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Abstract. — First is described the place of glaciers during Quaternary Era in these mountains. Then the author deals with the correlation between glacial areas and major karst landforms such as caves, underground conduits, canyons, poljés with alluvial cover... Minor karst land- forms are related with post-glacial and actual corrosion.

Abstract. — With the recent discovery (1980-81) of the big underground system "BU56" ( — 1 338 m), the hydrogeology of the karst of " St.Georges" begins to be better known. This system represents 30-35% of the subterranean hydrology, that is to say a 2 mЗ/s cube (specific flow = 66-70 l/s/km2) against 5,64 mЗ/s cube in the principal efflux (Illamina). During the year, we observe an hydrologie regime with 2 maxima (spring, autumn-winter) and 2 minima (summer, winter). The importance of the chambers and galleries is the result of several processes: corrosion, collapses and faults on paleozoic substratum (shales), mecanic erosion of the underground rivers. The specific dissolution is about 95-100 mm/ 1000 years with 15-20% for the superficial corrosion, 40-45% for the first part of the deep corrosion (0-50 m) and 40% for the deep corrosion.

Abstract. — The general conditions of karstic denudation in this area are recorded. Diabolskoto Irelo cave and lagodina canyon are described, with a reference to the problem of vertical und underground karst drainage.

Abstract. — The Pierre Chave spring wich give the Morge river, is an emergence of an important karst system (Jurassic link of the Ratz). We trie to determin its area of alimentation by geological and hydrody- namic studies and underground water tracing. In this limestone country where the geological structure cannot give an exact definition of this area and where the tertiary and quaternary recovery is very important, only the application of those different methods can give a good result and obtain the means to protect the spring.

Abstract. - The frame work of a research on Vercors and of the « Karst denudation » commission of the Speleology International Union, we took care to estimate the corrosion which is exerting on this massif under current bio-climatic conditions. Two complementary methods of approach had been used : physico-chemical analysis of water circulating in Karst and the method of calcareous thin slab. In order to determine the more precisely possible the work of corrosion in Vercors and to grasp seasonnal fluctuations, samplings and measures had been done regularly over a three-year period (from 1979 to 1981).

Abstract. — From intermittent observations and continuous measures taken during 21 months on the rock faces in the Combe de Laurichard (Briançonnian Alps), we have tried to approach the rockfall mechanism triggering the demolishing of walls and the development of screes in mountain environment about 3 000 meters high. The rapid falling of materials from fractured crystalline rock masses, allows rockfall inventory all the year round north and south facings. Temperature recorders set in various sites make it possible to situate the major peak of rockfall activity in spring, i.e. between april and june depending on aspect. As many authors, we emphasize the distinction between primary and secondary falls, which shows how important the topographic pattern is.