The North River drainage forms on the basis of that the Yian Mountain and Himalayan movement result in distribution of tectonoclastic zones and weak rocks as well as sequence of height of redstoene basin and by means of that flows in original six biger pieces of isolated redstone basins join progressively by the action of river piracy. It is main that the earth’s crust uplifts spasmodically in the early

middle period since a million years. late. The North River Drainage forms many steps of stream terrace. In the late period

the two structure zones of Yao Mountain and the Sanlian——Sannan move obviously

fall of the crust is prevailing on vast areas

moreover

sea level varies

the Yuantan Stream is early formed at middle part of the North River Drainage

the pearl River Delta is late formed at the south part

along this drainage from the north to the south the finst step of river terrace deforms and forms into a terrace

a semi——buried berraee and a buried terrace