European Geologist Journal 48
The Geological Wall in Berlin – Over 120 years of teaching geology
by Ulrike Hörmann1, Angela Ehling2 and Klaus Reinhold2
1 Senate Department for the Environment, Transport and Climate Protection – Berlin Geological Survey
2 Federal Institute for Geosciences and Natural Resources (BGR), Berlin
Contact: angela.ehling@bgr.de
Abstract
In 1896 Eduard Zache, a school teacher and geologist in Berlin, planned and built a “Geological Wall“ to provide a geological understanding of landscapes and their stones to the people of the growing town of Berlin. He arranged 123 different rocks forming idealized strata sets and tectonic structures in a wall with a length of about 30 m and a height of average 2 m. The arrangements simulate geological formations in former Germany in a very detailed manner and they cover all geological periods. Thus, the strata sets of the Muschelkalk in Rüdersdorf near Berlin are pictured as well as the copper deposit of the Rammelsberg, along with folded Devonian strata in the Harz Mountains, the granite pluton of Lusatia, reef limestones, basaltic columns breaking through older rock strata and much more. The wall does not only show and illustrate features and the genesis of rocks, deposits and geological structures; it reflects the use of stones and raw materials at the end of the 19th century, too. Nowadays this Geological Wall still exists and is in use for teaching.
Introduction
The hundred-year old history of the Geological Wall does not fit to geological scales but is, nevertheless, an extraordinary geotope. Originally, the geological wall was an object for learning and teaching outdoors (Fig. 1), or as the builder, Eduard Zache, wrote: “A demonstration model to introduce the theory of the structure and the treasures of the Earth’s crust” (Zache, 1896).
Its original location was in the Humboldthain, a park in Berlin-Wedding directly next to the botanical school garden. Because of the growing city it was moved to the botanical garden in Berlin-Blankenfelde during 1912 to1914, today the Botanical Park (Wutzke & Liebram, 1999).
Figure 1: Teaching in front of the Geological Wall at the end of the 19th century (Engel et al., 1990).
Unlike collections of rocks, e.g. in museums or schools, the geological wall has created a combination of rocks and their natural distribution (Fig. 2). This makes it easier to understand geological structures and earth history. Therefore, geology is the central topic of the geological wall.
The wall is divided into 20 sections (A–U) illustrating geological systems, stratigraphic series, geological structures and tectonic events in the way they really appear in sites located in the former Germany. The ground rock controls the surface shape of the wall, and in its original location this continued into the region behind the wall for a 3-D-effect (today only to some extent).
Figure 2: A current view of the Geological Wall in the botanical garden in Berlin-Blankenfelde.
The geological wall contains even more information from the past and present. The construction of the wall at the end of the 19th century and the rocks used are closely linked to the history of Berlin. Furthermore, it has significance from a geohistorical point of view because it reflects the state of geological knowledge at the end of the 19th century. One example is the absence of Ordovician rocks because this system, although defined in 1879 by Charles Lapworth, was only recognised in the 20th century.
As far as mining is concerned, the wall has serious historic value because the stones often came from the then active mining districts and quarries, e.g. the Mansfeld copper slate district, the closed Pb-Zn-Cu Rammelsberg Mine (now a UNESCO World Heritage site) in the Harz Mountains or hard coal from the Ruhr Region in western Germany. With relation to real geological outcrops of geological and historical significance in many parts of Germany, the Geological Wall promotes knowledge of the natural and local history of our country and arouses interest in further geotopes in Germany.
What do we see?
On average, the wall is about 30 m long and 2 m high. It consists of 123 different kinds of stones coming from several regions in Germany: from the nearby Muschelkalk quarry in Rüdersdorf, the Harz Mountains, Saxony, Thuringia, Bavaria, Rhineland and from Silesia (today Poland).
The geological systems are arranged from the Proterozoic to the Cenozoic system, from right to left (Fig. 3). The different stones or stone layers are numbered.
Figure 3: Simplified model of the Geological Wall (extract from the information brochure).
Some sections of the wall are presented below.
The oldest rocks of the Proterozoic and Palaeozoic – the crystalline basement – are mainly arranged in Sections P to U. The centre is formed by granitic pluton, the Lusatian pluton in Saxony, which intruded during Cambrian time into Proterozoic rocks, dragging them along – illustrated by sloping older magmatic and metamorphic rocks. On one side, sideritic iron-bearing dikes break through these crystalline rocks. A typical iron cap is found on top. These dikes illustrate the famous iron ore deposits of the Siegerland in western Germany.
Section N shows a typical Permo-Carboniferous evolution in Central Europe. Lower Carboniferous folded and partly eroded slates and greywackes are covered by typical Upper Carboniferous series with sandstones, claystones and hard coal, as developed in several places in Germany. This exemplifies especially the Ruhr Region, where intensive hard coal mining established the basis for the German steel industry at the end of the 19th century. Some Carboniferous plant fossils illustrate the genesis of the hard coal from plants. The series is a good example for changing environmental and depositional conditions in a coal basin. The whole series is divided by a fault filled with a rhyolite symbolising the Permian volcanic activity as it developed near the surface in Sachsen-Anhalt, north of the city of Halle (Saale). A displacement of the layers left and right of the fault shows the connection of volcanism and tectonic activities. The red rhyolite, the so-called “Löbejüner Porphyr“, was a famous building stone in Berlin.
Section M“ shows another interesting well-known economic geological situation (Fig. 4). The section shows an inclined fold of Devonian slates as they occur in the Harz Mountains. This structure is accompanied by copper bearing schists of the world-famous Rammelsberg ore deposit, where copper and other metals were mined for more than 1000 years. Devonian reef limestones with well visible corals flank this series. They also contain a stalactite cavern as known from the caves opened to tourism in the Harz Mountains.
Figure 4: Section K–N with Carboniferous sedimentation (Hard coal – left and right), Devonian series with slates folded, Rammelsberg copper ore (centre), Devonian coral reef (34 inclusive cavern) and Permian volcanism (56) including fault (right).
The youngest part of the Palaeozoic is represented by copper slate and evaporites of the Upper Permian – called Zechstein in Germany. The exploitation of copper and other metals from the copper slate along the southern margin of the Harz Mountains in the so-called Mansfelder Revier began already in the Bronze Age and lasted up to 1991. This mining still continues today in Poland near Lubin. The weathering/oxidation of the copper is clearly visible from the green colours at the surface of the copper slate and the underlying sandstone.
The series of evaporites is only partly preserved. The salts are gone; only half of the gypsum and anhydrite remained.
The Mesozoic section shows examples of every geological formation, but main attention is given to the Muschelkalk. It is substantiated by geology around Berlin, which is dominated by young glacial sediments. The only outcrop of solid rocks here is an epirogenetic Muschelkalk formation at the eastern margin of Berlin. Since the Middle Age, the limestone has been quarried mainly for lime but also for building stone. The numerous fossil findings have attracted research in this field in Berlin since the 18th century. The whole sequence of the Rüdersdorf Muschelkalk is presented and well preserved in the sections E to G. However, the basal fibrous gypsum layer has been preserved only partially. It shows a surface as formed by the Ice Age, with a glacier valley and a limestone that has been polished by a glacier and displaying glacial scratches (Fig. 5). This has been arranged according to the theory of glaciation of northern Europe, which was very modern at that time. The glacial marks found in Rüdersdorf contributed to the confirmation of this theory.
Figure 5: Muschelkalk of the Rüdersdorf quarry with limestone polished by a glacier and with glacial scratches.
Another significant feature of the Muschelkalk is demonstrated in the Fe-Pb-Zn-deposit in Muschelkalk limestones in Maczeikowitz (now Maciejkowice, Poland).The real geological situation of this deposit has been re-created with Fe-bearing dolomite, galenite and Zn-carbonates. The Zn-Pb-Fe deposit region north of Krakow is among the most important mineral raw material occurrences of Europe (Cerny, 1989).
A typical sedimentary sequence with various alternating sandstones and limestones is presented in Section C, simulating the Jurassic and Lower Cretaceous series of the northwestern margin of the Harz Mountains. The layers are inclined (showing the situation that prevailed in the direction of the uplifting of the Harz Mountains during Cretaceous time). The base of this part is very specifically and descriptively designed. It is one of only two horizontal elements within the wall. Lower Jurassic oolithic iron ores with Ammonites of different sizes are arranged in the same way as they really occurred in Bad Harzburg. The mining of the iron ore was very intensive at the end of the 19th century and ammonites had been found in great quantities. Thus, they were able to build real ammonite fossils into this surface.
Another well-known landscape formed during Cretaceous times is illustrated in Section B: the “Elbsandsteingebirge” in Saxony. It is an easily interpreted image of successive sedimentation of clastic material into the Cretaceous marine basin on the eroded Palaeozoic granitic basement (Fig. 6).
Section A originally contained the loose sediments (sands, clay, gravel, brown coal) of the Cenozoic – those layers that form the subsurface of the wider Berlin region. Somewhere along the line these materials were lost and temporarily substituted for by Cretaceous sandstones.
Between the last two sections (Cretaceous and former Cenozoic) stands the most attractive part of the wall, illustrating Tertiary volcanism by basaltic columns (coming originally from Unkel (Rhineland) later replaced and extended from Stolpen (Saxony) forming a rosette cupola.
Figure 6: Illustration of the geological situation in the south of Saxony with basic granitic rocks, cretaceous sandstones and tertiary basalt volcanism.
Some erratic boulders of different sizes, found in the countryside around Berlin, are arranged along the flanks of the wall.
Teaching today
Currently the wall is used for education only on a few days per year. On some special dates geologists meet schoolclasses or the public at the wall to explain genesis and features of rock types, structures, problems of sustainability and weathering, to show minerals and fossils, with reference to raw materials and historic mining and the use of rocks in Berlin and to discuss questions connected with the geological underground.
The Geological Wall is situated in an old botanic park with many beautiful and interesting places, and is open to the public every day. Therefore, first of all, the Geological Wall has to be attractive for non-professionals. A modern, well-designed and self-explanatory information board is necessary. One didactic approach for a family with children could be based on riddles, which arouse children’s curiosity. For example, a riddle is posed: “Which animals built the biggest stones?”, so that the children can find the reef limestones with corals in the wall. Parents could help their children and learn something more about the reef limestones, derived from the Iberg in the Harz Mountains, of Devonian age (385 million years), inviting viewers to visit their beautiful stalactite caverns.
Meanwhile the grandparents could discover the basaltic rosette cupola, which illustrates the geological situation of the Upper Lusatia region in the South of Saxony. An explanation board should tell a story about the genesis of this geological setting beginning with the Proterozoic granodiorite, which was an island surrounded by ocean during the Cretaceous age; the erosion of that granodiorite produced sand, which was deposited along the coast (Fig. 7a) and later compacted by more overlaying sand, thus becoming sandstone. Volcanic activity in Tertiary times brought the basaltic magma breaking through the fissures of the granodiorite and the sandstone (Fig. 7b). The development of the basaltic columns near the surface and vertical to the cooling surface and reasons for their form and extent could be explained. Even the basaltic hill in a flat terrain tells a story about the weathering and erosion of older but weaker stones around the basaltic cupola – an example of an inverted relief (Fig. 7c).
Figure 7: Illustration of the genesis of basaltic columns.
Another story could be told about geoscience history and Alexander von Humboldt: in 1789, when he was a student in Bonn, he visited the “Unkelsteine” in the Rhineland, one of the most prominent basalt occurrences in Germany and source of the basaltic columns originally used in the geological wall. After the visit he took part in the dispute between the “Neptunists” and the “Plutonists” about the origin of the genesis of these columns and took up the position of the Neptunists explaining their genesis by the gradual drying of a marine sediment (https://de.wikipedia.org/wiki/Unkelstein).
But not only history could be taught. Geological topics like drinking water, soil, energy and raw materials were part of our daily lives 100 years ago and they are part of it even today. Where and in which form do our raw materials occur? How could we extract them? What do we need for “clean” energy or for electric cars? These issues are not taught – or only randomly taught – at school. The geological wall offers many possibilities to introduce into these subjects. Even if it were for this reason only, it is necessary to make every effort for the protection, renovation and didactical modernisation of the wall.
The Geological Wall through the ages and now
The wall has been altered, partly when it was moved to its current location and also due to the varying people in charge of it through time. Two main parts (salts and Cenozoic strata) are missing, some stones were lost to weathering or vandalism, some stones were substituted or improperly replaced and numbers got lost. From time to time, the surface has been cleaned with varying degrees of professionalism. Associated explanation plates and labels have disappeared.
Nowadays the wall is widely accepted by the authorities and the public. The geological survey of Berlin, the non-profit association of regional geologists (GBB) and the GrünBerlin GmbH association, which is responsible for the whole park, are paying attention to this attraction. Several measures have taken place during the last six years: professional mapping of stones, moss, joint mortar, defects and weathering damages, renovation of the packing, professional surface cleaning, partial replacement of missing stones and revision of the numbering. These measures were carried out by restorers,- restoration students of the University of Applied Sciences Potsdam in accordance with the agreement of monument protectors. The Federal Institute for Geosciences and Natural Resources (BGR) possesses a number of stones and fossils from historical outcrops in its geoscience collection and provided some for replacement. An interactive digital model of the wall with explanations of the stones has been developed (http://geowand.gruen-berlin.de/).The work was crowned with first success by the certification of the status of a “German National Geotope” in 2018. This award has outstanding importance because it acknowledges a geotope in a city of nearly four million people. Concepts for further restoration, re-creation of the lacking parts and explanations (both on the spot and digital) have already been developed and will be realised in the next few years, depending on the funding provided.
All involved parties and persons are very committed to a quick and appropriate realisation of the renovation and modernisation concept for the Geological Wall. The teaching of geological knowledge forms the base for understanding complex natural interactions and the attentive use of our natural resources. It should be involved into the school curriculum and could be taught directly in situ at the real natural stones of this fantastic, unique, historical but yet modern Geological Wall.
Location: Botanischen Volkspark Blankenfelde, Blankenfelder Chaussee 5, 13156 Berlin, Germany.
http://geowand.gruen-berlin.de
https://www.berlin.de/senuvk/umwelt/wasser/geologie/
References
Engel, H., Jersch-Wenzel, S. & Treue, W. 1990. Geschichtslandschaft Berlin – Orte und Ereignisse (History of Berlin – Places and Events), Vol. 3: Wedding, p. 8; Nicolai: Berlin.
Geowissenschaftler in Berlin und Brandenburg e.V. (Ed.) 2016. Geologische Wand im Botanischen Volkspark Pankow-Blankenfelde (Geological Wall in the Botanical Park in Pankow-Blankenfelde). Brochure.
Wutzke, U. & Liebram, C. 1999. Die Geologische Wand in Berlin und ihre Geschichte (The Geological Wall in Berlin and its History). Geohistorische Blätter, 2(1). p. 19-2.
Zache, E. 1896. Die Geologische Wand im Humboldthain zu Berlin (The Geological Wall in the Humboldthain in Berlin). P. Stankiewicz‘ Buchdruckerei: Berlin.
This article has been published in European Geologist Journal 48 – Geological heritage in Europe. Read here the full issue:
