During the Middle Proterozoic orogenic period, the earlier structures of the Finnish bedrock underwent such intense deformation that also the later, differentiated, crustal movements, which were epeirogenic in nature, took place mainly along the deep fractures produced at this time. Recent seismicity, manifested by the latest deformation phase, is likewise associated with these crustal zones of weakness of ancient origin. An apparent, seismogenic, cause-and-effect relation is to be found in both the internal and external tectonics of the Fennoscandian Shield.