Colluvium

Colluvium (Latin: the interaction Geschwemmte ) is the name given to a usually several tens of centimeters thick layer of unconsolidated sediments, consisting mainly arise through alluvial soil material rearranged or other mostly loamy or sandy unconsolidated sediments. Younger colluvium are often humos, but this is not necessarily a feature. In colluvium, a new soil development use ( Kolluvisol ).

Term containment

Under colluvial sediments in the German speaking basically the result of anthropogenically induced soil erosion understood by flowing water and partly by Wind transport of snow. In Anglo-American countries, the term colluvium is available for all types of slope sediments, which may also be glacial origin. A Holocene colluvium, that is, a colluvium that has arisen under the influence of man, is called Holocene colluvium. To better distinguish the educational processes relocated material is referred to as Äolium by wind.

Formation

Soil erosion is mainly on unprotected soil surfaces and in the absence of growth. This is, for example, the case when fields are just too long. Therefore, the Kulluvienbildung is often reinforced by agriculture. Deep plowing, plowing in the direction of the fall line and other types of tillage erosion -promoting effect. You can have damaging effects on entire landscapes strongly influenced by loss of humus and Sedimentabtrag. By running water ( rainfall ), the soil material is removed and gravity downslope shifts following. A fading gradient it is sorted according to the grain size redeposited. Coarser particles reach even at higher flow rate, ie earlier, finer later at low transport velocity for deposition. The fine material often reaches streams, ditches, or in lakes, where it is deposited or transported. Also complete soil aggregates ( mixtures of grain sizes ) can be shifted colluvial. Thus, the sorting effect is greatly attenuated.

Historic and prehistoric colluvia

Often have deposited one above the other numerous colluvium in the course of landscape development. They are thus relics of human habitation and partly contain archaeological finds or Gazette former soil-forming processes. These deposits can be interpreted as geoarchives history of the landscape and used their analysis to the reconstruction of past landscape conditions.

Occurrence

Colluvial sediments are common in central Europe due to the climate and the long history of use since Neolithic times. So colluvia found in almost all currently or formerly used by agricultural areas, but particularly in the Altsiedelräumen so in the Eifel and Moselle area, Kraichgau, in the Black Forest and the Swabian Alb.

In highly structured landscapes (eg in Jungmoränengebiet to the rim to the Oder ) are often several meters to meet powerful colluvium, the witness earlier erosion caused by heavy rainfall events. A well-studied example is the Biesdorfer throats at Wriezen on the edge of Oderbruchs. The 5 m deep and 50 m long canyon is not older than the trees, and accordingly their young alluvial deposits downstream.