The reinterpretation of Claudius Ptolemy’s Germania Magna by Sven Mildner

DOI https://dx.doi.org/10.23689/fidgeo-5907
Sven Mildner https://orcid.org/0009-0005-8248-4866

In his draft on “The Reinterpretation of Claudius Ptolemy’s Germania Magna – with the help of computer-aided image distortion of a medieval map representation of Donnus Nicolaus Germanus – and considerations on the postglacial geodynamics of Europe”, the author describes his assumption that Germania Magna was subject to a more comprehensive landscape transformation than previously assumed, due to the postglacial land uplift in the late Holocene, or due to a possible reactivation of the Caledonian Deformation Front (CDF) in the course of a late activity phase of the Alpine orogeny and the associated tectonic activities in the upper earth crust.*) These are possibly connected with hitherto unassigned or incorrectly dated fracture events of larger scale, which could also have led to stronger earthquakes in Europe and which may even have been handed down to us from the Middle Ages[1]. According to the interpretation, the area of Germania Magna described by Ptolemy corresponds in its latitudinal extent approximately to the area of the Federal Republic of Germany, i.e. without including parts of present-day Poland, as previously described by other interpretations. Large parts of the Central European Depression, however, were probably covered by a shelf sea – at least temporarily. Denmark, or Jutland, had no connection to the mainland, according to the representation of Germania Magna and according to this interpretation.

Which geological processes led to a possible regression of the Oceanus Germanicus is not the primary subject of this interpretation, but the author suspects several factors here, which have already been outlined in the publication and which could form a common cause for this. According to the latest considerations, however, the reactivation of the CDF in the course of a late activity phase of the Alpine orogeny (i.e. in more recent times) seems to be a possible main cause. During this event, tectonic forces caused Avalonia to be thrust eastward onto the Baltic continental plate, possibly depressing it (potentially a beginning subduction, but temporally limited and regionally restricted to the eastern part of the Avalonian continental plate) – with the consequence that the relative sea level (RSL) at the North German coast fell and that land areas in the Oceanus Germanicus suddenly lay below sea level. Both Vesuvius and Etna in Italy, as well as the volcanoes on Iceland, had several strong eruptions in the mentioned periods (e.g. 79 AD the eruption of Vesuvius, which destroyed Pompeii), which suggests a general high level of geoactivity in Europe that could have led to stresses in the lithosphere and triggered or intensified continental drift. In this context, maybe the (renewed) uplift of the island of Rügen, which represents the rest of the tip of the Avalonian plate eroded away and protrudes from the sea, could also have taken place.

The publication initially assumed post-glacial land uplift to be the main cause of a regression, which, in conjunction with the end of a warm period (the Roman climatic optimum), could consequently have led to a falling relative sea level (RSL) on the North German coast. Previously, even less water may have been bound in glacial ice than after the Little Ice Age in the Late Middle Ages – i.e. in the last five hundred years up to almost the present day. The work of Olav Liestøl was used in this consideration, who in the late 1950s evaluated the course of the firn line of western Norwegian glaciers over a period of about 10,000 years (Glaciers of the present day. In: Olaf Holtedahl Geology of Norway. (=Norges Geologiske Undersökelse, Nr. 208). Oslo, 1960.).

Also according to W. Dansgaard et al. (1969), Schönwiese (1995) and Roth (2018), and not least the word etymology of Greenland as “Greenland”[2], already indicate that the average temperature at the time of Ptolemy and during the Middle Ages was higher over longer periods than in the last five hundred years, and that Greenland was initially perceived as green and thus as fertile when it was named. Erik the Red is considered one of the first Vikings to settle Greenland at that time. His life is reported in Nordic sagas, here especially in the Eiríks saga rauða.

So it is likely that sea peoples, as ancestors and relatives of the Vikings, developed on the island groups in the northern Germania Magna (cf. also Varangians), or the Vikings themselves. It is probable that these seafaring tribes migrated from the mainland to the islands in the Oceanus Germanicus, not least due to the expansion pressure in the Roman Empire – or, since they lost their original settlement areas due to the transgression. For the same reason, the Völkerwanderung could also have started, if not warlike conflicts were the main motive here.

It can be assumed that at that time many fortifications and early water castles, or even entire cities (cf. The Saga of Vineta) were built in the shallow water, on islands and on peninsulas (cf. also the article on Viking ring forteresses or generally on ramparts), or that the inhabitants lived on protected marshland islands (Halligen), or that these buildings were later silted up or destroyed by flooding events. Taking into account the present interpretation, the author also finds it quite conceivable that historically recorded storm floods in the North Sea and Baltic Sea can in fact be attributed to earthquake-induced tsunamis (cf. Mandränke).

However, the present interpretation may also provide a better explanation for archaeological ship finds[3] in Mecklenburg-Western Pomerania, which can initially be interpreted as grave goods, but which could then also have been sunken ships that were covered by sand and silt as a result of the silting-up process.

*) Supplement of 31.03.2024, Sven Mildner:

possible uplift of the Avalonian continental plate by the mountain building process and the reactivation of the Caledonian Deformation Zone (CDF) (or the formation of a high mountain range in the Oceanus Germanicus)

The onset of Avalonian thrusting may have also led to a stronger crustal thickening in the region of the Netherlands and the North German Wadden Sea. This, in turn, could have resulted in a tilting of the Avalonian continental plate or the surface topography (isostasy). The cause of this may have been a north-south directed force in the context of the Alpine orogeny, which could have led to an uplift of the North German coastal area and the Central European Basin, and perhaps also to a further uplift of the Erzgebirge (Ore mountains) in recent geological times, or generally to an uplift of the low mountain ranges along the Thuringian-Franconian-Vogtland Slate Mountains, further along the Main river to the Rhenish Slate Mountains, including the Taunus and Hunsrück. This could also have caused a northwest tilt of the Avalonian continental plate, also because a (limited) obduction onto Baltica could not have occurred equally at all sutures, since Avalonia was overlain by Laurentia in the west and thus ultimately tilted for another reason. This is rather a collision of two continental plates and not the subduction of oceanic crust.

Please also refer to the work of Lyngsie, S.B. & Thybo, H.. (2007). A new tectonic model for the Laurentia−Avalonia−Baltica sutures in the North Sea: A case study along MONA LISA profile 3. Tectonophysics. 429. 201-227. 10.1016/j.tecto.2006.09.017., which shows that the continental crust of Baltica had already begun to fold in the study area (Caledonian foreland thrust belt), presumably as a prelude to the formation of an accretionary wedge in the Jutland area, with the possible further consequence of a northward displacement of the Sorgenfrei-Tornquist Zone due to the forces acting here.

A comparable event has taken place in the past, for example, to a greater extent in the collision of India with Eurasia (cf. Jiang, Feng & Chen, Xiaobin & Unsworth, Martyn & Cai, Juntao & Han, Bing & Wang, Lifeng & Dong, Zeyi & Tengfa, Cui & Zhan, Yan & Zhao, Guoze & Tang, Ji. (2022). Mechanism for the Uplift of Gongga Shan in the Southeastern Tibetan Plateau Constrained by 3D Magnetotelluric Data. Geophysical Research Letters. 49. 10.1029/2021GL097394.). In essence, this would represent the initial stage of mountain building, which may have been interrupted in the North German coast due to the wedging of three continental plates (Avalonia, Baltica, and Laurentia). Therefore, stronger forces would be required at this point to continue the process, which can already be traced here through the depiction of Germania Magna. Thus, the process of Alpine orogenesis may have shifted in our time from the Alps more towards Scandinavia, or significant uplift may now only take place there, depending on the activity of the Mid-Atlantic Ridge and the force exerted on Europe by the collision with the African continental plate.

Likewise, it could also be inferred that there are very likely phases of stronger and weaker activity, rather than a uniform mountain building process, and that there must have been very strong activity phases in between to bring about the necessary extent of landscape change (geomorphological change) (since this process has so far hardly been recognized as such in Northern Europe and has probably been relatively inconspicuous here since the beginning of modern geosciences).

It is also worth mentioning that the shortening of the continental crust in length obviously also goes hand in hand with its uplift, which leads to graben fractures in the hinterland. (cf. again Jiang, Feng & Chen, Xiaobin & Unsworth, Martyn & Cai, Juntao & Han, Bing & Wang, Lifeng & Dong, Zeyi & Tengfa, Cui & Zhan, Yan & Zhao, Guoze & Tang, Ji. (2022). Mechanism for the Uplift of Gongga Shan in the Southeastern Tibetan Plateau Constrained by 3D Magnetotelluric Data. Geophysical Research Letters. 49. 10.1029/2021GL097394.)

Thus, the Eger Graben may also have been more closely related to this process, or have been caused by earlier (perhaps even periodically occurring) events of the same nature. Likewise, however, it should also be considered whether the Elbe Valley Basin between Meißen and Dresden could ultimately be a result of such processes. In my opinion, the Germania Magna indicates that the area around the Elbe Sandstone Mountains and the Lusatian Mountains could have experienced geomorphological changes in the meantime. According to the description of the Germania Magna, the Erzgebirge was already present, but it is difficult to say whether it may not have experienced another uplift in recent geological times, which is related to the tectonic-induced regression of the Oceanus Germanicus, or a (further) subsidence of the Erzgebirge foreland, as a result of a beginning overthrust of the continental crust at the coast – and, as already indicated, with the associated shortening of the continental crust in the interior of the country – although, according to the previous view, such processes should essentially have taken place at a much earlier point in time. However, even after the relief of the crust by the decrease of the force effect (relaxation), graben structures could probably still form.

It is therefore quite conceivable that there is an even closer connection between the current uplift of Scandinavia and the Alpine orogeny than previously suspected and that the postglacial land uplift could therefore only be partly responsible for this. The comparatively rapid uplift of Scandinavia in modern times could then possibly be attributed to a folding of the continental crust.

The approach of Scandinavia to Central Europe has probably also led to the formation of the North Sea Central Graben, as a bulge of the continental crust (cf. Arfai, J., Franke, D., Lutz, R. et al. Rapid Quaternary subsidence in the northwestern German North Sea. Sci Rep 8, 11524 (2018). https://doi.org/10.1038/s41598-018-29638-6). Former land areas in the North Sea, such as Albionis pars, were probably thereby made part of this graben structure and have consequently fallen below the present sea level. In this context, there is perhaps also a closer relationship to the opening of the Upper Rhine Graben (cf. Mediterranean-Mjösen Zone). The area around the Rhenish Slate Mountains to the English Channel could have acted here as a pivot or anchor point (or as a support point) for a slight rotation, in which a change in the direction of the force took place, due to the solid structure in the subsurface, which only yielded to a limited extent.

[1] See Dr.-Ing. habil. G. Meier (1998). Historical earthquakes in the Erzgebirge, In: Sächsische Heimatblätter No. 20, https://www.dr-gmeier.de/pub/oa0003.pdf

[2] See Preiser-Kapeller, J. (2020). The Long Summer and the Little Ice Age: Climate, Pandemics, and the Transformation of the Old World, 500-1500 AD, ISBN 978-3854768890, also taking into account the etymology of Greenland as “Grünland” [Greenland].

[3] For example, so-called “Usedom Boat Graves” see BIERMANN, Felix. Usedomer Bootsgräber. Germania: Anzeiger der Römisch-Germanischen Kommission des Deutschen Archäologischen Instituts, 2004, 82nd edition, No. 1, pp. 159-176.

Draft publication Project website: https://www.germania-magna.de

Mildner, Sven. (2020). The reinterpretation of Claudius Ptolemy’s Germania Magna – with the aid of computer-assisted image distortion of a medieval map by Donnus Nicolaus Germanus – and considerations on the postglacial geodynamics of Europe. 10.23689/fidgeo-5907.

ISBN 979-8573568980

Project website: https://www.germania-magna.de

Note: This edition is an incomplete preliminary release from 2020, as cooperation with university research was unfortunately no longer possible due to political reasons in the course of the Corona crisis. Therefore, the manuscript could not be completed, the content could not be subjected to expert review, and it could not be elaborated into a more comprehensive work until today. The author had to postpone the project due to his civil and societal commitments, but still publishes this preliminary version so that the content can become part of scientific consideration.

The publication quality of the digital edition is unfortunately somewhat limited because the book pages had to be recovered from an already created file copy. As part of his civil engagement to preserve our democracy, combat fascism, and prevent the restriction of our basic rights, the author’s work computer with the original files was confiscated and unlawfully withheld until the day of publication of this draft edition.

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