Abstract:
The rapid underground dissolution of gypsum, and the evolution of the gypsum karst in Lithuania and England, results in subsidence problems which can make construction difficult. The natural dissolution yields sulphate-rich groundwater of poor quality and the karst is susceptible to the rapid transmission of pollutants. In the north of Lithuania gypsum karst is developed in Devonian gypsum. Here the towns of Birai, Pasvalys and the surrounding countryside suffer subsidence and some buildings have been damaged. The majority of the potable water in these areas is derived from groundwater extracted from sandstone sequences that underlie the gypsum. In Lithuania conservation measures have been introduced to control agriculture and prevent pollution of the gypsum karst. These measures include environmentally-friendly farming, restrictions on land use and exclusion zones around subsidence hollows. In England subsidence caused by the dissolution of Permian gypsum has caused severe problems in the vicinity of the town of Ripen. Numerous buildings have been damaged and new sites are difficult to develop. Here formal planning regulations have recently been introduced to help to protect against the worst effects of subsidence resulting from gypsum dissolution. (C) 1999 Elsevier Science B.V. All rights reserved