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5 th Int. Workshop on Ice Caves (IWIC – V) Barzio (LC), Valsassina, Grigna and Milano, September 16 – 23, 2012 Volume of Abstracts ROLE OF SUBGLACIAL CAVES IN THE EVOLUTION OF GLACIER IN THE SNOUT AREA: TWO EXAMPLES ON THE FORNI GLACIER (VALTELLINA, I) AND MORTERATSCH GLACIER (CH) Tognini P. 1 1 Gruppo Grotte Milano CAI-SEM, Progetto Speleologia Glaciale, Via Santuario inferiore, 33/D- 23890 Barzago (Italy) (paolatognini@iol.it) After an advance in the early 80‟s, during the last 30 years all alpine glaciers are reacting to the recent growing of summer medium temperature and to poor snow falls with huge ice mass losses (with conspicuous reduction in volume and retreating of the glacier snout). Ice volume reduction goes together with changing in morphology, strain distribution and subsequent jointing. Constant monitoring and observations through time of the glacial caves point out as recent glacier changing are affecting also on the evolution of endoglacial caves systems and on the formation of contact caves. It is in fact well demonstrated that glacial caves strictly depend on the distribution of strain through the ice mass and on the water flow entering the caves: every change in one of these factors causes a change in the morphology of caves. On the other hand, the existence of glacial caves vice versa has a control on the evolution of the glaciers themselves. Expeditions on the largest glaciers all over the world allowed researchers to have an idea about the often spectacular morphologies glacial caves may display, but the smaller and relatively modest alpine glaciers offer us the opportunity to study continuously and systematically, over years, the evolution of these caves and to relate it with the evolution of the glaciers. Some examples of what is happening on Forni Glacier (Valfurva, Northern Italy) and on Morteratsch Glacier (Southern Switzerland) show the contribution cavers and speleologists can give with the simple and cheap methods of surface and cave survey, and photographic documentation they generally use in karst caves, without any expensive or complicate scientific instruments. On these two big glaciers it has been observed, from 2000 on, the way the evolution of very large contact caves is leading to the collapse of large areas at the snout during the last few years. The recent hot summer seasons enhanced ablation, enlarging subglacial discharge, together with sublimation processes due to air flow, thus creating contact caves much larger than in the past. This causes the snout stability to be compromised: thanks to the breakdown of large glacial galleries, at the snout huge ice masses are suddenly lost, together with a considerable reduction in length. The collapse of huge subglacial caves thus dramatically changes the morphology at the snout in a minute. 23
5 th Int. Workshop on Ice Caves (IWIC – V) Barzio (LC), Valsassina, Grigna and Milano, September 16 – 23, 2012 Volume of Abstracts The formation of huge contact caves as a prelude to dramatic breaking down and subsequent rapid evolution of the snout has been reported also on other alpine glaciers, such as the Scalino Glacier and Vedretta di Fellaria (both in Valmalenco, Northern Italy) or Gorner Glacier (Southern Switzerland). It therefore evident that contact glacial caves at the snout play a significant role in the evolution of the snout itself, thus being responsible for rapid and spectacular retreats: information given by the study of endo-and subglacial caves may thus help in forecasting glacier evolution in the very next future. GLACIAL CAVES OF THE BELLINGSHAUSEN DOME AND ADJACENT AREAS, KING GEORGE ISLAND, SOUTH SHETLAND ISLANDS, ANTARCTICA Mavlyudov B.R. 1 1 Institute of geography RAS, Staromonetny 29, Moscow, 119017, Russia Researches during summer seasons of 2007-2012 at Bellingshausen Dome have shown presence of glacial caves of 4 types: 1) usual; 2) the buried ice canyons; 3) in a shadow of rocky ledges; 4) marine. Usual glacial caves meet within the limits of glaciers of Island very seldom as here conditions for their formation very often are not observed (not present crevasses and there is no internal drainage or on the contrary many crevasses and there is no sufficient concentration of water streams for cavities origin). Therefore moulins here are not usually formed, but it is possible to meet glacial caves at the places of water outputs on a surface. All observed caves were englacial. Such caves have been met in the western part of the Dome and outside of the Dome near to its northern boundary. Separately stay cave which is formed under nunatak in northern part of a glacial dome which has been generated by melt water which got warm at their current on a rocky surface of nunatak up to 6°С. Length of the investigated cavity was about 70 m. The buried ice canyons are enough widely widespread and basically they are formed where the concentrated stream of melt water from the Dome flows along a moraine surrounding the Dome on perimeter. Permanent lowering of ice surface conducts to occurrence of the new ice canyons which are settling down further from boundary of glacier. The canyons abandoned by water are closed by snow, ice and moraine sediments forming glacial caves. There are canyons from several meters up to 15 m depth in southern, western and northern parts of the Dome. All founded moulins was connected with the buried canyons. Cavities in a shadow of rocky ledges are formed apparently everywhere in places where 24
Page 2 and 3: IWIC - V 5 th INTERNATIONAL WORKSHO
Page 4: President 5 th Int. Workshop on Ice
Page 7 and 8: 5 th Int. Workshop on Ice Caves (IW
Page 13 and 14: Dear Participants, we are very plea
Page 46: POSTER PRESENTATIONS
Page 61: 5 th Int. Workshop on Ice Caves (IW

Volume of Abstracts - Università degli Studi di Milano

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