Loess

Loess, a German term meaning "loose," is derived from wind-deposited accumulation. It was first used in 1821 in the Rhine Valley Loess.

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Define Loess Soil or What is Loess in Geography?

You can define Loess soil as a type of soil that is generated by the influence of wind. Loess has no stratifications, which is its most distinguishing feature.

Sedimentary material of the silty or loamy variety that is typically yellow or brown in colour and that is mainly deposited by the wind is known as loess. Silt-sized granules that are weakly cemented by calcium carbonate make up the bulk of loess. Vertical capillaries greatly assist in fracturing the silt and forming vertical bluffs, making it highly porous and homogeneous. 

There are several types of thick loess plain blankets, the most common of which is formed of loess packages ranging in thickness from three to 16.5 feet, each of which is interspersed with layers of sediment, sand, and similar stuff. The loess complex is made up of all of these elements. 

Sandy Loess, Clayey Loess, Loessial Sand, and Loess Loam are all regional varieties of loess that form a loess series, along with true loess. To identify between individual loess elements, workers in different areas or nations have varied interpretations of the many sediment types that compose the series.

Properties of Loess

Loess soil is homogeneous and is also highly porous. The features of loess make it to be the most fertile soil among all the other types. The major grain-size fraction of loess is from 0.02 to 0.05 mm, known as the loess fraction that includes granules of medium-grained dust. A variety of grain-size analyses show that this percentage makes up around half of the total. Nearly half of the particles are smaller than 0.005 mm, making up between 5 and 10% of the total. With increasing distance from the source of dust, the grain-size distribution in various loess zones moves toward finer grains (e.g., eastward from Sand Hills, Neb.).

As porosity declines, the moisture content of loess rises from 10% to 15%. Its porosity ranges from 50 to 55 per cent at the surface to around 10 metres below the surface (33 feet). At a depth lower than this, the grain-size distribution affects the porosity. The porosity of the loess can drop from 34% to 46% if clay is added. Sandy loess has a porosity of roughly 60%.

As porosity declines, the moisture content of loess rises from 10% to 15%. Its porosity ranges from 50 to 55 per cent at the surface to around 10 metres below the surface (33 feet). At a depth lower than this, the grain-size distribution affects the porosity. The porosity of the loess can drop from 34% to 46% if clay is added. Sandy loess has a porosity of roughly 60%.

Distribution and Classification of Loess

The distribution of Loess throughout the world is quite more as compared to many types of soil. In China along the Huang Ho River, in Inner and Central Asia, in Kazakhstan, Uzbekistan and the foreland of the Tien Shan, in Siberia along Lake Baikal and the Lena River, and vast regions in the southern catchment areas of the Ob and Yenisey rivers, the world's largest loess-covered regions are located between latitudes 55° and 24° N. Many regions in Europe, including the South Russian Plain, have an extensive, uninterrupted loess cover. 

Loess is also found in prominent spots and belts in the Danube Basin, the Rhine, the German-Polish plain, and the Paris Basin. In addition, the plains of the Platte, Mississippi, Missouri, and Ohio rivers and the Columbia Plateau in North America are covered in loess. Argentina, Uruguay, and sections of New Zealand all have "pampas loesses," or large areas of loess, between 30° and 40° S latitude.

They can be found on a wide range of relief features, including plains, river valley slopes, pediments on the forelands of mountains, and pediments. Europe, Inner Asia, and China all have loess up to 400–600 m above sea level; in the Himalayas, it can reach up to 4,000 m.

Based on physical and chemical features, the origin of loess is either completely or partially ignored in the lithological classification. In addition to loess, loessial and loess like deposits are also extremely common. Differences in the composition and qualities of silt and other components (clay, sand and lime) and in colour, porosity, strength and plasticity of loess deposits are significant.

What are Loess Rocks?

Silt-sized granules that are weakly cemented by calcium carbonate make up the bulk of loess and are known as Loess Rocks. Vertical capillaries allow the silt to fracture and form vertical bluffs, making it homogenous and highly porous.