Loess

Loess (main spelling) or Loess is a homogeneous, unlayered, light yellowish gray sediment, which consists mainly of silt. Frequently next to a certain carbonate content is considered an important criterion. Loess was predominantly deposited by the wind, but usually further modified after deposition in the soil.

Loess covers about ten percent of the earth's surface and is distributed mainly in the temperate climate zone. It was formed for the most part in the Quaternary ice ages.

Loess is the starting substrate for the arable best soils worldwide. Furthermore, researches and loess is switched fossil soils ( paleosols ) as archives for the reconstruction of Quaternary environmental changes.

• 7.1 Nature
• 7.2 Agriculture
• 7.3 hazard
• 7.4 Quaternary
• 7.5 Medicine

Word origins, pronunciation and spelling

The term " loess " first appeared in 1821 in connection with loess deposits in the Rhine Valley and in 1823 introduced by Karl Caesar von Leonhard in the geological- mineralogical literature. He's doing ( " loose" from Alemannic delete "loose" ) probably modified the vernacular expression extinguishing " loose soil ".

In the southern German -speaking loess [lo ː s] is closed with a long vowel pronounced, while in the North German pronunciation loess [ Loes ] with short open vowel is common. The Heysesche rule that the s -sound after a long vowel as ß, after a short vowel contrast as ss to write voiceless, in this case leads to no clear result. Both spellings are acceptable. Both Duden, 24th edition, as well Wahrig dictionary of the German language, 2007 edition, give loess as the main spelling and loess as a second notation.

The term is a technical term entered into many languages ​​(English loess, loess French ).

Controversy definitions

To this day, in over a hundred years the history of research on the concept loess, its origins and its properties discussed controversially. Considered simplistic, there is a contrast between the sedimentological observation, after which loess deposition of mineral dust as an Aeolian sediment, and soil science perspective, according to which the typical structural change is independent of the starting substrate, the crucial element of Lössentstehung.

In general, mineral dust was mobilized primarily in dry - cold climate conditions in sparse vegetation during the glacial periods in the temperate zone. Aggregation of minerals is often attributed to a Tundra to cold steppe climate, which also prevailed in many areas of the temperate zone during cold periods. Since the formation conditions often overlap, with many deposits both development criteria are met. Controversies arising as to the question of whether non- aeolian sediments with typical Lössgefüge or silty desert deposits may be referred to as loess.

Properties

Loess consists largely of silt. The clay content is in fresh loess highly variable, from 5 to about 20 percent, and can rise by weathering yet. Loess is mixed with strongly varying proportions of fine sand; its share of the batch averages 20 percent, but may also be higher. In sand contents greater than 50 percent, but still abundant silt is called sandy loess, which is regionally referred to as Flott sand. However, loess is considered well sorted sediment.

Mineralogical loess consists for the most part (50 to 80 percent) of quartz grains with 8 to 20 percent limestone fragments. Admixtures of iron hydroxides stain loess yellowish to yellowish - red. Other minerals, such as feldspars, volcanic glasses or mafic minerals are usually present in small amounts, but can be also regionally dominant, as in Argentina or in the North Island of New Zealand.

Loess is usually unstratified, unconsolidated and very porous. The porous structure of loess is often explained by former grass roots, which formed in the deposited mineral dust. Concretions of lime in the loess caused by dissolution and re-precipitation of the finely divided calcareous fragments and are referred to as Lösskindl or Lössmännchen. In rearrangement of loess by water, the substrate may obtain a stratification and is then called alluvial loess. In general, sediments, caused by rearrangement of loess, as well as decalcified loess called Lössderivate.

The individual particles in the loess have a predominantly polygonal shape. Hence its high stability, which favors the formation of loess walls along river banks, in ravines and the emergence of agricultural terraces.

Formation

Loess is formed when silt and fine sand are blowing in the absence of vegetation cover and (some up to several hundred kilometers of ten) deposited for a longer transport in areas with denser vegetation again. After deposition of the individual minerals are cemented by the slightly mobilized lime or clay content with each other in general. Mostly the Lössbildung is limited to the Pleistocene glacial periods. Loess can form even under hot - dry climate conditions when dust is blown from deserts and in the border areas where vegetation can flourish again, deposits.

In Central Europe, loess was formed during cold periods, hardly existed vegetation as a result of the year-round low temperatures; the foreshore areas of the glacier and the floodplains were even largely free of vegetation. The largest Lössvorkommen Central Europe are found in basins in the region of larger rivers, like the Rhine, Main and Danube. Responsible for the mobilization of mineral dust from the glacier forelands and floodplains were both the prevailing westerly winds and frequent in the glacial cold, dry katabatic winds from Alpine ice sheet and the northern ice cap. While sand from aeolian transport could travel only relatively short transport routes and is often found in the form of inland dunes in the immediate vicinity of Ausblasungsquelle, finer material was significantly more spent over a large area deposited in the basins, with the largest widths at ostexponierten slopes. In the higher altitudes of the mountains is accumulated aeolian mineral dust is an important component of periglacial layers

Loess and Loess sediments Lössderivate

Already during, but also after the deposition of loess can be rearranged by processes other than wind. Depending on the process, a distinction Kriechlöss (slightly rearranged on a slope ), Fließlöss ( rearranged by solifluction, usually contains a coarse skeleton of the pending under the loess material ), alluvial loess ( by rinsing rearranged ), Hangrutschungslöss, Infusionslöss ( rearrangement into a lake ), Kryoturbationslöss ( by freeze-thaw cycles mixed ).

Furthermore, the weathering attacks mainly the upper regions of the loess. Thus, the lime is dissolved and formed clay minerals. The result is loam. All of these variants of the loess is called Lössderivate.

As a parent term that includes both the "fresh" loess and the Lössderivate, 2002, the term Loess sediments (English " loess sediments " ) was introduced in the literature. On the somewhat awkward term " loess in the narrow sense " and " loess in the wider sense " that have been used previously, can therefore be dispensed with.

Dissemination

Loess is a very widespread and sediment - and depending on the definition - with the exception of Antarctica to every continent. About 10 percent of the land surface of the earth is covered with loess. Main distribution areas are the mid-latitudes. In the tropics and high latitudes there are only isolated Lössvorkommen. In the Lössgebieten Central Europe loess occurs with average thicknesses 3-10 m, but it can in favorable areas ( slipstream ) several tens meters are powerful. From Chinese Loess Plateau Lössmächtigkeiten are known to 400 m.

Germany

Loess areas are designated southern Germany as Gäulandschaften, in northern Germany as Börden. Popular names for loess in southwestern Germany ( Ortenau, Emperor chair) are glues or marl. However Geologically are marl clay carbonates.

The German loess areas north of the highlands are Central European loess zone, extending from Belgium to the Western Ukraine.

• North German Low Mountain Range Jülich flare and flare Zuelpicher Bay of Cologne (North Rhine -Westphalia) and in the lee of the Ville subsequent promontory
• Soester Plain and Westenhellweg (Nordrhein- Westfalen)
• Ravens Berger hills (Nordrhein- Westfalen)
• Calenberger Lößbörde in Calenberger region (Lower Saxony )
• Brunswick- Hildesheimer Borde (Lower Saxony)
• Einbeck Mark Oldendorfer Basin ( Lower Saxony)
• Dasseler Basin ( Lower Saxony)
• Magdeburg (Saxony- Anhalt)
• Mittelsächsisches Lößhügelland (Saxony )
• Upper Lusatia (Saxony )
• Lommatzscher Care ( Sachsen)
• Großenhainer Care ( Sachsen)

• Golden Mark ( calibration field )
• Warburger flange ( East Westphalia )
• Rheingau, Taunus, the foreshore and the Wetterau (Hessen)
• Limburg Basin (Hessen / Rheinland- Pfalz)
• Amöneburg Basin and Hessian Depression (Hessen)
• Thuringian Basin ( Thuringia)
• Upper Middle Rhine Valley ( Rheinland-Pfalz/Hessen )

• Mainz Basin and Rheinhessen ( Rhineland -Palatinate )
• Emperor chair ( Baden)
• Kraichgau, Filderebene in (Baden- Württemberg)
• Gaeu (Baden- Württemberg), consisting of grain, sloe, hedges and Strohgäu
• Franconian Gäulandschaften ( Gäuplatten in the main triangle and Ochsenfurter Gau and Gollachgau ), grave field
• Gäuboden or Dungau ( Lower Bavaria )

Austria

The Bavarian loess areas are continued to the east into Innviertel Austria. 90 percent of the loess deposits in Austria are in Lower Austria, especially in the wine district. The deposits in the area of ​​Krems reach thickness up to 40 m. World famous are the Lower Austrian loess for Stone Age finds, such as the Venus of Willendorf, the Venus from the Gallows or the twin tombs of Krems- Wachtberg. The Lössprofile of Paudorf, Furth Göttweig and Stillfriedplatz are known former localities of Lössforschung. In the south of Styria also find loess deposits.

Switzerland

Few areas of Switzerland were not glaciated or traversed by major river systems. Lössvorkommen found only in the far north to Basel, Baden and Schaffhausen.

Main distribution areas in Europe

• Northern France, Belgium, South, which turns into Niederrheinisches loess
• Southern Poland (Silesia, Lesser Poland ), in continuation of the Saxon Lössgebiets
• Hungary, Vojvodina (Serbia ), in continuation of the Lower Austrian Lössgebiets
• Southern Romania, Moldova
• Ukraine, southern Russia

Loess landscape in China

The most powerful Lössdecken are found in East Asia, particularly in China. The solidified fly ash from intra-Asian steppes is yellow-brown and highly nutritious. Nowhere in the world has loess deposited in larger quantities. Along the Huang He (Chinese Yellow River ), which takes its name from the transported sediments, it is available in blankets of up to 400 meters. Worldwide, no flow over a greater sediment load, there are nearly 40 kilograms per cubic meter of water. The entrained sludge is deposited in the river bed. Due to this increased sedimentation of the Yellow River his bed and must be curbed by higher and higher dikes. In Kaifeng and Zhengzhou, the water table is already ten meters above the surrounding countryside.

The loess layers in the mountains of the provinces of Henan, Shaanxi, Shanxi and Gansu are up to 300 m thick.

Loess in America

Both in North and South America, there are worldwide with the prairies or the Pampa known landscapes, which were influenced by loess. For the agriculture of the countries concerned (especially the USA and Argentina), they play a central role.

Today's meaning

Nature

For many plants and animals, loess is of great importance. For example, there is an enormous number of bee and wasp species that construct their nests in loess walls. Even birds such as swifts and bee-eaters (the latter isolated in southern Germany) nest on or in loess walls.

Agriculture

Loess areas are very fertile and are in Central Europe for Altsiedelland. The fertility stems from the small, but not too fine grain size of the rock that makes them easily accessible to the mineral wealth contained. The pore wealth of the loess, its good aeration and his good qualities as a water reservoir facilitate soil formation. In loess occur deep, easy to work and enormously powerful Cambisols, Luvisols and black earth. These soils and their distribution areas are particularly important for the agricultural economy. At higher annual rainfall may arise from loess and pale soils and Pseudogley. It is estimated that about 80 percent of the corn and grain production around the world is growing on loess.

In the reclamation of the Rhenish lignite mining area of the separately cleared down loess was heaped on the recovered agricultural land or floated in the polder method.

Loess has favored the emergence of Chinese high culture. Its properties facilitated the agriculture, because loess is not very fertile, but also to work with simple tools.

Endangering

The agricultural use and, in particular plowing destroys the soil structure in loess soils. Since it is easily washed away due to its small grain size (see Hjulström Chart ), the soil structure after destruction by erosion is at risk. Fallow or permanent cultivation of crops far have the same effect. Moreover, heavy agricultural equipment compacts the subsoil, so that water penetrates less easily and increases with the surface runoff and soil erosion.

In many places altan specified routes have cut deep into the loess and as often created Lösshohlwege in loess regions.

Quaternary

Loess provides an archive of Pleistocene climate and environmental conditions, and is explored in terms of their changes. The sequence of textural, structural and chemical changes can draw conclusions on past conditions and developments. Important is particularly paleosols. In deposited under cold, dry, sparsely vegetated ratios namely loess soil formation indicates longer periods of geomorphic stability; at higher temperatures as well as rainfall and denser vegetation, the sediment weathered steadily and differentiates itself by further soil-forming processes. After the overlap with Loess pedological characteristics are archived and can reconstruct the formation conditions. By examining many local expressions of these so-called loess - paleosol sequences can determine which regional impacts have caused global climate change.

Medicine

In the Nature Medicine loess is used as a healing earth for internal and external use. Reasons for this are its small grain size to verdankende high internal surface area and its high mineral content.

It is recommended that dissolved in heartburn and acid -related stomach disorders in water in small quantities swallow loess. Healing clay binds the excess of gastric acid and bile acids. This is to relieve the stomach discomfort and increase the protection of the lining of the stomach from aggressive substances. Also diarrheal diseases may be treated with loess.

In the intestine also harmful substances or metabolic bacteria can be bound by Healing Earth, which contributes to the general intestinal cleansing. Heilerde binds skatole, which is a toxic breakdown product of dietary protein. Also, certain protein molecules that are secreted by intestinal bacteria and the normal (physiological ) intestinal damage can be absorbed and adsorbed by healing earth. Thus, the recovery of the intestinal flora is encouraged.

Used externally relieves Heilerde acne, inflammation, skin, muscle and joint problems. In cosmetic skin care and beauty healing earth has a permanent place, as they should give the skin a fresh and beautiful appearance.