Contenu du sommaire : Comptes rendus critiques

Abstract. — Like the near Roya-Bevera Valley, the demographic evolution of the Vesubie (South Alpes), in middle altitude (2700 feet) is characterised by a depopulation most accentued in the agricoltury villages then the villages with non agricoltury activities.

Abstracts. — Our experiments of spectrozonal stereophotogram- metry in the Western Alps are related to Spacelab program using a metric camera in the perspective of the first Spacelab flight aboard of NASA Space Shuttle, which will over fly the Alps between 4th and 11 th December 1980. We made aerial and ground photographs of Wallis mountains (Obergabelhorn, Blanc de Morning, Zinalrothorn close to Zinal) and of Dolomiti di Cortina d'Ampezzo (Tre Cime di Lavaredo) in Italy, using spectrozonal emulsions (Kodak S. 0 .410 or classical Ektachrome Infra-Red) and optical multichannels filters. These technics are compatible with European Space Agency and NASA specifications, owners respectively of Spacelab and Space Shuttle: final ground resolution better than 20 meters, with exposure speeds of 1/1000 second at the scale of 1/820.000 on the film, in spite of a ground motion of 7.755,75 meters per second. In that way, several elementary forms of alpine geomorphology (ind ice — or snow phenomena will be detectable on metric scenes of this first industrial survey from space.

Abstract. — The timing and duration of the meltseason has been objectively determined for five Mont-Blanc glaciers by defining critical minimum flow values of the glacial meltwaters. The smaller glaciers experienced far longer "meltseasons" than the larger glaciers, as annual melting extended more quickly to the more distant parts of the smaller basins. Significant correlations were found to exist between the surface area of each of the five glaciers and their mean meltwater discharge for each month ; interpolation from these relationships allowed the probable annual regime of meltwaters from the neighbouring, but unmonitored, Bossons Glacier, to be predicted. Measurements of sediment amounts removed by meltwaters from the Bossons Glacier suggest that the granite and schist bedrock is eroded at the rate of 600 to 900 mm per 1000 years. About 60 per cent of this amount appears to have been removed in suspension, compared with about 23 per cent as bedload and 1 per cent in solution, while about 16 per cent of the fluvioglacial debris eroded from the Bossons Glacier basin has been deposited to form a proglacial valley-train. Some problems involved in making estimates of rates of glacio-hydrological erosion are also discussed.