They are a vital source of information about the glaciations that covered significant areas of Poland in the Pleistocene. They intrigue not only scientists, but also geotourists. So why do glacial erratics so frequently end up vandalized?

Fennoscandinavian erratics found in the glacial deposits till and in the glaciofluvial sediments within the main limit of the Odra glacier lobe (NW Poland and NE Germany), have been examined in two fractions: of 4-10 mm and 2060 mm. The most numerous in the fraction of 4-10 mm are: crystalline rocks (Cr; 35-40%) originating in the Protero zoic Baltic Shield as well as Lower Palaeozoic limestones (LPL; 35-40%) - from the sedimentary sheet covering the Proterozoic Baltic Shield in the area of central Baltic Sea. Percentage of sandstones (S) amounts to 10-15%. The re maining rock types (several percent each) are: Palaeozoic shales (PS), the outcrops of which are localized in Scania (Skane) and on Bornholm, Cretaceous limestones (CL) and flintstones (F) originating from the western part of the southern Baltic Sea as well as quartz (Q), milk quartz (MQ) and isolated grains of Devonian dolomites (DD). From the analysis of indicator erratics, which was carried out in the 20-60 mm fraction, it appears that mainly the outcrops localized in Smaland (e.g. red and grey Viixjo granites, Paskallavik porphyries or Tessini and Kalmarsund sandstones) as well as in Scania (Hoor and Hardeberga sandstones) and Region Blekinge-Bornholm (e.g. Karlshamn and Halen granites as well as Nexo and Bavnodde sandstones) had been subjected to the glacial plucking. Theoretical boulder centres (TBC, German: TGZ das Theoretische Geschiebezentrum, Uittig 1958), which were calculated for 23 samples, are localized mostly in a small area in Smiiland, between 15°E-16°E and 56.5°N-58.5°N. Apart from indicator erratics the statistical ones are numerous, that are first of all grey and red Lower Palaeozoic limestones with their outcrops localized at the bottom of the central Baltic Sea. Taking into account the TBC values of indicator erratics as well as high percentage of statistical erratics it can be pronounced that the section of central and western Baltic Sea as well as the one of south-eastern Sweden had been subjected to the heaviest glacial plucking by that part of the Pleistocene ice-sheet which reached the studied area during the Pomeranian Phase.

The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics.

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