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The karst of Sorbas (SE Spain) is one of the most important gypsum areas worldwide. Its underground karst network comprises over 100 km of cave passages. Rounded smooth forms, condensation cupola and pendant-like features appear on the ceiling of the shallower passages as a result of gypsum dissolution by condensation water. Meanwhile, gypsum speleothems formed by capillarity, evaporation and aerosol deposition such as coralloids, gypsum crusts and rims are frequently observed closer to the passage floors. The role of condensation–dissolution mechanisms in the evolution of geomorphological features observed in the upper cave levels has been studied by means of long-term micro-erosion meter (MEM) measurements, direct collection and analysis of condensation waters, and micrometeorological monitoring. Monitoring of erosion at different heights on gypsum walls of the Cueva del Agua reveals that the gypsum surface retreated up to 0.033 mm yr− 1 in MEM stations located in the higher parts of the cave walls. The surface retreat was negligible at the lowest sites, suggesting higher dissolution rates close to the cave ceiling, where warmer and moister air flows. Monitoring of microclimatic parameters and direct measurements of condensation water were performed in the Covadura Cave system in order to estimate seasonal patterns of condensation. Direct measurements of condensation water dripping from a metal plate placed in the central part of the El Bosque Gallery of Covadura Cave indicate that condensation takes place mainly between July and November in coincidence with rainless periods. The estimated gypsum surface lowering due to this condensation water is 0.0026 mm yr− 1. Microclimatic monitoring in the same area shows differences in air temperature and humidity of the lower parts of the galleries (colder and drier) with respect to the cave ceiling (warmer and wetter). This thermal sedimentation controls the intensity of the condensation–evaporation mechanisms at different heights in the cave.

Montecchio cave (Grosseto province, Tuscany, Italy) opens at 320 m asl, in a small outcrop of Jurassic limestone ( Calcare Massiccio Fm.), close to the Albegna river. This area is characterised by the presence of several thermal springs and the outcropping of travertine deposits at different altitudes. The Montecchio cave, with passage length development of over 1700 m, is characterised by the presence of several sub-horizontal passages and many medium- and small-scale morphologies indicative of sulphuric acid speleogenesis (SAS). The thermal aquifer is intercepted at a depth of about 100 m below the entrance: the water temperature exceeds 30 °C and sulphate content is over 1300 mg l − 1 . The cave hosts large gypsum deposits from 40 to 100 m below the entrance that are by-products of the reaction between sulphuric acid and the carbonate host rock. The lower part of the cave hosts over 1 m thick calcite cave raft deposits, which are evidence of long-standing, probably thermal, water in an evaporative environment related to significant air currents. Sulphur isotopes of gypsum have negative δ 34 S values (from − 28.3 to − 24.2‰), typical of SAS. Calcite cave rafts and speleogenetic gypsum both yield young U/Th ages varying from 68.5 ka to 2 ka BP, indicating a rapid phase of dewatering followed by gypsum precipitation in aerate environment. This fast water table lowering is related to a rapid incision of the nearby Albegna river, and was followed by a 20–30 m fluctuation of the thermal water table, as recorded in the calcite raft deposits and gypsum crusts.