Lanzhou valley is a dimond basin striking from NW to SE,including 6 river erraces.The older the terrace,the higher it is above the river and the more splited the surface is.The lower terraces ramaining even and smooth,are main sites for city building.In the east plain,where Lanzhou city lies,the course of the Yellow River has continually moved northward in these two thousand years and enlarged the area of plain,which basically results from neotectonic movement and other natural factors,but human activeties have taken role of increasing importance.The main function of Lanzhou urban settlement is a ferry and a transport centre.Lanzhou used to be a important crossing site and post on the“silk road”,and then became a transport and trade centre in Northwest.In the middle of 17th century,Lanzhou became the capital of Gansu,a new province,and its population and area grew rapidly.But the real fast development of its urban settlement is after 1949.The developing process of Lanzhou urban settlement indicates that urban settlement is a system consisting of natural enviroment and human sociaty basedon the former.