Proposition de géomorphosite glaciaire sur le versant Nord-Est du volcan Etna (Sicile). – Le mont Etna est le plus grand volcan actif du continent européen (environ 3 300 mètres d’altitude). Au cours du dernier maximum glaciaire (25 000 ÷ 14 000 ans BP), l’Etna culminait environ 700 mètres plus haut que de nos jours. En considérant le fait que les autres montagnes de l’Apennin ont été couvertes par des glaciers au cours du Pléistocène Supérieur, plusieurs auteurs ont proposé une possible couverture glaciaire de l’Etna au cours de la dernière glaciation. Il a aussi été supposé que, à cette époque, la limite des neiges permanentes se tenait sur l’Etna à 2 500 mètres. Les roches volcaniques antérieures au dernier maximum glaciaire affleurent à Punta Lucia sur le versant Nord-Ouest, et à Serra delle Concazze sur le versant Nord-Est. Sur la haute côte nord-est de l’Etna il y a une petite vallée qui a un profil transversal en forme de “U”, typique des vallées glaciaires. La vallée est longue 170 mètres et a une largeur moyenne de 15 mètres et une profondeur de 7 mètres. En hiver, cette vallée est souvent recouverte de neige, et dans les cas d’événements pyroclastiques, elle est souvent remplie par des dépôts épais de cendres et de lapilli. À cause de l'intensité du couvert forestier, ainsi que des coulées de lave et des dépôts pyroclastiques qui cachent les rochers des côtés de l’Etna, aucun dépôt morainique n’a été trouvé jusqu’à présent. Une telle découverte pourrait confirmer l’origine glaciaire de cette vallée.
Mount Etna is the largest active volcano of Europe and the highest mountain (about 3,330 m a.s.l.) of peninsular and insular Italy; moreover, during the Last Glacial Maximum (LGM, 25,000 ÷ 14,000 years BP) it was some hundreds meters higher than today. Since other mountains of the Apennines were covered by glaciers during the Upper Pleistocene, several authors hypothesized that a glacial cover could have been also present on Mount Etna during the LGM, being the estimated limit of perpetual snow around 2,500 m a.s.l. at that time and latitude. We have carried out a morphological survey in a portion of the volcanic edifice where rocks older than the LGM outcrop. This portion includes Punta Lucia, on the NW slope, and Serra delle Concazze, on the NE slope. Along the upper part of the northeastern slope of Etna we have found a small valley, about 170 m long, 15 m wide and 7 m deep, characterized by a clear U-shaped section, that we interpreted to be of glacial origin. The search for moraine deposits that could be ascribed to the activity of the hypothesized glacier was unsuccessful so far and is also complicated by the presence of vegetation and recent lava and tephra deposits covering the volcano flanks. We are aware that this valley should be considered as a possible geomorphosite to guarantee its preservation and further study.
Proposal of a geomorphosite for a small glacial valley on the northeastern flank of the Mount Etna volcano (Sicily).
IMPOSA, Sebastiano;
2012-01-01
Abstract
Mount Etna is the largest active volcano of Europe and the highest mountain (about 3,330 m a.s.l.) of peninsular and insular Italy; moreover, during the Last Glacial Maximum (LGM, 25,000 ÷ 14,000 years BP) it was some hundreds meters higher than today. Since other mountains of the Apennines were covered by glaciers during the Upper Pleistocene, several authors hypothesized that a glacial cover could have been also present on Mount Etna during the LGM, being the estimated limit of perpetual snow around 2,500 m a.s.l. at that time and latitude. We have carried out a morphological survey in a portion of the volcanic edifice where rocks older than the LGM outcrop. This portion includes Punta Lucia, on the NW slope, and Serra delle Concazze, on the NE slope. Along the upper part of the northeastern slope of Etna we have found a small valley, about 170 m long, 15 m wide and 7 m deep, characterized by a clear U-shaped section, that we interpreted to be of glacial origin. The search for moraine deposits that could be ascribed to the activity of the hypothesized glacier was unsuccessful so far and is also complicated by the presence of vegetation and recent lava and tephra deposits covering the volcano flanks. We are aware that this valley should be considered as a possible geomorphosite to guarantee its preservation and further study.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.