The Swiss Mittelland ( French plateau suisse, le plateau ) is one of the three mountainous regions of Switzerland with around 30 percent of the area, alongside the Jura and the Alps .
It includes the partly flat, but largely hilly area between the Jura and the Alps, and is on average at an altitude of 400 to 600 m above sea level. M. Favored by its location in the basin , it is by far the most densely populated region in the country and therefore the most important large area in terms of economy and transport .
The Swiss plateau is clearly delineated in the north-west and north, both geographically and geologically, by the elongated mountain ranges of the Jura . In the south towards the Alps , the border is not uniformly defined. The criterion for the delimitation is usually the relatively abrupt rise in some places to heights of over 1500 m above sea level. M. , calcareous Alps and plateaus , partly to the mountains of the subalpine Molasse . Occasionally the regions of the higher Mittelland, in particular the Freiburg hilly landscape , the Napf area , the Tössbergland and parts of the Appenzellerland are counted as part of the Swiss Pre-Alps in the narrower sense. However, if you only consider the mountainous regions, the Alpine foothills clearly still belong to the Central Plateau. Lake Geneva forms the southwestern border of the Swiss Plateau, and Lake Constance and the Upper Rhine form the northeastern border .
Geologically, the Central Plateau is an elongated sedimentary basin that extends beyond the Swiss national borders. In the south-west on French territory, the basin narrows in the Genevois and ends at Chambéry , where the Jura and the Alps join. Beyond Lake Constance, the Mittelland continues in the southern German and Austrian Alpine foothills .
On Swiss territory, the central plateau has a length of around 300 km with a width that increases from southwest to northeast. In the Geneva area the width is 20–30 km, in the Bern area around 50 km and in eastern Switzerland around 70 km.
Numerous cantons have a share in the Mittelland. Complete Swiss cantons are Zurich , Thurgau and Geneva ; The cantons of Lucerne , Aargau , Solothurn , Bern , Friborg and Vaud are mainly located in the Central Plateau ; smaller proportions can also be found in the cantons of Neuchâtel , Zug , Schwyz , St. Gallen and Schaffhausen .
Due to numerous deep wells for oil and natural gas , the rock sequences in the Swiss plateau have been researched relatively well. The base is formed by the crystalline basement that emerges in the central massifs of the Alps as well as in the Black Forest and the Vosges , but lies deep underground in the Jura and Central Plateau region. About 2500 to 3000 meters below the surface of the earth, and also significantly deeper near the Alps, one encounters these crystalline rocks when drilling in the central plateau. An unfolded sequence of layers of sediments from the Triassic , Jurassic and Cretaceous ages lies over the basement . She too is not open anywhere in the Swiss Plateau. Its thickness gradually decreases from 2500 to 800 meters from west to east. Like those of the Jura Mountains, these layers were deposited in a relatively shallow marginal sea of the Tethys Ocean . The molasses sediments came to lie on the Mesozoic layers . These consist of erosion products from the Alps, mostly Nagelfluh (conglomerates), sands , marls and clays , which have solidified into rock under the pressure of overlying sediments. The top layer is made up of gravel and other loose rock that was transported by the ice age glaciers.
Geologically of the greatest importance in the Swiss Plateau are the mighty molasses - sediments that were deposited on the young Alpine edge as a result of mountain erosion. The layer thickness of the molasses increases from west to east (at the same distance from the Alps). The rivers from the Alps at that time - generally not congruent with today's river network - built up significant alluvial fans at the foot of the mountain. The most important examples of this are the Napf and Hörnli flood fans, there were other fans in the Rigi area , in the Schwarzenburgerland and in the area between eastern Lake Geneva and the middle course of the Saane .
The erosion material was sorted according to its grain size. Coarse-grained material was mainly sedimented near the Alps as soon as the flow speed of the water as a transport medium became too low to keep the coarser stones in suspension. In the middle part of the basin you will mainly find the finer-grained sandstones and on its northern edge near the Jura clay and marl.
History of the Molasse in the Swiss Plateau
In the first period of the Tertiary around 60–40 million years ago, the area of today's Swiss Plateau was a karstified limestone plateau that sloped slightly to the south and was also drained in this direction. In the period that followed, this plateau was flooded twice by the sea due to uplift and subsidence processes in connection with the formation of the Alps . A distinction is therefore made between the corresponding deposits as marine molasses and freshwater molasses, whereby the latter should not primarily be understood to mean sediments in freshwater lakes, but above all deposits from river systems and wind transport (i.e. more of a "mainland molasse").
- Lower sea molasses (about 37–30 million years ago): Gradually the limestone plateau subsided and a shallow arm of the sea penetrated, reaching in the east as far as the Carpathian Mountains. The sediments consisted of fine-grained sands, clays and marls; Nagelfluhfächer did not exist yet, because the actual uplift of the Alps only begins at the end of this period.
- Lower freshwater molasses (about 30–22 million years ago): The sea receded on the one hand because of uplift processes, on the other hand because of a worldwide sea level drop. Together with the folding of the Alps, the mountain erosion set in and the first Nagelfluh fans emerged.
- Upper sea molasse (about 22-16 million years ago): A shallow arm of the sea penetrated again and the formation of the nagelfluh fans of the Napf and Hörnli began.
- Upper freshwater molasses (about 16–2 million years ago): The sea now finally retreated. The construction of the Napf and Hörnli fans (as well as other smaller alluvial fans) continued, so that at the end of the period they reached a layer thickness of around 1500 meters.
In the period that followed, the western part of the Central Plateau was again heavily lifted, as a result of which the sediments of the upper sea and freshwater molasses were largely eroded again in this area.
Petrified snails, mussels and shark teeth are characteristic of the sediments of the sea molasses. In contrast, the freshwater molasses contains fossils of typical mainland mammals but also remains of the subtropical vegetation of that time (e.g. palm leaves).
Ice Age overprinting
The landscape of the Swiss Plateau got its current form during the impact of the Ice Age glaciers. During all known alpine glaciation stages ( Günz , Mindel , Riss and Würm glacial periods ), enormous glacier ice masses advanced far into the Swiss Plateau. The interglacial warm periods caused the glaciers to retreat into the high Alps (sometimes less extensive than today), and subtropical vegetation spread in the Swiss Plateau.
During the glacial period , the Rhone glacier divided into two arms at the exit of the Alps, one of which extended over the entire western central plateau to the regions of Solothurn and Aarau. In the Bern area, it united with the Aare glacier. Also, the Reuss, the Linth and Rhein glacial pushed partially prior to the Jura. The ice masses formed the land on the one hand through deep erosion, on the other hand through deposits of ground moraines, often several meters thick (very finely ground rock flour) and through the deposition of gravel by the rivers in front of the glaciers.
Traces of the older Günz and Mindel glacial periods are only left in a few places, as they were removed or relocated by the glaciers of the subsequent glacial periods. The glaciers reached their greatest extent in the Riss Cold Age, during which the entire Central Plateau, except for the Napf area and the Tössbergland, was covered by ice. By far most of the traces are evidence of the Würm glacial period, which began around 115,000 years before the present. The terminal moraines of the glaciers and the deposits of the various retreat stages have been preserved.
Because of the strong glaciation and the large river systems in Switzerland, loess deposits are only found in the far north around Basel , Baden and Schaffhausen .
If you look at the map, you can still see the direction of flow of the Ice Age glaciers. The expanse of the Rhone Glacier to the northeast is shown by the course of the valleys ( Broye , Glâne ) and lakes ( Neuchâtel , Biel and Murten ) in western Switzerland, which are parallel to the Jura and the Alps . Reuss and Linth glaciers have created the valleys (including the Wigger , Suhren , See and Reuss valleys ) and lakes ( Lake Zurich , Greifensee , Hallwilersee , Sempachersee ) of the central plateau that run from southeast to northwest . In northeastern Switzerland, the Rhine Glacier left mostly traces running in an east-west direction ( Thurtal , Untersee of Lake Constance ). In some places there are characteristic drumlins made of pressed ground moraine material, which usually appear in larger swarms, particularly typical in the Zurich Oberland , in the Hirzel region, in the Lake Constance region and between the Reuss valley and the Baldeggersee .
Other important legacies of the glaciers in the Central Plateau are, in addition to the lake and river system, the erratic boulders , which can be found scattered across the entire area. These sometimes huge erratic blocks (for example near Steinhof ) made of foreign rock, mostly granite or gneiss, which only occur in the high Alps, were among other things the key to the foundation of the Ice Age theory in the 19th century, since transport by hydropower alone was physically not possible is.
Finally, the gravel deposits in the valley floors of the Central Plateau are a testament to the Ice Ages. During the glacier period as well as when the glaciers advanced and retreated, thick layers of gravel were deposited in the valleys, which were eroded away with the exception of a few remains in the subsequent warm period. Many valleys therefore have a terrace system: the lower terrace consists of gravel from the Würm Ice Age , the high terrace consists of deposits from the crack ice age . Sometimes gravel from the older ice ages can also be found.
Although the Swiss Central Plateau is a basin, it is by no means to be classified as a flat landscape, but, depending on the region, has a very diverse natural structure. Important elements are the two large lakes, Lake Geneva and Lake Constance, which border the Swiss plateau in the south-west and north-east. West-central is characterized by plateaus ( Gros de Vaud , to 600 m above sea level. ) And Molassehügelländer ( Jorat until 900 m asl. , Freiburg hills, 600- 1200 . M asl ), in which part deep valleys are carved in. Only near the Jura is there an almost continuous depression with the valley of the Venoge and the Orbe plain , which through the cross bar of the Mormont , over which the watershed between the catchment areas of the Rhone and Rhine at only 500 m above sea level. M. runs, is divided into two parts. The Seeland forms the largest flat area of the Central Plateau, but even in it there are individual molasse ridges. To the east, there are now various hilly countries that gradually become lower towards the north. Another larger area is the level of the water office through which the Emme flows. The Aare , which mostly flows in a wide valley along the southern foot of the Jura , absorbs all rivers coming from the higher plateau and the Alps like a gutter.
The central plateau is characterized by a number of south-east-north-west oriented broad ridges (including Erlosen , Lindenberg ) and further valleys in between, some with lakes (Sempacher, Hallwiler and Baldeggersee). The eastern end of this is formed by the Albis chain , which, together with the Heitersberg chain , creates a barrier running across the midland between the Jura and the Alps, which can only be passed in a few places by the high-performance modes of transport, mostly in tunnels.
The eastern central plateau is divided into the valleys of the Limmat (with Lake Zurich), Glatt (with Greifensee), Töss and Thur . In between there are hilly lands, and in Thurgau there are also broad molass ridges ( Seerücken , Ottenberg ).
Two hilly areas stand out clearly from the landscape forms mentioned. These are the Napfbergland (with heights up to 1408 m above sea level, also the highest point on the Central Plateau) and the Tössbergland (Chrüzegg up to 1314 m above sea level ), both remains of the tertiary Nagelfluh alluvial fan. These have been severely eroded over time, but due to their altitude, they have not been shaped by ice age glaciation. This is why deeply indented, steep-walled valleys (ditches) and a heavily branched, dense network of waterways developed.
The Swiss plateau lies in the transition area from a wet maritime to a continental temperate climate with predominant winds from the west. In the lower central plateau, the mean annual temperature is around 9–10 ° C. In January, the Lake Geneva region and the near-shore areas of Lake Neuchâtel and Lake Biel have the highest mean temperatures of around +1 ° C. At the same altitude there is a slight east-west gradient; In the coldest month, mean temperatures of –1 ° C are reached in the Lake Constance area. The mean temperature in July in the Geneva area is +20 ° C, but an average of 18–19 ° C is also reached along the entire southern foot of the Jura, and around 16–18 ° C in the higher regions closer to the Alps. The Lake Geneva region is also favored in terms of the average annual sunshine duration with over 1900 hours, in the rest of the Central Plateau it is 1600 (especially in the east) to 1900 hours.
The mean annual rainfall ranges between 800 mm near the Jura, 1200 mm in the higher plateau and 1400 mm on the edge of the Alps. The driest regions of the Central Plateau are located in the lee of the High Jura between Morges and Neuchâtel. Nowadays there are fewer than 20 snow cover days in the warmest regions on Lake Geneva and Lake Neuchâtel, and between 20 and 40 per year in the rest of the Central Plateau, depending on the altitude.
In the winter months, when the weather conditions are poor in exchange, a cold air lake forms in the Swiss Plateau, which usually results in fog or high fog. Then the entire Central Plateau lies under a thick blanket of fog for several days, sometimes even weeks, while the neighboring areas (Jura and Alps) benefit from the beautiful weather. The bise , a cold north-easterly wind, is typical in high fog . Due to the canalization in the Central Plateau, which is becoming narrower towards the west, this reaches its greatest strengths in the Lake Geneva area, where average wind speeds of 60 km / h and gust peaks of over 100 km / h are not infrequently recorded in the classic Bisen situation. The regions of the central and eastern plateau near the Alps sometimes enjoy warm foehn winds .
The mixed deciduous forest with the main representatives beech and fir is dominant in the Swiss plateau . In many places there are large stands of spruce planted for economic reasons; By nature, spruce hardly occurs in the lower layers. In favored, warmer and drier places in the Lake Geneva region, in Zealand and in northern Switzerland from the mouth of the Aare to Schaffhausen, oaks , linden and maple are the most important trees in the forest.
Although the Central Plateau only makes up around 30 percent of the area of Switzerland, around 5 million people or slightly more than two thirds of the resident population of Switzerland live here. Therefore, the Central Plateau is densely populated with 380 inhabitants per square kilometer. All Swiss cities with over 50,000 inhabitants (except Basel and Lugano) are located in the Swiss Plateau , the most important of which are Zurich , Geneva , Bern and Lausanne . The main focus of settlement is therefore also in the area of the agglomerations of these cities. The Zurich agglomeration alone has almost 1.3 million inhabitants. Other densely populated areas lie along the southern foot of the Jura and in the Lucerne , Winterthur and St. Gallen area . In contrast, the regions of the higher Central Plateau in the Jorat, Napf area and Tössbergland are sparsely populated, predominantly small farming villages and scattered individual farms.
The majority of the population in the Swiss Plateau is German-speaking; French is spoken in the western part. The language border has existed in almost the same place for many centuries and is not tied to a geographical dividing line. It runs from Biel via Erlach , Murten and Freiburg to Schwarzsee in the Freiburg Alps. The city of Biel / Bienne is officially bilingual; In Murten (Morat) and Freiburg (Friborg), school lessons are offered in their language for the French-speaking and German-speaking minorities. Places along the language border usually have a German and a French name (see also: List of German names for Swiss places , List of French names for Swiss places ).
As part of a brief outline of the settlement history, the following points should be mentioned: The first settled areas in the Neolithic were the lake and river banks of the Central Plateau (pile dwellings). The first villages consisting of wooden huts emerged from the 3rd century BC after the immigration of Celtic tribes. Urban settlements with stone houses developed during the Roman period, which began in 15 BC with the annexation of the Helvetii territory into the Roman Empire under Emperor Augustus and lasted until the end of the 3rd century AD. The three most important places in Roman times were Aventicum ( Avenches ), Vindonissa and Colonia Iulia Equestris ( Nyon ). They were connected to one another by a well-developed network of military roads. After the retreat of the Romans, the western plateau was settled by the Romanized Burgundians, the central and eastern plateau by the Alemanni, which established the language border.
During the Middle Ages, numerous cities were founded, mainly in the lower Central Plateau, which is more climatically located. Around 1500 there were already around 130 cities connected by a dense transport network. With the industrialization in the 19th century, the cities quickly gained in importance and especially from 1860 onwards a rapid population growth began, which lasted for about 100 years. The next trend reversal began around 1970 when urban exodus began. As a result, the communities close to the city grew disproportionately, while at the same time the core city lost inhabitants. In recent times this growth belt has been shifting further and further outwards, and urban sprawl is continuing.
Thanks to its favorable climate and fertile soils, the lower western plateau is the most important arable farming region in Switzerland. The predominant soil type is the parabrown earth , in higher altitudes the brown earth . The main crops used in arable farming are wheat , barley , maize , sugar beet and potatoes ; especially in Zeeland also has vegetable places high priority. Vines are planted in favored locations along the lakes, at the southern foot of the Jura as well as in the Zürcher Weinland and Klettgau . Meadowland with dairy farming and beef cattle farming predominates in the eastern Central Plateau and in the higher regions of the rest of the Central Plateau. Especially in the canton of Thurgau has fruit growing (apples) very important. As a result, the groundwater in the Swiss Plateau is heavily polluted with pesticides , so that the limit values in drinking water are exceeded in many places, e.g. B. by breakdown products of chlorothalonil .
The forests of the Central Plateau are used for forestry ; there are numerous spruce forests all over the country. Because of the valuable timber yield , the spruce trees are often planted in pure stands.
The Central Plateau is also Switzerland's core region in terms of the industrial and service sectors. As a traditional branch of industry, the textile and clothing industry is to be mentioned, especially in the central and eastern plateau; however, it has lost importance in the last few decades. The most important branches of industry today are machine and vehicle construction, electrical, electronic, precision engineering and optical industries as well as metal construction. Both domestic agricultural products and imports are processed in the food and beverage industry. Wood and paper processing are also important.
Like the rest of Switzerland, the Central Plateau is poor in natural resources. However, thanks to the advancement of the glaciers during the Ice Ages, there is enough gravel and clay . Gravel mining in the area of the Ice Age gravel terraces is widespread in the valleys of the entire Swiss Plateau and meets the needs of the building materials industry.
Hydropower is used to generate electricity by means of numerous river power plants. All four Swiss nuclear power plants are also located in the Swiss Plateau. These are the Gösgen , Leibstadt and Beznau I and II nuclear power plants .
Due to the relatively simple topography by Swiss standards and the dense population, the transport network in the Central Plateau is very well developed. The most important transversal route, the backbone of the Central Plateau, so to speak, is the A1 motorway , which runs from Geneva via Lausanne, Bern, Zurich and Winterthur to St. Gallen and connects all major cities. Your last section between Yverdon-les-Bains and Estavayer-le-Lac was only opened in 2001; it should help this previously structurally weak Central Plateau region to achieve an economic upturn. The A2 motorway as the Swiss north-south axis crosses the Swiss Plateau between Olten and Lucerne.
The railway network has always been very dense. As with the A1, all major cities are directly connected by train, with two main lines between Lausanne and Olten. The Midland line leads from Lausanne via Freiburg and Bern to Olten, the Jura foothills line runs along the foot of the Jura and opens the cities of Yverdon-les-Bains, Neuchâtel, Biel / Bienne and Solothurn. There was a quantum leap on December 12, 2004, when the new Mattstetten – Rothrist line ( Bahn 2000 ) was opened, which shortened the travel time on this line by 15 minutes. A train ride between Bern and Zurich now takes a little less than an hour.
The two most important Swiss airports are located in the Swiss Plateau: Zurich Airport on the Glattal plain near Kloten and Geneva Airport on the border on the north-western edge of the city. Bern, the de facto capital of Switzerland, only has the small Bern-Belp airport .
Compared to the Alps, the Swiss Central Plateau, especially the rural area, is less geared towards tourism and tourism; it mainly forms a transit region. Only the larger cities with their sights, especially the old towns of Zurich, Bern and Lucerne, but also St. Gallen, Friborg, Solothurn, Geneva and Lausanne, attract city tourism. As a natural attraction, the Rhine Falls near Schaffhausen are a special magnet for tourism. The Lake Geneva region and the three lakes region with Lake Neuchâtel , Lake Biel and Lake Murten , where the 2002 national exhibition Expo.02 took place , also benefit from tourism . In Baden , Bad Zurzach , Schinznach-Bad and Yverdon-les-Bains with their thermal baths you can also find spa tourism. Cycling and hiking tourism are playing an increasingly important role on the rivers Aare, Emme, Reuss and Rhine.
- Christian Lüthi: Mittelland (region). In: Historical Lexicon of Switzerland .
- Toni P. Labhart: Geology of Switzerland . Ott Verlag, Thun 2004. ISBN 3-7225-6762-9 .
- Andre Odermatt, Daniel Wachter: Switzerland, a modern geography . Neue Zürcher Zeitung, Zurich 2004. ISBN 3-03823-097-9 .
- ↑ Sand wall for the sand martins near Giebenach Auf: Verein Naturnetz
- ↑ Investigations on Lössen in Northern Switzerland by Gouda Hassanein Gauda, from 1958, on: Geographica Helvetica
- ↑ Federal Office for the Environment : Chlorothalonil Metabolites in Groundwater: First Assessment of the Nationwide Pollution. In: admin.ch. May 12, 2020, accessed May 12, 2020 .