocene glaciation limit, and in positions that minimize total radiation receipt. If an optimum topoclimate coincides with densely jointed (erosible) bedrock materials, cirque development will be at a maximum. However, cirque development can be deceptively poor in situations where a favorable topoclimate coincides with massive (sparsely jointed) bedrock materials. The interaction between local-scale climatic–geologic controls subsumes their independent effects. Significant correlation between cirque development and an individual process control may not emerge due to complications produced by one or more other controls.

Equipment has been designed and tested for ground-based and airborne sounding of temperate glaciers. The transmitter is a free-running pulse generator that uses avalanche-mode transistor breakdown to create high-voltage pulses. The transmit and receive antennas are resistively loaded dipoles; for the airborne system, a twin-lead transmit element and a three-layer coaxial receive element are used on the inboard end of the respective antennas. The sounders are broadband systems; oscilloscopes are used for receivers. The oscilloscope trace is recorded photographically in the ground-based systems. A sampling oscilloscope is used in the airborne system—the sampling process strobes the waveform to audio frequencies so that it can be recorded on magnetic tape. Echoes have been obtained from ice depths of 550 m using the airborne system and about 1 000 m using the ground-based system.

To provide engineers with a better tool, we have developed a program for avalanche computation. After a brief description of the mathematical model and the assumptions, we describe influence of physical and numerical parameters, which allows a better understanding of the physical phenomenon which we call an avalanche. The satisfactory agreement between computations and observations allows us to assume that the model is well founded; further experiments will allow us to improve this simulation tool.

Neoglacial to historic and recent fluctuations of the firn field and one glacier on Popocatépetl, Mexico, include advance prior to 1519 to possible mid-Neoglaciation stadial position on gentle, north flanks at 4 150 m, then retreat up-valley to 4 335 m by 1906, and to 4 435 m by 1920 at 7 m/year. After volcanic eruptions and melting to about 4 800 m in 1921, growth of firn field and advance of a thin ice lobe before 1949 to 4 573 m by 1950, then retreat in next eight years at about 34 m/year, re-advance of the firn edge as an ice bulge to about 4 700 m by 1968, and as a thick double-lobed glacier to about 4 600 m by 1978 and 1979. A 37 year crevasse study shows continuous active firn-field movement on the north-west side of the cone.

An electromagnetic stress-wave generator which was developed to study shock waves in snow and ice is described. This system works on the principle of generating large electrical currents to produce highly transient loads on the test specimen. In its present configuration, the generator can produce pressures ranging from a few kilopascals to as large as 104 kPa and load frequencies as, high as 150 kHz. The system has been found to have high repeatability and has good turn-round time.

The Nimbus-6 satellite carries the Scanning Microwave Spectrometer experiment (SCAMS) which continuously maps the Earth’s surface at two frequencies (22.235 and 31.65 GHz) and at six angles besides nadir. Cluster analysis was applied to these observations to determine the influence of various geophysical parameters on the radiometric brightness temperatures.

Characteristic microwave signatures for a variety of terrain were obtained by this method; discrete clusters were distinguished for sea ice (with sub-classes for ice age and fractional ice cover) and firn (with accumulation-rate sub-classes). The availability of the angular data greatly facilitated separate determinations of the extent of continuous sea ice and mixtures of sea ice and water.

The stable isotopes oxygen-18 and deuterium in snow samples collected in four mountain regions (the South American Andes, the Central Asian Hindu Kush, the Himalaya, and Mounts Kenya and Kilimanjaro in Africa) have been measured. The altitude effect in fresh snow precipitation and in the snow-pack was determined for δ180 as being within the range —0.6‰ to about — 1.0‰ per 100 m of elevation, but this can be altered or even inverted by secondary factors. These factors are connected with conditions of snow-fall and post-depositional changes in the snow, which are strongly dependent on the topography of the sampled mountain slope and on climatic conditions. All these effects are discussed.

The design and operating characteristics are presented for a visible and near-infrared scanning photometer which can measure incident and reflected spectral irradiance from 400 nm to 2 450 nm. The instrument is designed to record over 98% of the solar radiation incident upon and reflected from the Earth’s surface using a turret-type cosine collector and a circular variable interference filter. The apparatus has been tested successfully on Arctic sea ice at temperatures down to –20°C. It is self-contained and easily portable, and its mass is less than 16 kg. Some preliminary results are presented.

A layer of moraine within the Antarctic ice sheet has been detected in the course of airborne radar ice soundings. The moraine was injected at the margin of the ice and can serve as a tracer to pick out a particle path within the ice. When combined with surface measurements, the ability to trace particle paths should allow detailed modelling of the dynamic behaviour in limited areas.

Contemporary processes of moraine development at the margins of polar glaciers encompass a wide range of subtly different mechanisms. Two types of “controlled” moraine evolution, applicable to hummocks and transverse moraine ridges, are identified from Wright Lower Glacier and Webb Glacier, southern Victoria Land, Antarctica. Type 1 moraine complexes involve a relatively abundant supply of supraglacial debris, the development of transverse thrust blocks in the ablation-zone ice and the subsequent re-arrangement of ablation debris in ablation cusps and on inactive thrust blocks. Relict landform suites, apparently formed in this manner, reveal large coarse-grained hummocks inset behind moraine ridge remnants.

Type 2 moraines may develop where the supply of supraglacial debris is meagre but the growth of ablation cusps concentrates primarily englacial debris into small irregular hummocks. The gravel component of this debris is usually of finer texture than for type 1 deposits, reflecting abrasion/attrition effects of prior englacial transportation. Transverse moraine ridges may or may not be associated with type 2 hummocks, depending on local variations of ice motion, ice decay, and debris supply.

Creep tests were performed in torsion and torsion–compression on polycrystalline ice at temperatures near the melting point. Syntectonic recrystallization occurs at strains of the order of 2–3%, leading to a rapid increase in strain-rate. It is shown that the increase of creep-rate during tertiary creep arises from the development of fabrics favouring the glide on basal planes but also from the softening processes associated with recrystallization. The c-axis fabric of recrystallized ice developed in simple shear consists of two-maxima, one at the pole of the permanent shear plane and the other between the normal of the second plane of maximum shearing stress and the principal direction of compression. In torsion–compression, a three- or four-maximum fabric is formed according to the intensity of different components of the stress tensor. The maxima are clustered around the principal direction of compression. Processes of fabric formation are discussed. The experimentally developed fabrics are probably produced by the strain-induced recrystallization, for which the driving force is provided by differences in stored plastic strain energy. However the degree of preferred orientation of ice c-axes must be a function of the total strain when syntectonic recrystallization becomes less important. In this case, fabrics are principally formed by plastic flow and a steady state is obtained for very high strains.

The Orville Coast area of the Antarctic Peninsula was extensively glacierized in the past. Striations, polished rock surfaces, and erratics on nunatak summits indicate that this area was covered by a broad regional ice sheet whose grounded ice margin was on the continental shelf, in the present-day Ronne Ice Shelf area. If the glacial history of Antarctica has been controlled by eustatic sea-level changes, the destruction of this ice sheet would have been contemporaneous with that of the Ross Sea ice sheet due to the world-wide rise of eustatic sea-level at the end of the Wisconsin glaciation.

Biaxial compression tests on glacier ice with bubbles revealed that elongated air bubbles were developed with long axes in the direction of free expansion. The elongated bubbles were not only derived from spherical bubbles but also created by the healing of cracks that were developed during compression. Formation of elongated bubbles and foliations in natural glacier ice are discussed here in the light of results obtained experimentally.

Some features around the perimeter of the Balgesvarri plateau ice cap are described. Sorted stone circles were found beneath a slowly retreating ice margin, the basal ice in this area appears to be below the pressure-melting point. No absolute dating of features was possible but a relative chronology is suggested.

Triaxial testing of frozen saturated Ottawa sand under confined compression was carried out under hydrostatic pressures varying between 0.1 and 75 MPa at a temperature of -10°C and strain-rate 7.7×10-5 s-1. Yield and failure stresses increased with increasing hydrostatic pressures up to about 40 MPa, beyond which the stresses dropped. The results are analysed according to the Mohr-Coulomb failure criterion and compared with past results in the literature.

Drumlin till has often been described as clay-rich. Drumlins in Ontario are composed of sandy till. Additional examples from north-eastern North America show that sandy till is common in drumlins.

It is suggested that the widely accepted association between drumlins and clay till was fostered by the use of such terms as “boulder clay” and “glacial clay”. Also, because till in drumlins may be finer than other glacial materials in such areas as the Appalachian region, a loose and exaggerated description of such material as being clay-rich arose. More careful description of drumlin till is advocated. It is suggested that grain-size distribution of till may have had a role in drumlin formation.

Recent investigations have shown that various factors may affect the shear strength of glacial till and that these factors may be involved in the drumlin-forming process. The presence of frozen till in the deforming zone, variation in pore-water pressure in the till, and the occurrence of random patches of dense stony-till texture have been considered. The occurrence of dense stony till may relate to the dilatancy hypothesis and can be considered a likely drumlin-forming factor within the region of critical stress levels. The up-glacier stress level now appears to be the more important, and to provide a sharper division between drumlin-forming and non-drumlin-forming conditions.

Total snow depth is determined by measuring the time of flight of an ultrasonic wave packet emitted from a sonic transmitter above the snow surface and reflected from the snow surface back to the receiver/transmitter system. The light-weight system is battery powered (operating time without battery change at least 8 months) and can be fixed to any post above the snow surface. The absolute precision is better than ±0.03 m. Data and commands are transmitted by a single two-wire system up to several kilometres.