Some examples of gypsum karsts and the more important gyspum caves in Spain

Spain possesses some of the most important examples of gypsum karst in Europe, in terms of the extent and variety of the gypsiferous outcrops. These are divided into gypsum belonging to the Triassic, Palaeogene and Neogene epochs, each of which displays different lithological and structural aspects. Some of Spain�s most significant gypsum karsts, from the speleological standpoint, are described, and these share a common characteristic of all supporting the development of large caves. Reference is made to the geomorphology, hydrogeology and hydrochemistry of the gypsum karsts of Sorbas, Vallada and Gobantes-Meliones, which provide significant examples of intrastratal karst, speleogenesis by saline groundwater mixing and the influence of carbonate strata, respectively. Finally, brief geomorphological and speleogenetic descriptions of the more significant gypsum caves in Spain are given, together with a list of the longest and deepest gypsum caves in Spain

Lava tubes of the Rohio lava field (Rapa Nui, Chile): exploration and scientific interest

Rapa Nui has one of the world\u2019s highest density of lava tubes. Apart some sporadic visits in the 1960s and 70s speleologists have become interested in this island only recently (see speleological references below). The present paper presents the exploration and the research carried out in the framework of three international speleological expeditions to Rapa Nui (2005, 2007, 2008) organized by the Sociedad de Ciencias Espeleologica Alfonso Antxia from Bilbao (Spain)

Geostatistical spatiotemporal analysis of air temperature as an aid to delineating thermal stability zones in a potential show cave: Implications for environmental management

Air temperature in several galleries of the Covadura System (Sorbas Gypsum Karst, Almería) was measured at monthly intervals over a period of 1 year. The spatial temperature distribution for each month was modeled in a geostatistical framework. The mean trend of the air temperature and the difference between each experimental temperature measurement and this trend were calculated over space and time. Both the trend and residual component were characterized using a geostatistical space–time model. A large spatial trend of the air temperature was found due to the orientation of galleries within the cave system and as a function of the distance from the main cave entrance. Kriging was used for the spatial estimation of the time covariance of the residuals. This enabled the delimitation of the cave into three zones of varying environmental risk in the event of being opened to visits by the public, according to the degree of stability of air temperature over space and time. The influence of human presence on the spatial temperature distribution was assessed using data collected during a year (2000/2001) in pilot galleries opened to the public. An average visit corresponding to August was selected comprising 16 people over a period of 53 min. This average visit influenced the spatial temperature pattern at distances of more than 90 m from the cave entrance, according to the geostatistical model adopted. Within this zone the mean thermal increment generated by human presence was estimated to be 0.26 °C. The spatiotemporal mathematical model of the cave air temperature has been revealed as a useful tool for the environmental management of show caves

Dissolution of Gypsum from field observations

The paper reports the results of field measurements of gypsum dissolution in various countries (Ukraine, Spain, Italy and others) and in different environments (river waters, precipitation, vadose zone, unconfined aquifer, perched cave lakes, ephemeral streams in caves, confined aquifer, cave air)

Environmental control for determining human impact and permanent visitor capacity in a potential show cave before tourist use

Cave temperature monitoring was carried out in the Cueva del Agua de Iznalloz, Granada, Spain, a cave that has great tourist potential and which has been maintained under natural conditions for over 30 years. The cave temperature under natural conditions was used to identify possible anthropogenic influences, in order to distinguish these from the variations directly related to natural changes. In particular, the relative influence of external weather conditions, thermal modification caused by visitors and the subsequent thermal recovery of the cave were identified. In addition, controlled experiments investigated the effect of two large-scale visits (980 and 2088 visitors day−1) to the cave interior, before any tourist activities in the cave were undertaken. Correlation and spectral analyses of time series were used to determine the thermal behaviour of the cave over time. The effect of both mass visits on the air temperature in the interior of the cave was very rapid (2.5 min). The maximum perturbation of air temperature within the cave during the two experiments was after 30 and 70 min. The memory effect for temperature whilst the cave was open to the public was estimated to be 5–6 h, whilst the response to external meteorological changes exceeded one week. A permanent visitor capacity of 53 people ensures that the natural cave temperature can be regained within 4–5 h. The cave can only support small groups of visitors, not the massive visits characteristic of show caves

Allogenic contact caves in Central East Sardinia (Italy): their speleogenesis and evolution

Several important cave systems in Central East Sardinia develop, at least partially, along the contact between the granite or phyllite basement rocks and the covering fractured Middle Jurassic sediments. The latter are composed of layers of clays, marls, conglomerates and sands of variable thickness (generally some metres) followed by sandy dolostones, becoming increasingly carbonatic moving upwards in the sequence. These karst systems are fed by allogenic streams with flow rates ranging from a couple to some thousand of L s-1. Parts of these vadose passages are sometimes developed in the insoluble basement rocks for some metres. In the summer of 2010 cavers of the Centro Speleologico Cagliaritano have discovered a new cave, Gutturu \u2018e Murgulav\uf2 (Baunei), that hosts some passages entirely excavated in granitic rocks. The typical morphology of all these caves is characterised by very large and rather low chambers, which floor is masked by important graviclastic deposits. Locally the Palaeozoic bedrock is exposed along the underground streams. Speleogenesis of these cave systems is very much relied upon weathering of the basement rocks and their successive erosion by flood waters, rather than on dissolution of the carbonate rocks. Mineralogical analyses of the weathering products at the contact between Palaeozoic rocks and Mesozoic sediments have revealed the presence of montmorillonite, kaolinite, chlorite and illite, typical weathering products of granitic rocks. Dissolution, however, plays an important role in the first stages of speleogenesis, dissolving the carbonate cement in the basal sandy dolostone beds, thus leaving loose sands that can readily be eroded by running waters. Once a critical dimension in void is reached, cave formation occurs very rapidly, leading to huge chambers in some thousands of years