Zeugenberg
A witness mountain (also Ausliegerberg ) is a single mountain in a layered landscape that was isolated by erosion processes from the layered plateau to which it originally belonged.
Fundamentals and demarcation
Stratified landscapes are characterized by alternating layers of layers made of erosion and weather-resistant (competent) rocks and layers of significantly less erosion and weather-resistant (incompetent) rocks. The competent rocks are called step formers , the incompetent ones as slope or base formers . A Zeugenberg usually has a flat but steep-walled cap made of step-forming rock, the upper slope , which protects the underlying rocks from the base-forming rock, the lower slope , from rapid erosion. One speaks here of a reinforcement of the lower slope rock by the upper slope rock.
Witness mountains are not to be equated with island mountains , which are isolated mountains on (often geologically very old) hull surfaces. Tectonic cliffs are also areas that have been isolated by erosion from the rock formation to which they originally belonged, but this rock formation is a tectonic blanket in a mountain range , i.e. the formation of tectonic blankets also takes place in a geologically completely different environment than that Formation of witness mountains instead.
Emergence
In the following, two scenarios are described according to which mountains of witnesses arise.
With shallow layers
Classical monadnocks occur in stages layer landscapes with flat incident layers by the erosive action transverse to the brushing running nature (so-called subsequente flows). This isolate the topographically highest and exposed part of a layer step, the steps First , the lower and upper slope future through recess in the subjacent Hangbildner from topographically and still partially covered by younger strata of the layer level. Rivers or brooks flowing across the brush (the so-called obsequent and resequent rivers) also ensure the transverse structure of the old step ridge. The result is mountains of witnesses that stop in front of the new front of the main step. As long as the upper slope is still connected to the main step, one speaks of a cantilever, a spur, a ledge or a "mountain peninsula". The surrounding valleys are known as step edge bays, step edge valleys or face valleys . Only after a clear separation from the main level does one speak of a mountain of witnesses. Within the slope-forming horizon, however, a connection to the receding main level can still exist for a long time. Such mountains of witnesses only form when the layers fall at an angle of 1 to 2 °. If the layers are steeper, the difference in height between the old and the new step ridge is so great that the old step ridge and potential overhang has already been eroded before the rivers have isolated it from the rest of the layer step.
By reversing relief in tectonic trenches
Another possibility of the origin of the Zeugenberg is the location on a moat . A step former on a tectonically sunken clod is attacked far less by erosion than in the non-sunken areas, on the one hand, because surface-like erosion forms always attack higher-lying terrain more than lower-lying terrain and, on the other hand, because in the non-sunken area the layer contact to the The underlying base former is also topographically higher and can be reached more quickly by the intersecting rivers. If the rivers in the non-sunken area have only deepened to this underlying horizon, the river valleys there widen and a. relatively quickly due to spring erosion, so that the actually relatively erosion-resistant rock of the step former is now quickly cleared. Finally, the step former is completely removed in the non-lowered area. Since the base former is significantly less erosion-resistant than the step former on the tectonically submerged clod, the terrain of the non-sunk area is deepened significantly faster than that of the sunken area and the step former preserved there is modeled out of the landscape as a witness mountain. Such a process falls under the umbrella term relief reversal .
meaning
The isolated mountains “testify” to the earlier coherent distribution of certain layers far beyond today's main distribution area. A whole Zeugenberg landscape can develop when the steps are moved backwards or broken down. A well-known example of this is Monument Valley .
Examples
Well-known witness mountains of the Jura layers between Coburg and Basel
Unfolded, slightly inclined layers of the Jura extend between Coburg in the northeast and Basel in the southwest . They belong to the south-west German layered landscape or to the Jura Mountains in the broader sense and are developed into mighty layers, especially in the White Jura (in Switzerland especially in the Brown Jura ). In the entire step area, witness mountains and partly also witness mountain landscapes have developed.
The most important witness mountains of the Franconian Alb are (first from north to south, then towards (south) west):
- Staffelberg (540 m)
- Walberla (532 m)
- Hetzleser Berg (549 m)
- Moritzberg (603 m)
- Dillberg (595 m)
- Buchberg (591 m)
- Sulzbürger Schlossberg (567 m)
- Neubürg (587 m)
- Schlossberg (607 m)
- Hesselberg (689 m)
Important witness mountains of the Swabian Alb (without "pseudo witness mountains", i.e. (partially) free-standing mountains of volcanic origin such as Limburg ) are (from northeast to southwest):
- Ipf (668 m)
- Cold field (781 m)
- the Three Kaiser Mountains : Stuifen (757 m), Rechberg (708 m) and Hohenstaufen (684 m)
- Michelsberg (724 m, near Geislingen an der Steige )
- Achalm (707 m)
- Farrenberg (821 m)
- Rossberg (870 m)
- Zoller (858 m) with Hohenzollern Castle
- Burgfelden plateau floe (954 m)
- Plettenberg (1002 m)
The area of the Baarjura is almost completely a witness mountain landscape. It includes (without "pseudo witness mountains"):
- Hohenkarpfen (912 m)
- Lupfen (976 m)
- Möhringer-Berg-Lindenberg-Scholle (949 m)
- Fürstenberg (918 m)
- Length (921 m)
- Eichberg (914 m)
- Buchberg (880 m)
The most important witness mountains of the so-called Table Jura in Switzerland between Bad Zurzach and Pfeffingen are (from east to west, here too the shift level has already largely been transformed into witness mountains and outlying landscapes):
- Geissberg (700 m)
- Heuberg (558 m)
- Schinberg (722 m)
- Frickberg (650 m)
- Farnsberg (758 m)
- Sunnenberg (632 m)
- Chienberg (741 m, with Sissacher and Rickenbacher Flue)
Witness mountains of the low mountain range threshold
-2.jpg)
Local witness mountains also play a role within the low mountain range threshold north of the actual stratified landscape, which is more characterized by clods with raised basement . Especially in the Thuringian Basin (with edge plates) , which represents a more or less closed layered landscape, and its surrounding area, there are many striking mountains that bear witness to the limestone step.
West and north of the north-western edge plate are mainly Gobert and Ohmgebirge along with bleach Röder mountains to call that forth from its scope even as a witness Mountains can be designated and higher highs reach than the actual edge plate. In addition, there are numerous dome-like individual witness mountains west of the Ohm Mountains and north of Gobert and Obereichsfeld.
To the southeast of the Ilm-Saale plate , which together with the Ohrdrufer plate adjoining it to the southwest, forms the southeast edge plate of the basin, witness mountains appear sporadically, such as B. Leuchtenburg and Dohlenstein near Kahla or the Kulm near Saalfeld . Strictly speaking, the Singer Berg , which is often listed as the highest mountain of the Ilm-Saale Platte, is a witness mountain of the Reinsberge in the east of the Ohrdrufer Platte.
Southwest of the Thuringian Basin, the two northernmost peaks of the Rhön , Dreienberg and Landecker Berg , are not basalt chimneys, but witness mountains of the shell limestone level there.
The Muppberg near Neustadt near Coburg is a prominent witness mountain of the red sandstone level . He is a witness mountain of the southeastern red sandstone slope of the Schalkau plateau .
See also
literature
- Lexicon of Geography I. 2001, p. 108.
- Lexicon of Geography III. 2002, pp. 189-190.
- Lexicon of Geosciences IV. 2001, pp. 400–403.
- Harald Zepp : Geomorphology. 2nd Edition. Paderborn 2003, chapters 12.3 and 14.3.
Individual evidence
- ↑ a b Lars Wartenberg: Fractional stages and layer stages. GRIN Verlag, 2003, p. 8, ISBN 978-3-640-35670-6
- ↑ Gottfried Hofbauer, with the collaboration of Rudolf Biemann, Norgard Mühldorfer, Werner Straussberger, Hans Stuhlinger and Barbara Thies: The honorary citizen (the "Walberla"): Aspects of the emergence of a witness mountain in front of the Northern Franconian Alb. www.gdgh.de/Berichte/B12, 2007 ( PDF 2.7 MB)