Development of the unique landforms in the zone of weathering gypsum-anhydrite rocks at Pisky (Shchyrka river valley, Dnister basin)

 The exceptional site with actively weathering anhydrite rocks at Pisky quarry near Lviv shows a peculiar relief created by the process of anhydrite hydration (transformation of this mineral into secondary gypsum), and associated volume increase and swelling of the rocks. The ongoing deformation leads to the formation of specific landforms at the bottom of the quarry, such as pressure ridges, hydration domes and hydration (swelling) caves. The latter forms represent a very rare type of caves, known only in a few places on Earth. For nearly ten years the evolution of this relief has been systematically documented and analysed by taking multiple photos and by the method of benchmarks. The site offers a rare opportunity to study the process of development of the hydration domes and caves also in the future, until the whole anhydrite transforms into gypsum.