The reasons for the formation of the tide of the Qiantang River and its characteristics

There are three reasons for the formation of the tide of the Qiantang River: the right time, the right place and the strong wind.

First of all, the time of day:

The formation of tides is mainly affected by the rotation of the earth and the gravitational pull of the sun and moon, and the greater the gravitational force, the greater the tide. Therefore, on the first and fifteenth days of each month, the gravitational pull increases, and the tides also increase. On the eighteenth day of the eighth month of the lunar calendar every year, the sun, moon and earth are almost in a straight line, and the influence of the gravitational force reaches its peak at this time, and the tide on this day is the largest.

Secondly, the location is advantageous

The shape of the Qiantang River Estuary is a trumpet-like shape, just like a bottle with a big belly and a small mouth, when the tide pours into the Qiantang River Estuary, the river channel suddenly narrows, and the huge waves suddenly narrow, and it will definitely form a turbulent tide. When the tide entering the Qiantang estuary wants to retreat, it is blocked by the huge sand barrier at the estuary, and it cannot enter or exit, and then the front wave will be blocked, and the back wave will follow, and the spectacular scene of wave after wave will be produced.

Finally, a word about the gale:

On August 18, a strong wind struck, and the wind swept up the big waves, and the big waves moved forward by the wind, how could they not be turbulent.

The above three points have created a magnificent tide of the Qiantang River, which makes people have to sigh at the magic of nature's creation.

1. Celestial time: From the 16th to the 18th day of the eighth month of the lunar calendar, the sun, the moon and the earth are almost in a straight line, so the gravitational force of the sea water on this day (the difference between the gravitational force of the moon, the sun or other celestial bodies on the earth's unit mass object and the gravitational force of the geocentric unit mass object, or the inertial centrifugal force generated by the earth's movement around the earth-moon (sun) center of mass and the resultant force of the moon (sun) gravity) is the largest.

2. Geographical advantage: It is related to the trumpet-shaped shape of the Qiantang River estuary. On the south bank of the Qiantang River, 500,000 acres of land are reclaimed like a peninsula to the east of Zheshan, blocking the mouth of the river, making the section of the Qiantang River from Zheshan to the outer 12 kilometers resembling a bottle with a big belly and a small mouth, and the tide is easy to advance and difficult to retreat.

The outer mouth of Hangzhou Bay is as wide as 100 kilometers, only a few kilometers wide to the outer 12th section, the riverbed of the eastern section of the estuary rises suddenly, the beach is high and the water is shallow, when a large amount of tide water pours in from the Qiantang estuary, because the river surface shrinks rapidly, the tide does not have time to rise evenly, and the spring has to push the back wave to push the front wave.

Layer upon layer. Secondly, it is also related to the sediment under the Qiantang River, which blocks and rubs the tide, making the front slope of the tide steeper and the speed slowing down, thus forming the back wave catching up with the front wave, and the wave on top of each other.

3. Wind: The southeast wind often blows along the coast, and the wind direction is roughly the same as the direction of the tide, which promotes the tide.

1. Hangzhou Bay outside the Qiantang River, wide on the outside and narrow on the inside, deep on the outside and shallow on the inside, is a very typical trumpet-shaped bay. The river at the mouth of the sea is 100 kilometers wide, and to the west to Pengpu, the river shrinks to 20 kilometers. When you reach the area of Yanguan Town in Haining, the river is only 3 kilometers wide.

At the beginning of the tide, the wide and deep mouth of the bay swallows a large amount of seawater at once, and because the river surface shrinks rapidly, it narrows and becomes shallow, and the tide that rises on the road does not have time to rise evenly, so the back wave pushes the front wave, and the wave is higher than the other. In the vicinity of Dajia Mountain, we encountered a huge barrage sand bar under water, and the tide swarmed up, setting off a towering and amazing huge wave, and the draft began to form a steep water wall, causing the initial tide peak.

2. The southeast wind often blows in summer and autumn along the coastal area of Zhejiang, and the wind direction is roughly the same as the direction of the tide, which promotes the tide. On the eighteenth day of the eighth month of the lunar calendar, the sun, the moon, and the earth are almost in a straight line, so the gravitational pull of the sea is the greatest on this day. Under the action of the moon's gravity, when the tide of the long drive reaches the vicinity of Yanguan in Haining, the tide head can reach more than 3 meters at a maximum of more than 3 meters, and the speed difference of 5-7 meters per second imitates the mighty upstream and advances upstream, which is like a bamboo, and it is magnificent.

Qiantang River tide form:

1. Qiantang River tide: cross tide.

2. Qiantang River tide: a first-line tide.

3. Qiantang River Tide: Turning Back Tide.

There are three reasons for the formation of the tide of the Qiantang River, the first point is that when the three points of the sun, the moon and the earth are almost in a straight line, the tide is subject to the largest gravitational force, which leads to the formation of the tide; The second point is that the trumpet-shaped topography of the Qiantang River estuary makes it easy for the tide to advance and retreat from the Zheshan Mountain of the Qiantang River; The third point is that the Qiantang River often blows southeast winds, and the direction of the wind and the direction of the tide flow are roughly the same, which encourages the tide to grasp the momentum.

In fact, the main reason for the formation of the Qiantang River is the gravitational action of celestial bodies and the centrifugal effect of the earth's rotation, and the special topography and wind effect of the bell mouth of the Qiantang River in Hangzhou Bay. The tide head of the Qiantang River can be as high as about 8 meters, and the advance speed is very fast, reaching nearly 10 meters per second.

Due to the trumpet-shaped topography of the Qiantang River, the more the estuary goes inside, the more it is bound by both sides of the river, so it leads to the accumulation of seawater, and the water flowing out of the Qiantang River is blocked by the terrain and promotes the water level, so the tide is wave after wave.

In the days of the tidal flood in Hangzhou, you can see the two wonders of morning tide and evening tide in one day. The next day, oh, the tide is usually 40 minutes later than the previous day's tide. When watching the tide, you need to pay attention to safety, and the perspective of watching the tide in places where you don't use it is also different.