The Unicorn Cave, Southern Harz Mountains, Germany: From known passages to unknown extensions with the help of geophysical surveys

摘要

In soluble rocks (limestone, dolomite, anhydrite, gypsum,...), fissures and bedding partings can be enlarged with time by both physical and chemical dissolution of the host rock With time, larger cavities evolve, and a network of cave passages can evolve. lithe enlarged cave voids are not too deep under the surface, geophysical measurements can be used to detect, identify and trace these karst structures, e.g.: (i) gravity revealing air- and sediment-filled cave voids through negative Bouguer anomalies, (ii) electrical resistivity imaging (ERI) mapping different infillings of cavities either as high resistivities from air-filled voids or dry soft sediments, or low resistivities from saturated sediments, and (iii) groundwater flow through electrical potential differences (SP) arising from dislocated ionic charges from the walls of the underground flow paths.