地理科学 ›› 1983, Vol. 3 ›› Issue (3): 269-271,274,275.doi: 10.13249/j.cnki.sgs.1983.03.269

• 研究报导 • 上一篇    下一篇

七千年来姚江平原的演变

吴维棠   

  1. 浙江省博物馆
  • 出版日期:1983-05-20 发布日期:1983-05-20

EVOLUTION OF THE YAOJIANG PLAIN IN LAST 7000 YEARS

Wu Weitang   

  1. Zhejiang Museum
  • Online:1983-05-20 Published:1983-05-20

摘要: 姚江平原属于宁(波)—绍(兴)平原的一部分,西起曹娥江,东止于甬江,南界四明山山地,北临杭州湾。平原高程绝大部分在5米以下。但有不少孤丘和低山凸出于平原上,略排成东西两列:东列在慈溪县南,余姚县北,东西横亘;西列界于上虞与余姚两县间,南北纵列。姚江干流自西向东横贯平原南部(图1)。

Abstract: According to the origin of the Yaojiang plain, it can be divided into two parts, the southern part of the plain is an alluvial plain formed during 8000~7000 years (B.P.), and the northern part of the plain is a beach plain formed in last 1000 years The formation of Yaojiang river was not more than 5000 years. Formerly, surface water flowed together and separated into two streams in the plain; the eastern one flowed eastward into the Yaojiang river, and the western one flowed northward into the sea. Lately, the flow direction of the western stream was Changed eastward. The causes of direction Change were:First, it was acted by the difference of tidal levels between east and west, the western tidal level became higher than the eastern level in 6000~5000 years (B.P.) Second, the land developed northward and deposited higher. Third, the valley in east of He-Mu-Du became deeper in same stage, causing a difference in hydraulic force. There were repeated swamping and increase or expansion of lakes in turn for several times in the south of the plain.There were two obvious swampings of lakes, one arose in 6500~6000 years (B.P.), and the other arose in 5500~5000 years (B.P.). The most obvious increase or expansion of lakes arose in 5900~5500 years (B.P.). There were a lot of lakes in the south of the plain in historical periods, and there are not so many remained today. It is very important to reserve lakes. The plain divelopment Concerning the migration of beach line, could be divided into three sections:the middle section was developed toward the sea invariably and proceeded 15 km in last 1000 years, the east section was fairly stable and developed only a little toward the sea in last 1000 years, and the west section was changed very much during recent time.