The change of coastline in the history of China The coastline of the eastern mainland of China has been in constant movement and development since Holocene. The historical changes of each specific shore section have their own particularities. For thousands of years, the changes in mountainous and hilly coasts are not significant, while the changes in plain coasts are extremely significant because of the rich sediment in rivers.
After the transgression of the Lower Liaohe River in the north of Liaodong Bay (the Liaohe section below the confluence of the East and West Liaohe Rivers), the coastal part was submerged, and the inshore part that was not submerged formed a large swamp due to poor drainage. As far as the orientation of counties belonging to Liaodong County in the Western Han Dynasty is concerned, there are no cities in the coastal areas south of Heishan, west of Tai 'an and east of Beizhen in Liaoning Province, and it should be a large swamp beach at that time. This situation is reflected in the records of the round trip between western Liaoning and eastern Liaoning in the late Jin Dynasty and early Tang Dynasty. In the Tang Dynasty, the description of the lower reaches of the Liaohe River was that "the Liaohe River is muddy, and cars and horses can't get through", and "there is a hundred miles of rotten roads to the west of Liaodong". In the 2nd century/kloc, Xu Alchemy passed through the lower reaches of the Liaohe River, "the terrain is humble, and it is all awkward and stagnant. It was thirty-eight times a day when I drowned. It is called Liaohe River. It is more than 1,000 miles from Henan in the north and 200 miles from east to west, and Beiliao River is among them. " However, the exact location of the coastline at that time is not known now. According to the micro-geomorphological analysis and drilling data, some people think that the line from Gai County and Dashiqiao (now Yingkou County) to the northwest and through Dashaling in Niuzhuang is the ancient coastline that began to form in BC. This ancient coastline did not extend significantly for a long time. About 10 century, with the rise of Khitan, the captured Han people were used for reclamation in the Xilamulun River and Laoha River basins in the upper reaches of the West Liaohe River, and the grassland became farmland, which gradually increased the sediment concentration in the Liaohe River and made the coastal extension obvious. In the Ming Dynasty, the mouth of Liaohe River was at Liangfangkou Pass, which is now Dabaimiaozi near Yingkou. From here, the coastline goes west, about 25 kilometers south of Shaling, and reaches the vicinity of Wujiafen. Yingkou was originally a sand island outside the mouth of Liaohe River in the late Ming and early Qing Dynasties. After silting up, 19 was connected with the mainland in the twenties and thirties, and the eloquence of Liaohe extended beyond Yingkou.
The western part of Liaodong Bay is the Daling River Delta. The sediment transport capacity of Daling River is not as good as that of Liaohe River, and the delta stretches slowly, forming a shallow bay between Daling River and Liaohe Delta, and the historical change from north to the coast of Liaohe Plain is now called Panjin Bay. The swamp in the northern part of the bay has existed ever since. The mouth of Daling River in Sui Dynasty is Wanghaidun, which is the Youtunwei in Jinxian County, and the coastline is in this area. In the late Ming Dynasty, the coastline of the delta has been pushed to the first line of Ant Tun, Sihepu and Wenguan in the southeast of Jinzhou. /kloc-at the end of 0/9, according to the map, the coastline is in Tougou, Sigou, Dashagou, Yuanbaodi, Nanxiang and Langtuo.
Panjin Bay between Daling River Delta and Liaohe River Delta is gradually shrinking with the development of the two deltas. In the Ming Dynasty, the coastline extended to the vicinity of Dujiatai, and was connected with the coastline of Shuangtaizi (now Panshan County) and Wujiafen in the east. To the east of Dujiatai, to the south of Panshan County and to the west of Liaohe Delta, there are still small bays until the first half of the 20th century. During the Guangxu period of Qing Dynasty, Shuangtaizi River was excavated to discharge the flood of Liaohe River, which promoted the siltation of Panjin Bay. After 1958, the Liaohe River was cut off, the Yingkou River was diverted from the Hunhe River and the Taizi River, and all the water from the Liaohe River entered the sea from Shuangtaizi River. Panjin Bay, originally silted up into a swamp, gradually drained and turned into farmland and reed fields.
The changes of Bohai Bay coast in historical period are closely related to the Yellow River. During the Late Glaciation 8,000-5,000 years ago, glaciers melted and sea levels rose around the world. The coastline of Bohai Bay is similar to the current 4-meter contour line (Dagu Lake zero point). Since then, the climate has turned cold, the sea water has subsided, and the coastline has gradually pushed eastward. According to archaeological investigation, there are three belt-shaped ancient shell dikes on the west bank of Bohai Bay near Tianjin (see Tianjin shell dike), which are (1) shell dikes in Shantou-Lvgenghe-Mapengkou from east to west; ② Baishaling-Junliangcheng-Gu Ni-Shanggulin-Qikou shell dike; ③ Xiaowangzhuang-Jugezhuang-Shajingzi shell dike. According to C 14, the age of the third shell dike is 3,800 to 3,000 years ago, which is equivalent to the Shang Dynasty. According to archaeological data, the site of the Warring States period was found in the northern section, and the cultural relics of the Tang and Song Dynasties were found in the southern section. According to C 14, the lower layer was before 2020 100, the upper layer was before 1080 90, and the northern section was near Baishaling 1460 95. It shows that this shell dike has been formed for about 1000 years. 1 was formed after the Song Dynasty.
The extension of the coastline of Bohai Bay is closely related to the change of the position of the Yellow River entering the sea. Since the Neolithic Age, the Yellow River has been flowing into the sea from Bohai Bay for a long time. On the one hand, before the Western Han Dynasty, the vegetation cover in the middle and upper reaches was good, and there were many Tianjin branches and lakes in the lower reaches, so there was not much sediment transported to Haikou. On the other hand, there are many branches downstream, wandering between Tianjin, Huanghua, Hebei and Wudi, Shandong. Its main stream flows into the sea in Huanghua area, so there is not much sediment in Tianjin, which is suitable for forming seashells under the action of waves. After the Eastern Han Dynasty, the Yellow River changed from Lijin and Binzhou in Shandong to the sea. The sediment near Tianjin decreased obviously, and the coastline changed from muddy coast to sandy coast, forming the second berm. After that, the sediment of the Yellow River at the estuary of Shandong Province spread northward, and coastal plains accumulated outside the dike. After 1048, the Yellow River entered the sea in Tianjin for about 80 years. At that time, the Yellow River had a high sediment concentration, and a large amount of sediment was discharged into Haikou, which was not conducive to the growth of shells. 1 128 years, the Yellow River changed from Si and Huai to Hai, leaving Hebei Plain. The sediment in Bohai Bay decreased, so the third shell dike was formed, marking the coastline before the middle of19th century. On the south bank of Bohai Bay, since the Yellow River entered the sea between Binzhou and Lijin in 70 AD, the delta has developed rapidly. In the 9th century, the estuary was 70km east of Binzhou.
Lijin County is located in the Jin Dynasty, and there is a saltworks in Guo Feng Town, 35km northeast of it. /kloc-After the Yellow River captured the Huaihe River in the 0/2nd century, the original delta coast was eroded by waves and retreated. /kloc-in 0/855, the Yellow River entered the sea from Lijin, Shandong Province, and the new delta expanded rapidly, and the estuary sandbars extended to the sea at a speed of 2 ~ 3 kilometers per year. In the past hundred years, the reclamation area of the Yellow River in this area is about 2300 square kilometers. The sediment in Haikou was transported northward by the current, and a large silt beach was accumulated outside the third shell dike on the west coast of Bohai Bay.
In the 2nd-3rd century BC, the plain coast of Luanhe River Delta was located near the southern foot of Jieshi Mountain in the north of Changli County. Both Qin Huang and Hanwu climbed this mountain to see the sea. After the Eastern Han Dynasty, the Luanhe Estuary wandered back and forth in the delta, sometimes southwest and sometimes southeast, and the delta continued to extend south. In the Zhu era, the coast was already south of today's Laoting.
In the Ming Dynasty, the southwest coast was near Baigezhuang, and the southeast was 16 km south of Jieshi Mountain. /kloc-Before the 9th century, the Luanhe River Delta developed slowly. It was because the mountains in the upper reaches of Luanhe River were closed in the early Qing Dynasty. At the end of the Qing Dynasty, the ban was lifted, deforestation was serious, soil erosion was intensified, and the coastline was rapidly extended. Since 1938, the delta has been advancing at a speed of about 200 meters every year.
Today, there is a 300-kilometer-long Gongfan dike along the northern coast of northern Jiangsu, starting from Funing in the north and reaching Lvsi Town in the south. This is an important geomorphic boundary, which marks the ancient coastline for a long time in Holocene. Since the late glacial transgression, seawater has infiltrated into the northern Jiangsu plain. Under the action of waves, sediment moves laterally and accumulates into offshore sandbanks, and a belt-shaped hillside is formed along several sandbanks or berms on both sides of Gong Fan levee, which is the sandbanks in the sea at that time. Today, He Lixia Depression and Yunxi Lake used to be the scope of lagoons. The sedimentary profile shows that Xinghua area is a coastal silt layer below swamp and lake sediments (about 2 meters thick).
There are also sand dikes in the abandoned plain area on the north bank of the Yellow River, but they are not as neat as Gongfan Dike. In the historical period, there were great lakes such as Shuoxiang Lake and Sangxu Lake in the west of Dixi, which were also the remains of lagoons. /kloc-silted to the ground after 0/8th century. /kloc-Before the 8th century, Yuntai Mountain was a big island in the sea, which was called Yuzhou in ancient times.
Du Yan County in the Western Han Dynasty is located in the northeast corner of Yancheng County, which is a salt-producing area. In the Southern Song Dynasty, the sea was half a kilometer east of Yancheng County (Yu Di Jisheng). Before the Northern Song Dynasty, the Yellow River entered the sea in Bohai Bay for a long time, and there was not much sand coming from Huaihe River. Surabaya (also known as Qinghe), the main tributary of the Yellow River, is also a clear river. So at that time, the Huaihe River mouth was deep and wide, and the tidal bore could reach 10 meters. In the 8th century (Tang Dynasty), a coastal weir, also known as Changfeng weir, was built between Huai 'an and Yangzhou. It will be destroyed soon. 1 1 century, under the auspices of Fan Zhongyan, the garrison weir, which is now Fan Gongdi, was rebuilt. It can be seen that from the Western Han Dynasty to the Northern Song Dynasty, the coastline of northern Jiangsu was stable for a long time, not far to the east of Fan Gong Dike.
1 128 years, the Yellow River invaded south China, and for more than 700 years, the Yellow River seized the Huaihe River and entered the sea. A large amount of sediment poured into the Huaihe River. But in the first few centuries, the Yellow River was divided into Ying, Vortex, Sui and Si, and sediment accumulated along the way. Historically, the expansion of estuaries has not changed as fast as that of Jiangsu coast. After the middle of the 6th century (16), the whole river disappeared, and the Huaihe River entered the sea, especially in 1578, when Pan Jixun built a dam to block the mouth, there appeared a fixed channel from the border to Si and Si to Huaihe River, which is the Yellow River blocked on today's map. He adopted the policy of "attacking sand with water", and a large amount of sediment accumulated in the estuary, and the coast continued to extend outward. /kloc-At the beginning of the 6th century, the Yellow River entered the sea outside Yuntiguan (now southwest of Binhai County, Jiangsu Province). 1700 (thirty-ninth year of Qing emperor Kangxi), the estuary was outside Batan, about15km east of the stone. 17 1 1 year (the fiftieth year of Kangxi), the ferry between Yuntai Mountain and Haizhou was flat, and Yuntai Mountain was connected with the mainland. During the Yongzheng period, the estuary moved to Wangjiagang outside Batan. 1776 (forty-one years of Qianlong), dozens of kilometers of new beaches rose on both sides of the estuary. The estuary is in Sihongzi. 18 10 year (the 15th year of Jiaqing), the estuary reached Liu Hongzi again. Since the middle of19th century, the estuary has been seriously silted. Yancheng county can be taken as an example for the abandoned coastal areas of northern Jiangsu on the south bank of the Yellow River. During the Tang and Song Dynasties, the sea was less than 1 km east of the city, 15 km east of the city in the 5th century, 15 km east of the city in the early 7th century, and150 km east of the city in the middle of the 9th century. 1855, the Yellow River diverted from Shandong to the sea. Since then, the coastline of northern Jiangsu has retreated to varying degrees. At first, the abandoned Yellow River estuary shrank backwards at a rate of about 1 km per year. After entering the 20th century, it dropped below 400 meters every year, and gradually stopped after the revetment project was repaired. Only Haizhou Bay, north of Lianyungang, is still silting up.
The Yangtze River Delta at the mouth of the Yangtze River is the product of long-term interaction between the Yangtze River and the East China Sea. After glacial transgression, the delta was gradually covered by seawater, and the coastline is about 4 ~ 5 meters above sea level today. About 6000 ~ 5000 years ago, most areas of the delta became shallow seas, lagoons, swamps and coastal lowlands. The mouth of the Yangtze River is trumpet-shaped below Zhenjiang and Yangzhou, and there is a Wang Yang outside the mouth. Later, under the action of waves, the ancient sand mouth in the north of the Yangtze River and the ancient sand dike in the south of the Yangtze River gradually piled up to form the Triangle Bay.
BC 1 century, the south edge of Shazui on the north side of the Yangtze River Delta Bay was located on the south bank of Yangzhou and Taixing, and it bent northeast to Rugao and Bao Li. The front end of the sand mouth is east of Rugao. There is an ancient sandbar (Fudao Island) in the east, which divides the main flood of the Yangtze River into north and south roads. As the main flood gradually flows southward, the Jiajiang River between the sandbar and the sand mouth near the north bank is silted, and the sandbar meets the shore, forming an extension of the sand mouth. For example, after Zhou Fuhai merged with the coast, a horseshoe-shaped bay (the predecessor of Xinchuan Port) was formed. During the Six Dynasties, the northern coastline was roughly on the line from the south of Taixing and Rugao to the east of Baipu, and the front end of the sand mouth was pushed to Rudong (port opening), which was called Liaojiaokou. Nantong is still in the sea. Off the coast, Hudouzhou, 40km long from east to west and17.5km wide from north to south, rose between Nantong and Haimen today. Hudouzhou joined the shore at the end of the Tang Dynasty and formed a horseshoe-shaped bay in Yaogang today. Polygonum cornutum mouth extends all the way to the west of Sheshe. In the Tang Dynasty, Dongzhou and Buzhou rose from the coast and later merged into Dongbu. In the early years of Northern Song Dynasty, Liao Jiaokou extended to Lvsi. During the Southern Song Dynasty, the coastline was roughly in Taixing, Langshan, Renshan and Jiangjia Town. Today, the southeast of Haimen County and Qidong County has not yet become land. Since 14 and 15 centuries, the main stream of the Yangtze River has moved northward, and the land in Haimen County (now the north of Qidong County) has collapsed in a large area. Haimen County moved inward three times from Yuan Dynasty to Zhong Zheng to the 11th year of Qing Emperor Kangxi (1672). In the end, except for the corner of Lu Si, all of them collapsed into the river, and finally abandoned the county as a township and merged into Tongzhou. After Yongzheng in Qing Dynasty, it began to deposit again, forming Haimen Group Sand. During the Qianlong period, Haimen Qunsha came ashore to form today's Haimen County. During the Daoguang period, Qidong Group Sand appeared to the east of Haimen. During Guangxu period, Qidong Qunsha merged with the bank, and Liao Jiaozui moved to the vicinity of Yin and Yang. Today, the northern delta has basically taken shape. Therefore, the extension of the sand mouth on the north bank of the Yangtze River estuary is basically formed by the confluence of sandbars from northwest to southeast.
Outside the mouth of the Yangtze River in the Tang Dynasty, the eastern and western sands rose, which was the embryonic form of Chongming Island. 12 century, it evolved into Sansha, also known as Chongming Sand. Chongming town in the five dynasties. Chongming was founded in 1277. Chongming County in the Ming Dynasty was moved to its governance five times because of beach collapse. During the Qianlong period of the Qing Dynasty, Chongming sandbar merged with the surrounding Nansha and Pingyang sands to form sandbars, forming the basic outline of Chongming Island.
On the south bank of the Yangtze River estuary, under the long-term wave action, a number of northwest-southeast sandbanks, commonly known as Shen Gang, have been formed from Fushan Mountain in Changshu, Tai Fang in Taicang, Jiading, Maqiao and Fengxian New Temple in Shanghai, to Caojing Line in Jinshan and its east. There are five Shen Gang in the north of Wusong River, and the easternmost one is equivalent to Loutang, Jiading, Ma Lu and Nanxiang. There are three in the south of Wusong River, and the easternmost one is equivalent to Zhuzhai, Xinshi and Zhelin. Since 1950s, Neolithic sites have been discovered in maqiao town, Shen Gang, which shows that Shen Gang was formed 5,000 years ago. However, no cultural sites before Wei and Jin Dynasties have been found in the easternmost land east of Shen Gang, indicating that it will not be too early, about 1 century or after the 3rd century. In a word, this Shen Gang district has accumulated for about 3000 years. After the 4th century, the coast moved forward. At the beginning of the 8th century, about 20km east of Shen Gang has landed. /kloc-At the beginning of the 20th century, the coastline has reached Yuepu, Jiangwan, Beicai, Zhou Pu, Xiasha and Fengcheng to defend the seawall. In 200 years, it has advanced about 10 km. 165438+The coastline in the 1950s started from Laobaoshan in the north, crossed the middle reaches of the Yangtze River, and turned southwest between Fengcheng and Tuantuan. During the period of 150, it will be pushed eastward for 7-8km. In the 65438+70s, the coast had reached Litang, that is, the first line of Chuansha, Nanhui and Datuan, and the coast pushed eastward for 6-7 kilometers.
Since the Ming and Qing Dynasties, the coastline on the south bank of the Yangtze River estuary has been slowly lengthened. During the Wanli period, the Waihan seawall was built. In the 11th year of Qing Yongzheng (1733), Lian Zhongxiu, the magistrate of Nanhui County, was called Qin Gongtang, which is roughly the present coastline. Individual shore sections are still 2 ~ 4 kilometers away from the current coastline. From the middle of Ming dynasty to Yongzheng period, it gradually stabilized after collapse and Qianlong, but Nanhui mouth continued to extend to the sea.
Before the 4th century A.D., the coastline on the north side of Hangzhou Bay was roughly from Dajianshan to the east, passing through Ganpu to Wangpanshan, and turned northeast to connect with Zhelin and Fengxian. Today is the sea between jinshanwei and Wangpanshan, but it was a coastal plain at that time. Since 1930s, Neolithic sites and villages from the Spring and Autumn Period to the Qin and Han Dynasties have been found in the tail beach of Jinshan, Qijiadun beach and the mountainside of Dajinshan. Xu Haizhong, south of Xupu 1.5km, once exposed an ancient site in the extreme low tide of17 ~18th century, which was called the old city. According to records, it should be the former site of Haiyan County in the Eastern Han Dynasty. According to the above, we can see that this coastline is stable for a long time. Until the Eastern Jin Dynasty in the 4th century, Wangpanshan was still a coastal fortress. With the extension of the sand mouth on the south bank of the Yangtze River estuary, the south bank of Hangzhou Bay accumulates, which changes the hydrodynamic conditions of seawater and causes the north bank of Hangzhou Bay to collapse. Wang Panshan was the first to collapse into the sea. At the beginning of the Tang Dynasty, the coastline started from Ganpu in the west, passed Wanghai Town (7.5km east of Haiyan) and Ninghai Town (east of the county) in the northeast to about 5km southeast of Jinshan, and turned northeast, connecting with the coastlines of Fengxian and Zhelin South. In the late Tang Dynasty, the coastline near Jinshan collapsed seriously, and in the late Tang Dynasty and the Five Dynasties, the tide approached the foot of Jinshan. Haiyan's coastline is 2.5 kilometers east of the county seat, and Zhapu's coastline is south of Guyi City. This coastline was maintained until the early Southern Song Dynasty. After that, the coast shrank rapidly. 65438+ Jinshan began to enter the sea in the 1950s, and Ninghai Town outside Haiyan City was also swallowed up by seawater in the Yuan Dynasty. The coast is about 1 km away from Yancheng, which was only half a mile in Ming Dynasty. 15 In the 1960s, the coastline approached the south of jinshanwei, and there were few beaches. Since 1970s, seawalls have been built repeatedly, which has controlled the bank collapse and slightly enlarged the bank of the pond. Roughly the same as today.
Yaojiang Plain on the south side of Hangzhou Bay landed late. The Neolithic site discovered in Hemudu in 1970s is about 7000 ~ 6000 years ago. As far as the paleontology discovered at the same time is concerned, this area is still in the environment of water town and Zeguo. Explain the lack of land, low terrain, near the sea. Therefore, the sites in the Spring and Autumn Period and the Warring States Period are mostly distributed in the transitional zone between the plain and the foothills. The northern part of the plain later landed. The ancient seawall (Great gutang) on the north side of Linshan-Hushan (Cixi County)-Shanglin Lake was built in the Northern Song Dynasty and the Qing Dynasty (104 1 ~ 1048), and the Cixi Plain in the north was formed later. /kloc-After the 0/2nd century, the coast pushed outward a lot, rising to the north of Greater gutang (also known as Houhaitang). /kloc-imploded in the 3rd century, and collapsed to the northern foot of Xiepu, Guancheng, Hushan (Cixi), Linshan and Maigaishan in the 4th century, until the first line of Songxia Town (Song Cheng) where gutang was located. Bow to the north. Since then, it has expanded outward and built a series of earthen ponds (from Houtang to Tang Qi). We can also see the general trend of coastline development. From Houhaitang to now, the coast is about 15 km, which is the land that has risen in the past 600 years. The fourth pond was built in Chenghua period of Ming Dynasty, that is, in the middle and late period of15th century, and it is 8 kilometers from the fourth pond to the seaside. It can be seen that the external growth of16 ~18th century was slow. 19th century began to collapse again. In the 20th century, Shao began to be basically stable. In recent decades, it has gradually increased by about 6 kilometers. Since 1950s, eight ponds and nine ponds have been built.