Apulia Region (Southern Italy) presents a very high percentage of soluble (carbonate) outcropping rocks. Karst phenomena are therefore widespread, and mark the territory with typical landforms and features. Among these, the Vora Bosco swallow hole, located in Salento, is one of the two sites in the region that allow man to move within a cave system, eventually reaching the groundwater. Interception of the water table, at a depth of – 60 m below the ground (altitude of the cave entrance: 64 m a.s.l.), makes Vora Bosco one of the most important caves to direct study the complex hydrogeological dynamics in the Apulian karst. The underground environment is characterized by very narrow passages, and the system is almost entirely developed inside calcarenitic formations (Plio/Pleistocene – Miocene), with only the few last meters within the Cretaceous limestones. The Vora Bosco plan, realized by speleological surveys, draws a predominant E-W elongation direction of the cave system. Numerous monitoring actions have been started since October 2017 inside the karst system and in the surrounding superficial areas, in order to collect geological, hydrogeological and biological data from both surface and subsoil. Among the informations collected so far (internal and external meteorological data, water level, temperature and electrical conductivity, petrological and structural data) the processing and analysis of the cave climate values has revealed extremely interesting. Karst scientists typically consider the cave environment quite stable, with a temperature about equal to the mean external temperature value at the access of the cave. However, in at least two cases, during February 2018, the Vora Bosco temperature fell down very quickly. The three HOBO sensors, installed along the cave pathway to register temperature and humidity data, with a pace of one measure per hour, detected significant and sudden temperature values decreases (about 10 °C in 24 h), through the whole cave system. In addition, such a decrease in temperature is accompanied by a correspondent lowering in the groundwater temperature, and by a significant rise in the groundwater level, following intense rainfall. This behavior could be explained considering that Vora Bosco is a shallow karst system that, since it develops prevailingly within porous calcarenites, rapidly drains the rainfall towards the deepest sectors of the cave. The cold water remains inside the rock mass pores, thus influencing the HOBO temperature records. In addition, the turbulent flux of rainwater, which disappears within the subsoil crossing the cave entrance, produces a cold spray, adding its effect to the previous one. Analysis of these events, and of the related micro-climate changes, is still going on, aimed at quantifying the time required by the Vora Bosco karst system to return to steady state conditions (that is, to the situation present before the rainstorm).
Micro-climatic aspects at the karst system of Vora Bosco (Salento, Southern Italy)
LISO I. S.;PARISE M.
2019-01-01
Abstract
Apulia Region (Southern Italy) presents a very high percentage of soluble (carbonate) outcropping rocks. Karst phenomena are therefore widespread, and mark the territory with typical landforms and features. Among these, the Vora Bosco swallow hole, located in Salento, is one of the two sites in the region that allow man to move within a cave system, eventually reaching the groundwater. Interception of the water table, at a depth of – 60 m below the ground (altitude of the cave entrance: 64 m a.s.l.), makes Vora Bosco one of the most important caves to direct study the complex hydrogeological dynamics in the Apulian karst. The underground environment is characterized by very narrow passages, and the system is almost entirely developed inside calcarenitic formations (Plio/Pleistocene – Miocene), with only the few last meters within the Cretaceous limestones. The Vora Bosco plan, realized by speleological surveys, draws a predominant E-W elongation direction of the cave system. Numerous monitoring actions have been started since October 2017 inside the karst system and in the surrounding superficial areas, in order to collect geological, hydrogeological and biological data from both surface and subsoil. Among the informations collected so far (internal and external meteorological data, water level, temperature and electrical conductivity, petrological and structural data) the processing and analysis of the cave climate values has revealed extremely interesting. Karst scientists typically consider the cave environment quite stable, with a temperature about equal to the mean external temperature value at the access of the cave. However, in at least two cases, during February 2018, the Vora Bosco temperature fell down very quickly. The three HOBO sensors, installed along the cave pathway to register temperature and humidity data, with a pace of one measure per hour, detected significant and sudden temperature values decreases (about 10 °C in 24 h), through the whole cave system. In addition, such a decrease in temperature is accompanied by a correspondent lowering in the groundwater temperature, and by a significant rise in the groundwater level, following intense rainfall. This behavior could be explained considering that Vora Bosco is a shallow karst system that, since it develops prevailingly within porous calcarenites, rapidly drains the rainfall towards the deepest sectors of the cave. The cold water remains inside the rock mass pores, thus influencing the HOBO temperature records. In addition, the turbulent flux of rainwater, which disappears within the subsoil crossing the cave entrance, produces a cold spray, adding its effect to the previous one. Analysis of these events, and of the related micro-climate changes, is still going on, aimed at quantifying the time required by the Vora Bosco karst system to return to steady state conditions (that is, to the situation present before the rainstorm).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
