Abstract:

Based on longtime data of base line, water depth, geological structure, satellite image and hydrology, the issue of the Bohai Sea Closing was discussed in this paper. The GPS observation results clearly show that the Bohai Sea is in the process of tectonic contraction. The geologic record and results of longterm tidal stations show that the sea level of the Bohai Sea is falling. The seismic profiles and drilling data show that the basement subsidence of the Bohai Sea basin has stopped. There are three key factors which determine the evolutionary direction of the Bohai Sea, namely the tectonic contraction, falling of sealevel and stopping of the basement subsidence of the Bohai Sea, and all these factors commonly lay the foundation for the Bohai Sea finally inevitably toward closing. The advancing of coastline of the Bohai Sea toward the sea and becoming shallow of the depth of the Bohai Sea are taken as powerful geological evidences which response geological processes of the Bohai Seas closing. The deposition of the Yellow River delta and the Liaohe River delta have been constantly carrying forward the Bohai Sea under the geological background which the Bohai Sea is destined to close, and the effect of silt creating land is very apparent, thus it becomes the main factor for the Bohai Sea fast towards closing. It is expected that the Yellow River estuary and the Liaohe River estuary will combine in the Bohai Sea in 400 years later, so the Bohai Sea will disappear; and that the Laizhou bay will be closed in 100 years later. With the Bohai Sea circulation change, more substances of the Yellow River may deposit towards the Bohai Sea, as a result, the closing rate of the Bohai Sea could also be accelerated. The remote effect of the Himalayas uplift causes tectonic shrinkage of the Bohai Sea, and a large number of deposits are carried into the Bohai Sea by Yellow River, thus fundamentally causing the closing of the Bohai Sea. As a whole, these geological effects in the short term will not change, and will even not change with human being activities.

Key words: tectonic compression, sediment filling, Bohai Sea