问题描述：
50字内
问题解答：
To the east of Zheshan Hill on the south bank of Qiantang River, there are about
500,000 mu reclaimed-land like a peninsula to keep off the river mouth, so as to
make from the hill to the outside 12th section like a large-sized bottle with a small
mouth. It is easy for the tide to come, but difficult to ebb. Hangzhou Bay\'s width
is over 100km, but up to the outside 12th section is narrowed only several kilometers.
However, the river east part of the riverbed is sharply raised. In this way, it becomes
the riverbed high and water a little. As a great quantity from the Qiantang River mouth
is reaching, the tide cannot be raised equally due to narrowed-down river area. Then, it is
forced rear tides pushing front tides while the front tide is not fast enough, thus, one upon
another, forming the most magnificent natural phenomenon in the world.
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