What are the geographical conditions for the Pearl River Delta to vigorously develop export-oriented agriculture?
The Pearl River in China is a delta formed by alluvial deposits in the middle of Guangdong. It consists of three small deltas: Xijiang River, Beijiang River and Pearl River Delta, covering an area of about 1. 1.3 million square kilometers. The Xijiang River and Beijiang River Delta account for110. There are more than 160 bedrock mounds in the delta, which were originally islands in shallow bay about 6000 ~ 2000 years ago. There is not much sediment in the Pearl River, and the annual total sediment is only 65438+ 100 million tons. Shallow bays with many islands are conducive to sediment stagnation, so the delta has developed rapidly in the past 2000 years. Canqiu is 300 ~ 500 meters above sea level, which often becomes a beautiful scenic spot, such as Xiqiao Mountain, Yangshan Mountain, Wugui Mountain and Yashan Mountain.
Located in the southeast of Guangdong Province, at the lower reaches of the Pearl River, adjacent to Hong Kong and Macao, across the sea from Southeast Asia, with convenient land and water transportation, it is known as the "South Gate" of China.
Formerly known as Yuejiang Plain. The Pearl River Delta for short. Located in the eastern coast of Guangdong Province, China, it is a delta complex with radial estuary, which is the general name of the large delta formed by simultaneous alluvial of Xijiang River and Beijiang River and the small delta formed by alluvial of Dongjiang River. It is an inverted triangle, with the bottom line starting from Sanshui City in the west, Guangzhou City in the east, and Shilong, with the apex at Yamenwan. The area is about 1. 1 10,000 square kilometers. Alluvium is thin, generally 20 ~ 30 meters. The ground fluctuates greatly, surrounded by hills, mountains and islands, accounting for 30% of the area. The central part is plain, distributed in southern Guangzhou, northern Zhongshan, eastern Jiangmen and western Humen. The annual sediment transport capacity of the Pearl River system is more than 80 million tons, and the delta near the estuary is still extending to the South China Sea. In the estuary area, the Pearl River Delta can extend 10 ~ 120 meters every year, which is one of the key reclamation areas in China. The delta has a subtropical climate, which is warm and humid all year round. The annual average temperature is 2 1 ~ 23℃, with the highest Leng Yue 13 ~ 15℃ and the hottest month above 28℃. There are frequent typhoons from June to 10, with concentrated rainfall and the hottest weather. The annual average precipitation exceeds1500mm. The rainy season is synchronized with the high temperature season, with fertile soil and rivers, which is beneficial to agriculture. The yield per unit area of rice is among the best in China. Tropical and subtropical fruits include litchi, citrus, banana, pineapple, longan, carambola, mango, grapefruit and lemon. Three-dimensional agricultural structures such as mulberry-based fish ponds, fruit-based fish ponds and sugarcane-based fish ponds have been developed, which has become a model of ecological agriculture in China. There are sugar, silk, food, paper, machinery, chemicals, building materials, shipbuilding and other industries, known as the pearl of the South China Sea.
At present, there are nearly 100 large waterways in the delta, and there are more smaller ports interwoven into a network. The Pearl River enters the sea through eight gates respectively. There are often residual hills at the sea, and the situation is dangerous, which is called "door". The famous ones are Humen, Modaomen and Yamen. Due to the different separation conditions of water and sediment, the sedimentation rate of each inlet is also different. The Wanqingsha between Jiaomen and Li Hongqi increased by110m annually, the lantern sand in Modaomen increased by 80 ~100m annually, and the areas around Humen and Hutiaomen were less than10m. The Pearl River Delta is located in the south subtropical zone, and local people have created management modes such as "mulberry-based fish ponds", "fruit-based fish ponds" and "sugarcane-based fish ponds", which not only make use of superior natural conditions, but also protect the agricultural ecosystem. In addition, due to the construction of dikes and the establishment of electronic irrigation and drainage systems, floods and tides have been prevented and the development of agriculture has been promoted. The Pearl River Delta is rich in rice, sugarcane, cocoon, jute, banana, pineapple, papaya, litchi, longan, citrus and lemon, and the freshwater fishery is also called developed.
geographical position
The Pearl River Delta is a tropical delta, because its geographical location is south of the Tropic of Cancer (as far as the small triangle physical geography continent is concerned), and as far as the big delta is concerned, it is also between 23 40' and 265 438+0 30' north latitude, that is, most of it belongs to the tropical range. From the climate point of view, the big delta also belongs to the tropical region (see Zhu Kezhen et al. Phenology, 1962). Landform development also has this feature, and the vegetation landscape is more influenced by it, developing into tropical monsoon rainforest vegetation. Moreover, because the northern part of the delta is the mountainous area of northern Guangdong, it plays a barrier role to the cold current from the north, so that tropical vegetation can invade the mountainous area north of the Tropic of Cancer along the valley.
The Pearl River Delta region includes Guangzhou, Shenzhen, Zhuhai, Foshan, Jiangmen, Zhongshan, Dongguan, Huizhou, Qingyuan and Zhaoqing. The whole area accounts for 23.4% of the total area of the province, and the population accounts for 31.4% of the total population of the province (1.994). In recent years, GDP has accounted for about 70% of the province's GDP. The Pearl River Delta is one of the fastest growing areas in China. With the rapid development of economy, the social development in this area presents the characteristics of high degree of rural industrialization and rapid process of urban-rural integration.
The satellite map of the Pearl River Delta shows that the Luoping Mountains are its western and northern boundaries, that is, the Xijiang River Valley is west of the Luoping Mountains, which is customarily called the western mountainous area of Guangdong. To the north of the mountain range is the Beijiang River system, or the mountainous area of northern Guangdong. Luofushan area in the east is the eastern boundary of the delta.
The Pearl River Delta is located in the southeast of Guangdong Province, downstream of the Pearl River, adjacent to Hong Kong and Macao, facing Southeast Asia across the sea, with convenient land and water transportation, and is known as the "South Gate" of China.
Geomorphological features
The tropical characteristics of the Pearl River Delta are reflected in the river network, with large water volume, small sediment concentration, many radial branches and wide and deep waterways. However, because the development history began after the Middle Pleistocene, the subsidence is not large, so the biggest difference between it and the Yangtze River and Yellow River Delta is that its formation history is short, its sedimentary thickness is small, and its speed of advancing to the bay is fast. The Pearl River Delta was formed by siltation on many rivers in Gully Bay, so the landform is called composite delta. For example, Guangzhou is known as the "Three Rivers Summary". But the area is not large, and the development potential is not as good as that of the Yangtze River Delta.
The formation of Shui Gu Bay in Guangzhou was caused by the depression between Yunfu Uplift in Guangning and Huiyang Uplift in Heyuan under the influence of the Pacific Ocean and Indian Plate. In Mesozoic, there were red basins such as Sanshui, Gui Long, Dongguan and Xinhui in the depression. Surrounded by hills formed by Paleozoic strata. It was invaded by Mesozoic granite and volcanic rocks (such as Xiqiao Mountain, a tertiary ancient volcano). After leveling at the end of Tertiary, it rose in Quaternary, that is, the quasi-plane of 1000m around the delta today. For example, at the top of Beiluoshan Mountain in Qingyuan, the hilly landform is gentle, called 12 hill, which is a good base for off-season crops. The main peaks of Luoping Mountain are mostly around 1 1,000m, such as Jilong Mountain in Gaoyao (1 1,000m), Luoda Mountain in Qingyuan (1 1,024m), Apo Mountain in Fogang (1 1,24m) and Qingyun Mountain in Xinfeng (/). The decline of the Pearl River Delta has made it a low-lying hilly and terraced area. Quaternary transgression, continental shelf descent and continental rise, so Quaternary terraces tend to tilt into the sea, which makes the basement of Shui Gu Bay have buried terraces. Delta deposition began after the Middle Pleistocene (about 40,000 years), and the hilly platform exposed to the sea became the hills on the delta plain, and the valley landforms of Danxia landform and Shimen were formed at the exposed bedrock. Platforms or terraces can reach 5 levels, with a large distribution area. Plain sediments also thicken to the sea, increasing from 25m to 60m, and the thickest of quaternary sediments in Denglongsha is 63.6m, including marine layer 2 and continental layer 1, indicating that there are two periods in the delta.