Abstract
Spatial distribution of isobases of recent vertical crustal movements displayed by the map indicates certain predominant directions (lineaments). The directions coincide with main regional structural directions of the Alpine and Hercynian structural stage in Poland. The movements are concentrated along deeply seated discontinuities and weakness zones of the crust perpendicular to the main direction of tensional normal stress (NW-SE) or parallel to the direction of maximum shear stresses (WNW—ESE, NNE-SSW). The recent vertical crustal movements of Poland are mainly of taphrogenic or block-wave nature. Local halokinetic and orogenic (tangential) movements are also of some importance. Subsidence taking place in a broad meridional zone of the Polish Lowland peripheral to areas glaciated during the last Pleistocene ice stage seems to be at least partly related to glaciisostasy. The wave nature of the recent vertical movements of the earth's crust is confirmed by results of their harmonic analysis. The movements may be described as the net result of overlapping waves of different length and frequency. There are no data which would indicate that recent crustal movements in Poland are directly related to sea-floor spreading of the northern Atlantic Ocean, but it is admitted that this relationship is suggested by some indirect evidence.
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