Can the Hranice Abyss, the Deepest Underwater Cave in the World, Really Reach 1 km Depth? A Comment on the Paper by Klanica et al. (2020)

Based on shallow geophysical data, Klanica et al. (2020, ) argued that the deepest undewater cave in the world, the Hranice Abyss (HA) had formed by epigenic karstification related to mid-Miocene opening of similar to 1 km deep Carpathian Foredeep (CF) and, hence, could be similar to 1 km deep. However, the CF subsided and the abyss was uplifted due to post mid-Miocene faulting with at least 460 m vertical offset, which makes the depth estimate of Klanica et al. (2020, ) invalid. It remains unclear under which geological circumstances the HA, if formed by epigenic karstification, could be backfilled with water column reaching similar to 400 m of height.