Volume of Abstracts - Università degli Studi di Milano

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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 movement of a glacier is existed. However only caves at glacier boundary are accessible to research. Similar caves have been found out in southern and east parts of a glacial dome, and also on outlet the glaciers located to the north and northeast from a glacial dome. The caves length change from 10 to 30 m. Marine caves can be formed in sea wave-cut zone on the base of crevasse. The cavity represents a vaulted hall about 20 m in diameter and height up to 5 m. Formation of a cavity occurred by roof collapse with subsequent melting and carrying out of ice fragments by sea water. Analysis of available data shows that channels inside ice participate in drainage from the glacier but part of this drainage consist smaller part of common drainage from glacial dome. Climate warming can lead to increasing of internal glacier drainage and climate cooling can lead to reducing of internal glacier drainage. A NEW REGISTER FOR THE GLACIAL CAVES Ferrario A. 1 1 Gruppo Gruppo Grotte CAI Saronno, Progetto Speleologia Glaciale (aiaweie@hotmail.it) Explorations in glacial caves have been accomplished for many years, but a definitive method for their storage in a register has not yet been developed . The fact that these caves are inside moving glacial masses greatly complicates the methodologies for the creation of a register of them. In fact, they constantly shift and change over time, creating, developing and dying within a few years. But the possibility of identify these caves in space and time is of paramount importance to better understand their evolution and the correlation between them and the health of glaciers, being notoriously undergoing a strong reduction in recent years. The “Progetto Speleologia Glaciale” is developing a method of classification of glacial caves for the creation of a register of alpine glacial caves. The experience started in 2009 is demonstrating to be functional for the proposed aims, allowing us to follow year to year the evolution of each cave and then to study the mode of evolution. If applied to all the glaciers where glacial karst can be observed, this method makes it possible to obtain detailed knowledge of this phenomenon, in most cases not considered in classic glaciological studies. 25
5 th Int. Workshop on Ice Caves (IWIC – V) Barzio (LC), Valsassina, Grigna and Milano, September 16 – 23, 2012 Volume of Abstracts EVIDENCE OF A SUBGLACIAL LAKE IN A CONTACT CAVE ON THE FORNI GLACIER (VALTELLINA, I) Tognini P. 1 1 Gruppo Grotte Milano CAI-SEM, Progetto Speleologia Glaciale, Via Santuario inferiore, 33/D- 23890 Barzago (Italy);(paolatognini@iol.it) The Forni Glacier (Valfurva, Northern Italy) is the longest glacier in the Italian Alps: since 1995 a group of speleologists has been monitoring and studying its glacial caves over years. In 2009 it was therefore possible to observe the formation of a subglacial lake inside a cave. In the Eastern portion of the glacier in 2007 a contact cave was observed being created, fed by an alloctonous run off from the overhanging rock walls. The cave got larger and larger and in August 2009 a small lake was spotted inside, at the very end of a large subglacial contact gallery: soon after a breakdown caused two large parallel galleries to merge in one, creating an enormous chamber, where a large lake was formed on the bedrock. The existence of subglacial lakes on the glaciers bedrock is well established and confirmed by many field evidences, but they have rarely been directly observed: as far as we know, endo-and subglacial lakes have never been reported in Italian glaciers (and very few in the world), so that the lake below the Forni Glacier is the first evidence of a subglacial water basin. Unfortunately, the period during which it was possible to study the lake has been very short: contemporary to the formation of the huge chamber with the lake at its bottom, on the surface the opening of sets of circular crevasses was observed, as a prelude of a very next collapse: this happened in October of the same year, causing the almost total closure of the cave, although the lake was probably still there. In summer 2010 only a crevassed depression was left: both cave and subglacial lake had disappeared Thanks to the very rapid breakdown of the cave, it is probable that also the disappear of the lake should have been fast and sudden, presumably causing a water flow of GLOF (Glacial Lake Outburst Flow) type. The flow poured its waters into a surface contact lake down-flow, which, in its turn, was formed in 2006 and disappeared in 2010, because of the opening of a contact cave on the bottom (unfortunately, it was not possible to explore this cave because it was filled with big mud covered ice blocks). This chain of facts shows that the existence of large subglacial caves played a fundamental role in the glacier evolution, together with subglacial water circulation. The danger due to subglacial lakes is also evident: the pressure wave created by the sudden outburst after the destruction of the subglacial lake might be responsible for the opening of the cave that 26
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

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