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Geographic Landform

一、Landform evolution and characteristics

The county is located in the hinterland of the Loess Plateau in northern Shaanxi,and for a long time, a layer of 10~30 meters thick loess has been extensively covered on the paleotopography formed by the Mesozoic strata and the Cenozoic Late Tertiary red soil layer.

Due to the large-scale vertical ups and downs of the tectonic movement in the platform area (mainly ascending), coupled with the serious destruction of natural vegetation, through a long term of water erosion and denudation of other external forces have formed ravines, vertical and horizontal ravines, deep river valleys, and beams, which results in undulating hills and gully landforms.

According to the geological age, the loess layer in this region can be divided into new loess (Malan loess in the late Pleistocene) and old loess (lishi loess in the Middle Pleistocene and Wucheng loess in the early Pleistocene). The new loess is light yellow, usually grayish yellow, loose and fragile, porous, with strong water permeability and large carbonate content, and calcareous nodules (gingerstone) are small and rare. The thickness of the new loess is small, generally 10~20 meters, and it is susceptible to water erosion (erosion, submergence) and wind erosion, forming gullies and caves. If there is an impervious layer in the lower part, it is easy to cause landslides and landslides. If there is too much water, mud flow phenomenon can occur.

Under the new loess is the old loess layer, which is generally more than tens of meters thick. Lishi loess is the main part of the plateau, beams, and ridges. Its color is yellow and reddish, its appearance is darker due to the effect of long-term weathering, and it will appear light brown when wet. There are not many pores, but denser; vertical joints are developed; water permeability is strong; common calcareous hyphae and ginger stone are often seen. The palaeosoil layer (red band) is often sandwiched in the soil layer, and there are at most more than ten layers, with each layer of about 0.5~1 meter thick, and the thickest of 2 meters. Except that it has the same geomorphic characteristics as the new loess (very strong soil erosion), the old loess is characterized by denudation, often with upright and smooth steep walls; because of the palaeosoil layer, the corrosion resistance is slightly stronger than the new loess.

There are three types of soil erosion in the loess area of the native land: water erosion, wind erosion and gravity erosion. Modern erosion of gullies and valleys--the gullies’ advancement, the valleys’ undercutting and the valley slopes’ extension are all active, which is because the loess is rich in soluble lime. So when rainwater penetrates, the lime is dissolved and lost, causing the soil to collapse and forming common karst topography such as caverns, loess plates, loess pillars, and flyovers. Generally at the edge of the loess plateau, the upper part of the ditch head, the side of the ditch where the valley slope expands more strongly, and the bottom of the branch where the ditch bed is cut more quickly, there are many caves, and sometimes bead-shaped caves are seen. Wind erosion is not very serious in local county. As for gravity denudation, the main methods include collapse, landslide and diarrhea, whose main reasons for its occurrence are the lack of vegetation, steep slope, frequent alternation of dry and wet soil layers, erosion of the bottom, groundwater activities and so on. Gravity erosion and water erosion often occur at the same time and they are interconnected.

The top of the loess plateau is often eroded into bun-shaped soil mountains, and the height of the stratum exposed is determined by the cutting of the river. The outcrop of the Dali River is generally higher, nearly 100 meters.

二、Landform type

The county belongs to the landform of the hilly and gully area of the Loess Plateau,whose characteristics are dense gully, fragmentation, undulating ridges with round tops, short ridge trabeculae, deep cuts in the ground, and obvious gully lines. Because of the damage of soil erosion for a long time, the entire county is cut into different landforms such as plateaus, beams, slopes, ridges, ditches, terraces, and streams. According to the large landform types, it can be divided into two types: hilly and gully area and Sichuan gully area.

(一) Loess beam ridge hilly area

This area includes all areas except the Dali River, the Huaining River and other river areas.

The northern beam ridge hilly area includes a vast area to the north of the central water ridge except for rivers such as the Dali River and Chabagou. It involves 17 towns, 264 village committees, with an area of 987.56 square kilometers. The altitude in the area is 1000 to 1405 meters, with a relative elevation difference of 405 meters. Its characteristics are beam hills, beams dominated, many beams and few ridges, developed gullies, the ratio of the land to the gully is 1:1, the gully density is 4.9 km/square km, the beam slope is 10~20 degrees and the slope is above 35-45 degrees. The flowing water erosion and slope erosion are serious, and landslides are common, with a soil erosion modulus of 13,400 tons/square km.

The southern beam ridge hilly area includes a vast area south of the central water ridge except for the Huaining River. It involves 9 townships, 154 village committees, with an area of 642.7 square kilometers. The area is wide and the altitude is low, generally 1000-1340.8 meters, with a relative elevation difference of 340.8 meters. Its geomorphic characteristics are many ridges and few beams, alternating between ridges and beams, presenting upper ridges and lower beams; ridges and beams undulating, small ridges, short beams and gullies are well developed. The ratio of land to gully is 4:6, the gully density is 3.7 km/square km. The beam slope is 10-25 degrees, and the valley slope is 25~45 degrees. The erosion of slopes and gullies is severe, and soil erosion is extremely serious, with a soil erosion modulus of 20,700 tons/square km.

(二) Loess plain road area

The Dali river plain road area goes across the northern mountainous area from west to east, which includes the banks of the Dali River, the Xiaoli River, Chabagou and other rivers, involving 9 towns, 99 village committees, with an area of 274 square kilometers. It has developed terraces, wide river surface, flat land and low altitude. The Dali river plain is 500~800 meters wide, and the valley is 863~1003 meters above sea level. The Xiaoli river plain is 200~500 meters wide, and the valley is 926~1022 meters above sea level. The Chabagou plain is 50~400 meters wide.

The Huaining river plain road area goes across the southern mountainous area, involving 4 townships and 33 village committees along the Huaining River, with an area of 119 square kilometers. It has developed terraces, narrow river surface, about 200~700 meters wide, less irrigated land, and the river valley is 881~1027 meters above sea level.

三、Typical landform

According to the natural environment of the landform, the physical and chemical properties of the soil, and the difference in utilization, the loess hilly and gully land types can be divided as follows:

There are few remaining plateaus in the county, distributed in Miaojiaping, Peijiawan and other townships. It covers an area of 1337.6 acres, appearing in the north-south plateau area of the watershed. The terrain is flat, but the middle is slightly depressed, with an altitude of about 1100 meters.

The plateau and beam land are divided into wide flat and narrow inclined plateau beam land, which remains very few, with an area of only 375.5 mu. It is mainly distributed in Huainingwan, Dujiawan, Miaojiaping and other townships, and appears at the upper part of hilly beam ridge, which has a flat ground and good moisture conditions, making it a good agricultural land.

There are few remaining stream land in this county, distributed in Lixiaohe, Peijiawan, Huaishucha and other townships. It covers an area of 1216.6 acres, which is a relatively low flat depression in hilly and gully land or river plateau area. The surrounding area is mostly beam ridge slope land, whose channels are connected.

The beam ridge land is distributed throughout the county, which belongs to the beam ridge land above the gully line. It is the main landform left over by erosion in the county, with an area of 1,479,144 mu, accounting for 47.1% of the county's total area. This category includes terraced land, artificial plains, gentle slopes, steep slopes, sand lump. The terraced fields are distributed on beam ridge land in all townships (towns) of the county, with an area of 336,829 mu; the artificial plains are distributed in Huainingwan, Tuoerxiang, Miaojiaping and other townships, with a small area of only 380 mu; The gentle slope land is distributed on the beam ridge land of all townships (towns) in the county, which mostly appear in the relatively gentle mouth and the upper part of the beam ridge, with an area of 116,418 mu. The soil erosion is relatively light, mainly by surface, furrow, and rill erosion. Generally, there are no eroded gullies on the surface on precipitation slopes; steep slopes are distributed in the whole county, mainly above the gully line and below the beam ridge, with a slope of 25~35 degrees, covering an area of 975,367 mu, accounting for 32.14% of the total area of the county. Due to the intensity of erosion, the cutting trenches are very dense, and large gullies appear on the lower slopes; the sandy land is distributed in the townships of Lixiaojiahe, Dianshi, Xizhuang, etc., with a small area of only 149.5 acres, which accounts for 0.01% of the total area of the county and is the leeward slope of beam ridge. The lower part of the southeast direction is due to the semi-fixed isolated sand slope and sand cave formed by wind erosion and desertification.

Gully slopes are distributed throughout the county, which are all kinds of slopes below the gully line and above the slope baseline. It covers an area of 140,1801.8 mu, accounting for 46.19% of the total area of the county. Its slope is greater than 35 degrees, which is the most serious part of soil erosion. The collapse and collapse are mainly formed because of ditch erosion. This type can be divided into five types: the sloping land is distributed below the gully line of the county, with a slope of 35~55 degrees. The soil is mostly seen in loess soil, followed by hard loess and red loess, with an area of 1143246.7 mu. This surface is very broken. There are landslides, overhangs, gullies, caves, etc.; landslides are distributed throughout the county, with an area of 35,417 mu, formed by large-scale landslides and accumulation of beam ridge slopes; earth cliffs are distributed in all townships (towns) of the county, with a slope greater than 55 degrees below the gully line and an area of 216883.9 mu, which is an area with extremely strong soil erosion. Large areas of hard loess and hard red soil are exposed, rarely covered by vegetation, vertical joints are obvious, and rock cliffs and slopes are often caused by collapses, with an area of 6254 mu, accounting for 0.2% of the total area of the county. It is the result of the continuous erosion of the ground surface and the loss of the soil parent material to expose the bedrock. The rocks are mostly red sandstone, blue sandstone, sand shale, slate, etc.

The slope land types are distributed below the slope baseline of the county and above the bottom line of the ditch, which are formed by accumulation of alluvial deposits, silt deposits, and slope deposits. According to small topographical changes and formation factors, it is divided into: ditch bed land, which is distributed throughout the county, covering an area of 9188 mu, the necessary place for running water, and often appears as a meandering terrace; ditch land, which is distributed throughout the county with an area of 40308 mu. It is located on both sides of the ditch bed or ditch, and also in the ditch palm; ditch platform, which is distributed in all townships of the county, with an area of 28803 mu. It is located on both banks of the wider main ditch and dry ditch; ditch and dam land, which is distributed in the whole county. It covers an area of 4,7717.5 mu, mostly formed by damming the dry ditch bed to intercept flood and overflowing silt; the nest land, with an area of 614.7 mu, is located at the head of Zhimaogou and is a small block dam made by artificial interception of flood and siltation land; reservoirs, with 11 large and small reservoirs and 2,993 mu of water surface.

River land types are riverbeds, floodplains and terraces formed by alluvial and proluvial surfaces below the slope foot line of the valleys of the Dali River, the Xiaoli River and the Huaining River, covering an area of 71408.8 mu. It is distributed in 11townships (towns) including Macha, Zhoujia, and Sanyanquan, Dianshi, Matigou, Shuanghuyu, Miaojiaping, Huainingwan, Peijiawan, Laojundian, Hejiaji, etc. And It has flat terrain with a slope of less than 7 degrees.

四、Mountain peaks

Within the county, there are undulating hills and overlapping mountains with 3325 large and small hills totally. Among them, there are 495 peaks with an altitude of 1,200 to 1,299 meters, 62 peaks of 1,300 to 1,399 meters, and 3 peaks of 1,400 meters. The general trend is that the mountains in the southwest are steep and the mountains in the northeast are low and gentle. The surface is all covered with loess, bare in winter and spring, with very little vegetation coverage and no bedrock exposed (exposed only in river valleys). The main peaks are briefly described as follows:

Gaobaiyan Mountain is located about 5 kilometers west of the Huaishucha Township Government Station. The mountain beam is east-west and the main peak is 1401 meters above sea level.

Nanluosi Mountain is located about 5 kilometers west of the Huaishucha Township Government Station. It stands side by side with Gaobaiyan Mountain. The beams are northwest to southeast. The main peak is 1,405 meters above sea level, which is the highest peak. It is named after the construction of Nanluo Temple. There is a "Heigelan" on the peak, that has grown for hundreds of years, which is a strange ornamental plant.

Sanhuangmiao Geta is located 4.5 kilometers southeast of Gaojiaping Township Government Station. The mountain beam is east-west. The main peak is 1,250 meters above sea level. It was named after the construction of one Sanhuang Temple in the fourth year of Chongzhen in Ming Dynasty (1681).

Five-dragon Mountain is also called Wulong Mountain, which is located four kilometers southeast of the station of Gaojiaping Township Station. The mountain is shaped like five ridges, resembling five dragons, and its main peak is 1,363 meters above sea level. There are temples on the peaks.

Zushi Mountain, also named Kongdong Mountain, is located 8 kilometers north of Li Xiaohe Township Government, which is the boundary mountain of Zizhou and Hengshan. The ridges of the mountain range from northwest to southeast, and the main peak is 1285 meters above sea level. According to legend, there was an unfathomable hole in the mountain. There lived a large python, which often harmed the villagers. Later, Zushi discovered this place, and built a temple on its cave to suppress evil, hence the name.

Xunjiata Mountain is located 7 kilometers northeast of Lixiaohe Township Government Station. The mountain beams are northwest to southeast. The main peak is 1,304 meters above sea level and is the highest mountain in the north of Zizhou County.

Lupu Mountain is located 3 kilometers northwest of the Guayuanzewan Township Government Station. The mountain beam is north-south. The main peak is 1250 meters above sea level. The Xinglong temple was built on the mountain in the third year of Chongzhen in the Ming Dynasty (1630). It is said to be presided over by Lupu monk, hence the name.

Muliansi Mountain, also named Wanniu Mountain, is located 7 kilometers west of the Sanchuankou Township Government Station. The mountain beams are northwest to southeast, and the main peak is 1259 meters above sea level. On the top of the mountain is the Mulian Temple built in the Ming Dynasty.

Niangniangmiao Mountain is located at the junction of Guayuan Zewan, Xizhuang, and Sanchuankou. The ridge of the mountain is north-south and the main peak is 1247 meters above sea level. It was named after the building of a Niangniang Temple on the mountain in the 25th year of Hongwu in Ming Dynasty (1392).

Baiquan Mountain is located 3 kilometers south of Guayuan Zewan Township Government Station. The mountain beams are north to south. The main peak is 1,247 meters above sea level, with a temple on the peak.

The Fenshuiliang is located at the junction of Majiagoucha and Shuidiwan Township. The mountain beam is northwest to southeast. The main peak is 1,305 meters above sea level, which is a famous mountain in the northwest of the county.

Heiying Mountain is located on the northern plateau, 4 kilometers southeast of Zhoujia Town. The mountain beams are northwest to southeast, with an altitude of 1,264 meters.

Gaoyuan Mountain is located 3.5 kilometers east of the Zhoujiage Township Government. The mountain beams are northwest to southeast and the main peak is 1,191 meters above sea level.

Tianping Mountain is located at the junction of Dujiawan, Miaojiaping, and Tuoerxiang. The mountain beams are north-south and the main peak is 1,263 meters above sea level. It is the most famous mountain in the east of the county.

Huangluyuan is located 4.5 kilometers west of Tuoerxiang Township Government Station. The mountain beams are northwest to southeast, and the main peak is 1,262 meters above sea level.

Houge Mountain is located 7.5 kilometers west of the Tuoerxiang Township Government Station. The mountain beam are east to west and the main peak is 1272.4 meters above sea level.

Dageta Mountain is located 2.5 kilometers southeast of Zhuanmiao Township Government Station. The mountain beams are northwest to southeast and the main peak is 1287 meters above sea level.

Heigedu Mountain, also called Leigushenyan Mountain, is located 8.2 kilometers south of Hejiaji Township Government Station and about 900 meters southwest of Leigushenyan Village. The beams are east-west and the main peak is 1,341 meters above sea level. The soil on the mountain is mostly black, hence the name.

Gaoliang Mountain is located 2 kilometers southeast of Laojundian Town The mountain beams are northwest to southeast and the main peak is 1241 meters above sea level.

Majia Mountain is located 8.5 kilometers northwest of Huainingwan Township Government Station, and is at the boundary of Zhoujiage Township. The mountain beams are northwest to southeast and the main peak is also called Yuangai, which is 1.5 kilometers south of Majiashan Village and is 1231 meters above sea level.

Jifenyan Mountain is located 8.5 kilometers north of Zizhou County. The mountain beams are east-west and the main peak is 1165 meters above sea level.