Geographical environment of Yangshan county

Yangshan County is located at the junction of the Guangxi-Hunan-Jiangxi-Guangdong fold belt and the Guangxi-Guangdong uplift. The stratum is well developed and the lithology changes greatly; Yanshanian magmatism was extensive and intense; Various tectonic systems are complicated.

Before ancient times, Yangshan still belonged to the sea. About 400 million years ago, with the crustal changes, the Nanling mountain system began to take shape, forming the uplift belt in northern Guangdong. About 200 million years ago, the limestone belt in Yang Lian was formed, and most of Yangshan County was in this belt. About 654.38+0.5 billion years ago, Yanshan movement caused a fold and fracture system, accompanied by granite intrusion. About 50 million years ago, Himalayan movement formed fault blocks in the north, west and south of the county seat. The crustal movement 3 million years ago formed the undulating terrain of Quaternary.

floor

The strata in Yangshan County are widely distributed, including Cambrian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Lower Tertiary Danxia Formation and Quaternary.

intrusive rock

The intrusive rocks in Yangshan county are relatively developed, mainly concentrated in the northeast and southwest. Magmatic activity develops with Yanshan tectonic cycle and can be divided into three main intrusion periods. * * * Rock mass 10, of which Dadongshan rock mass and Yang Lian rock mass are the largest, and the rest are small rock masses near the large rock mass. They have the occurrence of bedrock or rock strain and are basically composed of granite.

structure

Yangshan county has a well-developed geological structure. According to geomechanics, multiple tectonic systems work together here to form a complex tectonic network. The east-west structural belt is represented by Dadongshan rock mass and Yang Lian rock mass, which are two secondary belts of Nanling banded structure. The Cathaysian structure in Yangshan County is characterized by the formation of a group of NE-trending folds and faults, which are exposed in the northeast of the county. The Neocathaysian tectonic system is well developed, represented by the western and central wings of the county, and exposed to the southeast of the county. Faults in Yang Lian rock mass are prominent in the N-S structure, and some N-S folds are exposed in the south of the county. Yangshan county has a complex terrain. The overall terrain is high in the south and steep in the north, with monoclinic mountains irregularly inclined from both ends to the hinterland, forming a boat-shaped landform with a low middle and high sides. Mountains account for about 90% of the county's total area, and basins and alluvial plains account for about 10%.

hilly area

1. Northeast Mountain

Dadong Mountain Range and Tianjing Mountain Range are in the northeast, with an altitude of 1000 ~ 1500m. The mountain is steep, the north slope is steep and complete, and the south slope is slowly broken. It is an asymmetric mountain with steep north and gentle south. Mengkeng Stone (also known as Shikenggan) is at an altitude of1902m, located at the junction of Yangshan, Ruyuan and Yizhang counties in Hunan Province, and is the highest peak in Guangdong Province.

2. Southwest mountainous areas

It is a branch of the Lingnan branch of Monkey Mountain, which extends to the southwest of the county seat through Liannan. The mountain folds are clear, and the axial structure is not anticline. It is mostly composed of gravel and shale, and the mountains are steep. The mountains above 1000 meters above sea level include Ishikawa Peak, Guanyin Peak, Leigong Ball and Wushan Mountain.

3. Southeast limestone mountain area

As a typical karst landform, the surface runoff is small and there are many underground rivers. The situation of "only smelling the sound of running water, not seeing the river" is more prominent. Lots of Dou Lin, sinkholes, caves, etc. It can be seen on the surface that the residual part of limestone erosion forms peaks (solitary peaks or peaks), and strange rocks, such as golden roosters and tigers and leopards, lie on various roads.

Basins and alluvial plains

1. basin

The area from the south of Taiping to Yangmei is a red rock series basin, with a small area and strip distribution, which is Danxia landform formed by red sandstone.

2. Plain

Lianjiang runs through the middle of the county from northwest to southeast, and Dongguan Water, Fucun River, Lingbei Water, Weighing River, Huangpi River, Qigong Water, Shahe River and Miaogongkeng flow into Lianjiang. These rivers form small alluvial plains along their banks, with low terrain and undulating mountains. In addition, Huangpi in the north, Yangcheng in the south, Lingbei in the east and Xiaojiang in the west are the valley plains. At an altitude of 100~800 meters, there are valley plains of different sizes, such as Xiling, Shuidou Mountain, Ye Guang Depression, Monkey Mountain, Dabeiding, Plough, Jinxingding, Gangqing and Gao Feng.

3. Mountain peak

There are 65,438+050 peaks with an altitude of 65,438+0,000 meters in the county, mainly distributed in Tianjing Mountain and Dadongshan Mountain, with a small number of Lu 'an Mountain, Martin Mountain, Guanyin Mountain and Wushan Mountain. Among them, there are 18 peaks with an altitude of1.500m, which are mainly distributed in Tianjing Mountain and Dadong Mountain in the north. Yangshan County is located in the north of the Tropic of Cancer, and belongs to the monsoon climate zone of transition from south subtropical zone to middle subtropical zone. Its characteristics: hot weather, short summer, rain and heat in the same season; Spring is mild and humid, summer is hot and rainy, autumn is cool and dry, winter is cold and rainy.

Climatic characteristics

According to the standard that the monthly average temperature in spring and autumn is 14℃ ~ 24℃, lower than 14℃ in winter and higher than 24℃ in summer, Yangshan County is in March ~ April in spring, May ~ September in summer and10 ~/kloc-0 in autumn.

In spring, the climate is mild, wet and rainy, the weather is changeable, and there are many cold and rainy days. Due to the alternation of cold and warm weather, Nanling static front often occurs, which makes the county town often have low temperature and rainy weather, humid air and insufficient sunshine, which affects spring sowing. The average seasonal temperature in plain area is 17℃ ~ 18℃, and that in mountainous area is 14℃ ~ 16℃. The seasonal rainfall is 350 ~ 400 mm, accounting for 265,438+0% of the annual rainfall; The total sunshine hours are not 127.2 hours, and the sunshine percentage is 17%.

It is very hot in summer, and it often thunders and rains. There are many rainstorms in the early stage, and there are often floods, which is called flood season; In the later period, there is plenty of sunshine and frequent drought, which is called drought period. Since the beginning of May, the tropical ocean wind blowing from the south has intensified and the temperature has risen sharply. The average seasonal temperature in plain area is 26℃ ~ 27℃, and that in mountainous area is 22℃ ~ 24℃. The hottest July, followed by August, is often controlled by subtropical high, and the weather is sultry, with the highest temperature above 37℃ and the extreme highest temperature of 39.9℃. Monsoon rainfall in May and June is prone to floods, and typhoon rainfall is dominant after July, which is beneficial to crop growth. The seasonal rainfall is1100 ~1200mm, accounting for 61%of the annual rainfall; The total sunshine hours are 833 hours, and the sunshine percentage is 52.8%.

Autumn is crisp. Affected by the dry cold air in the north, the weather turned cold, the monthly average temperature dropped below 24℃, the temperature difference between day and night was large, and it was dry and rainy. 1 1 There are often strong cold air attacks in the later period, and sometimes the first frost appears. The average seasonal temperature in plain area 19.5℃ ~ 20℃, the average seasonal temperature in mountain area 16℃ ~ 17℃, and the extreme minimum temperature 1 1.6℃. The seasonal rainfall is 120 ~ 140mm, accounting for 7% of the annual rainfall. There are many sunny days, the total sunshine hours are 3 16 hours, and the sunshine percentage is 47%.

Winter is cold, with little rain, frequent frost and occasional snow and ice, which is the coldest season in the whole year. Due to the control of the cold air mass in the Arctic continent, the temperature is low. The seasonal average temperature11℃ ~11.5℃ is lower than 10℃ in mountainous areas. The coldest month is 65438+ 10, and the average temperature is 6℃ ~ 10℃. Average last frost date; Valley plain February 8, mountain area after late February. The average frost day is 8.7 days, which is more than that in mountainous areas 12 days. The average snowy day is 3.4 days, and it is more than 5 days in mountainous areas. The seasonal rainfall is 180 ~ 200mm, accounting for 10% of the annual rainfall. The total sunshine hours are 300 hours, and the sunshine percentage is 30%.