Constant dripping wears the stone

The waters of the Ceira River crossing a very hard quartzitic crest of Ordovician age (Buçaco-Penedos de Góis syncline) in Central Portugal, near the city of Lousã. The outcrop section comprises one of the most complete Ordovician records in Portugal, from the Lower Ordovician (Armorican Quartzite) with an important fossil content (Cruziana, brachiopods, trilobites, bivalves) to the Upper Ordovician with glacial tills portraiting the Hirnantian glaciation.