Loess Plateau

[4] The depositional setting of the Chinese Loess Plateau was shaped by the tectonic movement in the Neogene period, after which strong southeast winds caused by the East Asian Monsoon transported sediment to the plateau during the Quaternary period.

After the deposition of sediments on the plateau, they were gradually compacted to form loess under the arid climate.

Therefore, erosional features, including wind escarpments, loess vertical joints and gullies are present.

[5][7][8] In the past few decades, the environment and climate has changed, including the rainfall pattern, vegetation cover, and the natural hazards.

[9] These changes may relate to human development in the plateau; Chinese environmental officials are trying to find sustainable ways to manage the region.

[10] In the Loess Plateau, the geomorphology usually changes from rocky mountains to Alluvial plain at piedmont to river valley belt.

[4] The size of this belt depends on the amount of runoff and weathering materials from the rocky mountains.

The results show that the wind direction in winter and spring-storm events are the same as the orientation of the bedrock ridges.

[7][13] The development and size of the vertical loess joints depend on the vegetation coverage and slope.

[7] The water from rainfall and irrigation will infiltrate into the loess strata through the vertical joint surface and pore concentration zone.

[7] The joint systems in the loess strata are of different sizes, properties, periods, and origins.

In the Loess Plateau, the contribution of gully erosion on total sediment production in the hilly areas is about 60% to 90%.

[8] In conclusion, the geomorphic outline of the Loess Plateau was shaped by the tectonic movement since Neogene.

After that, because of the East Asia Monsoon in Quaternary, the loess and different erosional features started to form.

Loess is yellow eolian sediments that were transported by wind from an arid or semi-arid region during the Quaternary period.

After they deposit in arid areas and under strong chemical weathering and the process of carbonation, loess is formed.

When the monsoon wind and dust storm are blown from the northwest, it carries the loess of different sizes.

The grain size will increase in some northwest areas during glacial periods, even though the wind intensity does not change.

During glacial periods, the Siberian High is enhanced, and the winter monsoon become drier and stronger.

During Spring, many strong dust storms happen in the Loess Plateau which usually last for more than two days.

[6] High elevation:[6] According to the environmental lapse rate, the air temperature will decrease by 6 °C (11 °F) per 1,000 metres (3,300 ft).

[6] The removed materials are transported by the water and deposited in mountain foot and lowland basins.

People clear the forest to get more land for agriculture activities and use the wood for fuel and building materials.

[9] Different natural hazards connected with the Loess Plateau include dust storms, floods and droughts, locust swarms and landslides.

Dust storms can bury gigantic farmlands and affect the human respiratory system.

From 1965 to 1979, more than 1000 landslides that happened in the Loess Plateau were triggered by earthquake shocks and monsoonal summer rainfall.

[25] Soil erosion in the region is affected by many factors, including vegetation cover, precipitation, strength of winds, climate etc.

However, human activities contribute the most to soil erosion in the Loess Plateau in recent years.

When there is heavy rainfall and storms, the loess are easily washed away, which cause serious soil erosion.

Therefore, the Chinese government realized that it is critical to promote sustainable farming and soil conservation strategies in the Loess Plateau.

Geomorphology of the Loess Plateau
This figure shows the change in geomorphology in the Loess Plateau. Adapted from Dai et al.1992. [ 4 ] The geomorphology of the Loess Plateau changes from rocky mountains to alluvial plains to river valley belt. [ 4 ] This pattern keeps repeating from the Northwest to the Southeast of the Loess Plateau.
This figure shows the relationship between wind direction and orientation of the linear bedrock ridges. [ 5 ] The orientation of the bedrock ridges is parallel to the wind direction. Also, the direction of the ridges slowly rotates to the North in the central Loess Plateau.
This is the 3D model of the wind escarpment and the bedrock ridges.
Because of the tectonic movement, the Loess Plateau was uplifted. Many mountains and basins were formed. Afterward, the East Asian Monsoon was formed, so the silt sediments were transported to the Loess Plateau. The silt slowly turned into loess because of the arid climate. Finally, since the winds are strong, many erosional features were formed.
This map shows the geological development and sediments thickness in the Loess Plateau. [ 16 ] The thickness of the loess is the thickest in the Loess Plateau than the loess in other areas in China. From the scale, you can see the respected thickness of the loess in different colors. Adapted from Geomap.
This figure shows the thickness and distribution of loess in the Loess Plateau. [ 4 ] Adapted from Sun 2002. The loess near the Liupanshan is the thickest which is around 200 m to 300 m while the loess near the Yellow River is around 100 m thick.
This map shows the distribution of loess with the locations of basins and mountains. Adapted from Sun 2002. [ 6 ] Also, the direction of the prevailing winds is shown. It shows how and where the loess is transported [ 6 ] The sources of loess are the Gobi Desert and the deserts nearby. However, the loess in the desert comes from the Gobi Altay Mts, the Hangayn Mts, and the Qilian Mts.