In parallel the CGI promoted studies on single glaciers, with geophysical, topographical, glaciological and hydrological surveys, and organized eight national glaciological conferences since 1970.

Although the Committee activity mainly concerns the Italian glaciers, many members of the CGI participated or promoted glaciological investigations in other mountain chains and in the polar areas.

The results of the surveys together with many studies and monographs on glaciology have been published in the Bollettino del CGI since 1914, renamed Geografia Fisica e Dinamica Quaternaria since 1978. A synthesis of the glaciological surveys has also been reported in La rivista del Club Alpino Italiano since a few years. The data and conference proceedings are published in the volumes of the Archivi del CGI. Finally the results of the annual surveys, duly selected and simplified, are reported in the volumes Fluctuations of Glaciers edited by the World Glacier Monitoring Service (UNESCO).

Glaciers are formed by the gradual transformation of snow into firn and ice, in those areas where the snow that annually accumulates on the ground exceeds the one lost by melting or by otherprocesses and where the topographical conditions are suitable.

Ice behaves as a solid capable of being deformed under its own weight. Because of the force of gravity, through basal sliding and inner deformation, the ice flows downhill, at a speed of meters -hundreds of metersper year. Crevasses areopenfractures, generally not deeper than 30 m,formed under tension produced by friction ordifferential movementofglaciers.

There are approximately eight hundred glaciers in the Italian Alps according to the last census in 1989. There is also a small glacier on the Gran Sasso, in the Central Apennines. The Italian glaciers cover an area of about 500 km² and are mainly concentrated in the highest massifs of the Western and Central Alps. The widest continuous glacial complex is the one of Mt. Adamello (18 km²), while the biggest valley glacier is Forni glacier (13 km²). However a great part of the Italian glaciers is represented by small cirque and valley glaciers.

From the second half of the XIX^th century a phase of marked contraction has been taking place causing the reduction of the surface of the Italian glaciers by around 40%. The equilibrium line altitude has raised by approximately 100 m. Many small glaciers disappeared, while the widest onessplit sometimes into smaller units, receding their fronts up to 1-2 km. This phase of glacial retreat, is recognized in nearly all the mountain glaciers of the Earth, and is attributed to the ongoing climatic warming.

The Alpine glaciers, mostly characterized by an ice temperature close to that ofmelting, are highly sensitiveto climatic changes thatcontrol their mass balance and their size variations. By deciphering the traces of glacier activity left in the environment (moraines, erosion landforms, vegetation boundaries, etc.) it is possible to reconstruct the changes in glacier extentand behaviour and therefore to extract information on the climate variations inthe past. The glacier ice itself contains information on the physical and chemical characteristics of the atmosphere from which the original snow was derived.

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Glaciers constitute an important water resource, suitable to be used for agricultural, civil and industrial purposes. Many hydroelectric systems are fed, at least in part, withglacial meltwater. Therefore glaciers contribute significantly to the production of hydroelectric energy, which in Italy represents approximately 20% of the whole electric power produced.

Glaciers are moreover a characteristic element of the Alpine landscape, and constitute an attraction and a resource for hiking, mountaineering, and winter and summer skiing.

Due to the increasing number of tourists and settlements high up in the mountains, glaciers can also constitute an element of risk. Falls of ice and avalanches, glacier outbursts due to sudden emptying of ice dammed lakes or ofwater trapped in cavities, together with the instability of recently deglaciated areas (rock falls, debris flows, etc.) can risk the visitors' safety and that of buildings, ski runs and tourist tracks. Harmful events connected with the glacial dynamics have recently taken place in Italy.

To assess a glacier “state of health”, a measure of its mass balance is carried out by comparing the mass gained from snow precipitation and avalanche accumulation with the one lost as a result of the melting process andice falls to the front. By means of geophysical surveying it is possible to reconstruct the thickness of the glacier, the inner structure and the bedrock morphology. The annual measurement of the glacial front positions,by means of different topographical techniques, allowsa reconstruction of the fluctuations of the glaciers, reflecting the climatic and environmental changes.

Bibliographical, cartographic and iconographical surveys enable us to gather data on the frontal positionsassumed by the glaciers in the recent past.

The study of ice cores by means of physical and chemical analyses allows the reconstruction of the recent history of climate and atmosphere,also through the studyof the gases contained in the air bubbles trapped inside the ice.

The geologicalsurvey and the photointerpretation allows us to map the glacial sediments and the erosional forms that, dated by means of various techniques (lichenometry, dendrochronology, ¹⁴C dating of buried soils and organic remains) supply the history of the glacial variations.

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Realization: Maurizio Santilli, 2001

Dipartimento di Scienze della Terra, Sezione di Geologia e Paleontologia, Università di Milano, Via Mangiagalli 34, 20133 Milano

maurizio.santilli@unimi.it

Update: 18 July 2006