Cuesta
As escarpment or cuesta landscape geomorphology refers to a site or relief form that builds up from slightly tilted, almost parallel sequence of rock layers. Your expression and slope mainly depends on the weathering resistance and location of their constituent rocks off.
- 3.1 -layer sheet
- 3.2 layer comb
- 3.3 layer rib
- 3.4 layer and layer threshold ramp
- 9.1 General
- 9.2 Special
General
Prerequisite for the formation of layered levels ( and related forms layer panel layer comb, rib layer, layer and layer ramp threshold) is usually a layer package with different denudation resistant rock strata. These layers were then cut by weathering and / or erosion, which has the typical appearance of the result.
The transitions between stage, table, comb, rib, ramp and threshold are fluid. Other important factors are slope and thickness of the layers involved and the type and energy of erosion and weathering. Layers are usually dominated by reliefs heterolithisch, that is, consisting of a plurality of such layers of rock. However, different degrees of weathering in a layer can also lead to a homolithischen layer relief. In Central Europe layer reliefs found mainly in West Germany ( Southwest German cuesta land ) and in the area south of Lower Saxony North Hessen-Thüringen.
Escarpment in the narrow sense
Commonly are also the terms " country level" and " cuesta relief".
Description / Form Treasure
Levels and Sockelbildner
Ideally, at the beginning of the development stage of a layer usually uplift and associated skew a layer package with lying on top resist fuller and more resilient bottom-mounted rock layer by about 1-5 °. To form the stage, it comes through erosion to the underlying more ductile layer. The layer the overlying more resistant denudation, ( "harder" ) rock called Stufenbildner and forms the raised portions of the stage (see 2.1.2). The Sockelbildner is the layer of the lower-level, less denudation resistant ( " softer" ) rock.
The degree and direction of the layers are inclined position with the geological technical terms "Fallen " (or " dip " or " layer (s) fall " ) and described " painting ".
Front and Back
The transverse profile is clearly asymmetric and is divided generally into face and back. Front of the face is the foreland of the stage to the back follows the corresponding hinterland.
The face especially a layer stage is called stage slope. This is divided into stages forehead (also called " upper slope " and "upper levels Hang" ), which is the upper, steeper, occupied by Stufenbildner slope area, and base slope ( also " slope " and "lower levels slope "), which is the lower (sometimes average ), less steep, occupied by Sockelbildner slope area. The base of a slope can be divided into a steeper Hangfußzone and less steep to flat foot surface. In step slope can be at the Schichtfuge ( ie layer boundary ) find a source horizon between stage and Sockelbildner, quite often, the boundary between the upper and lower slope indicating.
The back, especially the Escarpment is called step surface (also called " back stage " and " Country Terrace "). You rarely falls together with the roof surface of the step generator and can carry younger rocks, which are mostly cut in very shallow angle. If necessary, the transfer is to Sockelbildner a next stage.
The step slope (also "contrary stage " ) is mostly as a front stage formed. A front stage pointing towards the bulge of the layer package, away from the layer traps. The rarer eight stage (also called " compliant stage " ) shows, however, in the direction of the layer falling. The step height is dependent on the thickness of the step generator.
The ridge marks the highest points of a (front ) stage. The escarpment forms are not always trained in cutting edge of slope and area. Hipped called the area between the ridge and eaves. From the occurrence and location of the eaves, are three types of stages: First stage (also called " Traufstufe without hipped " ): First and eaves fall together. Eave hipped stage (also called " Traufstufe with hipped " ): First and eaves do not coincide, hence the intermediate hipped is rather part of the stepped surface. Walmstufe: no eaves formed ( slope slope upwards steadily goes to zero ), hipped is therefore more likely part of the slope.
The horizontal run of stairs slope regions of a layer stage shows due to erosion and steps backward displacement predominantly strong zerlappt and sinuate: it occurs step edge bays, step edge valleys ( front side valleys ), mountain peninsulas, projections, terrain spurs, outrigger and witnesses mountains ( Ausliegerberge ). Unlike Berghalbinsel, outrigger projection, and a spur is likewise still connected to the main stage in Stufenbildner, however, the original step surface between the outrigger and the main stage has been eroded. A witness Mountain (also called " Ausliegerberg " ), however, is no longer connected in the area of the step generator with the main stage, but usually in the range of the base generator. ( Nota bene: " outrigger " is therefore not the same as " Ausliegerberg ". ) Witnesses mountains and outrigger occur both with, and without, their own levels of surface.
Cuesta landscape
When multiple contiguous occurrence of cuesta is called a cuesta landscape (also called " cuesta " or simply " steps Country "). The removal of the front steps dependent upon one another of incidence and thickness of the layers. At low powerful and rapidly changing layers small steps can occur.
From an anticlinal stages country speak when front steps of several tectonic units of contiguous landscapes stages facing each other and to the common curvature center hinz own (eg, Southern Germany and Northern French anticlinal country levels ); in a synclinal - country levels show the front steps away from each other, usually in the center is a hollows or pelvic area ( such as the synclinal -stage land around the Paris Basin ).
Directions of flow of watercourses
The courses of the rivers in a cuesta landscape or on a layer level have specific designations ( mark-word " macros "). The consistent water flow in the direction of the layers falling, but have existed before the emergence of the stage. The resequenten waters also flow in the direction of the layers falling, but are developed only after the emergence of the stage. The obsequenten waters flow opposite to the con and resequenten waters and have an important role in the return displacement levels. The subsequenten waters flow in the layer coating, tend to parallel to the stage, often as a step edge flow.
Creation / development
The time of origin of cuesta is prior to the Holocene ( ancient form). In the Holocene was and is only to source erosion, landslides and rockslides ( landslide of Mossingen ). The pace imposed by the headward erosion levels relocation was, based on Central Europe and Quaternary, about 200 meters to 60 kilometers. Specifically, details of development time, development history (type of ablation ) and rate of redeployment controversial.
Special Shapes / related forms
Layer board
Layer panel reliefs occur in horizontal or very flat-bedded layer packets (to drop about 0-1 ° ), some with large plateau-like shapes. The panel surface is dominated by the roof surface of the panel builder. Stages slopes can be found everywhere. Outrigger and witnesses mountains called tepuis, smaller forms occur as rock towers and spiers. With rapid fluvial canyons depression may occur. Examples of layer panel landscapes in Central Europe are the Rheinhessen plateau, the North Hessian mesas and the Elbe Sandstone Mountains, in North America the Plateaux of Colorado with the Grand Canyon. Similar landscapes, such as layer board landscapes, can be found in large basalt and lava flows.
Comb layer
Layer comb reliefs may occur (more than about 10-12 ° dip ) with steeply dipping layers. The ridges of the dissected denudation more resistant layer ( Kammbildner ) run contrary to the cuesta largely straightforward, it found no outrigger and the like. The face is, forehead slope. The back is the abdachende towards the layers falling back slope ( a surface layer as in stages is not formed ). The cross section can also be symmetrical. Add a layer of comb landscape can be found between the combs Ausraumzonen.
Layer ridge landscapes occur, for example in folded sedimentary rocks and are therefore mainly found in fold mountains or tectonically unstable areas. The Teutoburg Forest is a formed of Cretaceous sandstone layer comb. The "ridge and valley topography " of the Appalachian Mountains is characterized by the appearance of layer combing.
Layer rib
Layer ribs ( landscapes ) occur in vertical or very steeply dipping strata. When folded mountains they may be exacerbated in burrs.
Layer and layer threshold ramp
Layer and layer ramp threshold are transitional forms between the coating stage or comb on the one hand and torso area on the other hand, with little steep faces ( maximum of about 8-10 °). Cause may be an already very far ablation was performed or a comparatively little resistant ramp or Schwellenbildner. Ramps are asymmetrical and have ramp slope and ramp surface, thresholds are symmetric (no significant relief difference between front and back).
Significance of the Mesozoic strata
Layer reliefs found in Europe mostly in the sedimentary rocks of the Mesozoic overburden.
Importance of Klüftigkeit
It is not only the different erosion resistance of the rock layers, which leads to the formation of layered stages, but also the different Klüftigkeit ( water permeability ) of the rock. This property leads to the formation of layer sources, which play a role in the retrogressive erosion.
Concept of structural form
The Escarpment is in the geomorphological sense to form a structure. This means that their origin was attributable primarily on geological- tectonic conditions. In contrast, hanging sculpture forms (such as the stage or table surfaces like hull surfaces ) mainly with exogenous processes together.
History of Research
The question of whether the layer surface is a Akkordanz or a sculpture form, combines the cuesta research on the closest to the fuselage stages of research. A first level phase witnessed the cuesta research in the mid-19th century. The development of the cuesta research began in the Anglo-American world in which first prevailed the idea that the marine layer levels were Abrasionsplattformen (Charles Lyell ). With this thesis, several major American researchers critically examine (Andrew Ramsay, John Wesley Powell ( 1834-1902 ), Grove Karl Gilbert ( 1843-1918 )), which again led to new theories. The first geomorphologist who dealt ( Georg von Neumayer, Alfred Hettner ) in German-speaking with the escarpments were still heavily influenced by the Anglo-American preparatory work. Albrecht Penck in 1894 coined the term cuesta landscape.
The cycle theory of William Morris Davis in the 1920s gave the entire geomorphology and hence the cuesta new impetus for research. To her, however, was criticized for not sufficiently emphasize the different rock layers (grade man). So it was eight years after the Davis'schen cycle model to the publication of the classic film stage theory by Heinrich Schmitt Henner (1887-1957), which still determined to share the understanding of shift stages. In the period after the Second World War, the cuesta research expanded under more empirically embossed approach increasingly on regions outside Europe, leading to greater consideration of climatic aspects led (eg Hans Mortensen ( 1894-1964 ), Jean Tricart ( 1920-2003 ), Julius Büdel or Ingrid dehydrator ).
This eventually led to a distinctive research dispute in the 50s - 70s of the 20th century between those who interpreted the bedding planes as " structural " areas and those who tended to favor a sculpture form. This academic dispute was also the culmination of the cuesta research. In this case, however, neither of the two camps was able to prevail in full. Since the 80s, the geomorphology tends increasingly to a procedural understanding and primarily deals "only" with selected partial aspects or processes. A holistic interpretation is almost completely faded into the background. Thus, here one encounters the fundamental dilemma of layer stage theory, which is that to this day still was no generally accepted layer stage theory in German-speaking and there.
The attempts to explain the cuesta landscapes were as always in the tension between the emphasis of exogenous (sculpture; peneplain emphasis ) and endogenous (structural ) factors. The cuesta research followed here, although the paradigms of geomorphology, has remained true to this day within which their very own dialectic. The modern geomorphology will certainly follow their development cycle to return someday to an interpretation of whole landscape complexes, whether but then let the developed individual knowledge together to form a holistic theory remains to be seen.