Why does the Qiantang River tide happen?

Tides are caused by the attraction of the moon and sun to the seawater on the earth's surface. Around the first day and the fifteenth day of the lunar month, the sun, moon and the earth are arranged in a straight line, and the attraction of the sun and the moon is combined to attract the sea water on the earth's surface, so the tides on the first and fifteenth days of each month are relatively large. Especially around the Mid-Autumn Festival, it is the time of the year when the earth is closest to the sun, so the autumn tide around the 15th day of the eighth month of the lunar calendar is the largest of the year.

Mainly because of the terrain.

The main reasons for the formation of the Qiantang River tide:

The formation of the tide of the Qiantang River is caused by the centrifugal action of the gravitational force of celestial bodies and the rotation of the earth, coupled with the special topography of the Qiantang River.

The Hangzhou Bay where the Qiantang River enters the sea is trumpet-shaped, with a big mouth and a small belly, so when a large amount of blanching water is drunk, the tide head will be hindered, and the tide behind it will swell very quickly, so there will be a thrilling and spectacular scene of the big tide.

According to the research of scientists, the generation of the tide of the Qiantang River and the speed of the water flow and the speed ratio of the tide wave are also related to a certain extent, when the speed of the water flow and the speed of the tide wave are about the same, it is more conducive to the generation of the tide, but the difference between the two is relatively far, even if the terrain is better, it is difficult to form a tide, that is, all kinds of reasons together can appear the tide of the Qiantang River that we see now.

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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 typical trumpet-shaped bay. When the tide rises, the wide and deep mouth swallows a large amount of seawater, because the river surface shrinks rapidly and narrows and becomes shallow, the upwelling tide does not have time to rise evenly, to the vicinity of Dajia Mountain, and encounters the underwater barrage sand bar, the tide forms a steep water strength, resulting in the initial tide peak. Southeasterly winds often blow along the coast of Zhejiang in summer, which contributes to 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, and the gravitational pull of the sea is the greatest. Under the influence of the moon's gravity, the long incoming tide advances upstream at a speed of 5-7 meters per year, forming the great tide we see.

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The formation of the Qiantang River tide is caused by the centrifugal action of celestial gravity and the rotation of the earth, coupled with the special topography of the Qiantang River horn mouth in Hangzhou Bay. The tide of the Qiantang River is a natural wonder of the world, and the tide of the Qiantang River is the largest on the eighteenth day of the eighth month of the lunar calendar every year.

Qiantang tide refers to the tidal phenomenon that occurs in the Qiantang River basin and causes periodic fluctuations in the ocean surface due to the gravitational force of the moon and the sun. The tide of the Qiantang River is a natural wonder of the world, which is caused by the centrifugal action of celestial gravity and the rotation of the earth, coupled with the special topography of the horn mouth of Hangzhou Bay.

First of all, it is related to the shape of Hangzhou Bay, where the Qiantang River flows into the sea, as well as its special topography. Hangzhou Bay is trumpet-shaped, with a large mouth and a small belly. The channel of the Qiantang River narrows and rises sharply from the west of Luopu, resulting in a sudden reduction of the capacity of the riverbed, a large amount of tide water is crowded into the shallow river, the tide head is obstructed, and the tide behind it advances rapidly, forcing the tide head to stand steeply, break up, and roar, and there is a thrilling and spectacular scene.

However, the river estuary is a lot of trumpet-shaped, but the estuary that can form a surge is only a few, the Qiantang tide can be honored to be included in this few, scientists believe that the generation of the tide is also related to the speed of the water flow in the river and the speed ratio of the tide wave, if the speed of the two is the same or similar, evenly matched, it is conducive to the generation of the tide, if the speed of the two is very far apart, although there is a trumpet-shaped estuary, can not form the tide.

Hangzhou Bay is located in the place where the Pacific tidal wave rushes directly to the east, and it is also the direction with the largest tidal range on the west coast of the East China Sea. Therefore, various reasons came together to contribute to the phenomenon of the tide of the Qiantang River. On the eighteenth day of August of the lunar calendar every year, the tide of the Qianjiang River is the largest.

When the tide comes, the sound is like thunder, and the mountains and seas are overwhelming, which is spectacular.

The reason for the formation of the tide of the Qiantang River is that it requires favorable time, location and suitable wind conditions.

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 on 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 on the earth's centroid (sun), or the resultant force of the inertial centrifugal force generated by the earth's movement around the earth-moon (sun) center of mass and the gravitational force of the moon (sun) megaloca) is the largest.

Geographical advantage: It is related to the trumpet-shaped shape of the Qiantang River estuary. Nearly 500,000 acres of reclamation land in the east of Zheshan on the south bank of the Qiantang River block the estuary like a peninsula, so that the section of the Qiantang River from Zheshan to the outer 12 kilometers resembles the bottle clan branch Chazi with a big belly and a small mouth, the tide is easy to advance and difficult to retreat, the outer mouth of Hangzhou Bay is as wide as 100 kilometers, and the outer 12 sections are only a few kilometers wide, the riverbed in 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, so it has to push the back wave to 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.

Winds: Southeasterly winds often blow along the coast, and the direction of the wind is roughly the same as the direction of the tide, which contributes to the tide.

The reasons for the formation of the tide of the Qiantang River are:

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.

When the tide rises, the wide and deep mouth of the bay swallows a large amount of seawater at once, because the river surface is smooth and shrinks and narrows and becomes shallow, the tide that rises on the road does not have time to rise evenly, so the back wave pushes the front wave, and one wave is higher than the other. To the vicinity of Dajiashan Xinyu, and encounter a huge underwater barrage sand bar, the tide rushes up, sets off a towering and amazing huge wave, forms a steep water wall, and causes the initial tide peak. Wow.

2. The southeast wind often blows in the coastal area of Zhejiang in summer and autumn, 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 reaches the vicinity of Yanguan in Haining, the tide head can reach up to more than 3 meters, and it advances upstream at a speed of 5-7 meters per second.

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.

1. The tide of the Qiantang River.

Of course, the reason for the formation is also inseparable from the movement of celestial bodies, from the 16th to the 18th of the eighth month of the lunar calendar, the sun and the moon.

The earth is almost in a straight line, so the gravitational pull of the sea water and the gravitational force caused by the centrifugal movement of the moon are the largest, and the deflection angle and rotation motion of the earth itself cause the sea water to rise and tide.

The phenomenon is even more pronounced.

2. Nearly 500,000 acres of reclamation land east of the south bank of the Qiantang River block the river mouth like a peninsula, making the Qiantang River resemble a bottle with a big belly and a small mouth, and the tide is easy to advance and difficult to retreat.

Push the front waves, layer upon layer, forming a tidal surge.

3. The Qiantang River is located in Hangzhou Bay, which is located in the place where the Pacific tidal wave rushes directly to the east, and is the direction with the largest tidal range on the west coast of the East China Sea. Therefore, various reasons came together to contribute to the tide of the Qiantang River.

Classification of the tide of the Qiantang River.

1. Cross tide (also known as cross tide).

In Dingqiao Town, Haining City, 55 kilometers away from Hangzhou Bay, there is a place called the big gap, which is an excellent place for the cross tide. Due to the long-term sediment accumulation, a sandbar is formed in the middle of the river, and the tide wave from Hangzhou Bay is divided into two streams, namely the east tide and the south tide.

At the moment when the two tides collide, a column of water is stirred, several feet high, and the waves splash and are thrilling. When the water column fell back to the river, the two tide heads were already in the shape of a cross on the river, and they quickly rushed westward. At the same time, the intersection quickly shifted northward like an avalanche, crashing into the straight pond, causing a huge splash and falling on the top of the pond.

2. A line of tide.

After seeing the cross tide of the big gap, it is recommended that you drive to Yanguan quickly and wait for the first line of tide. Before seeing the shadow of the tide, I heard the sound of the tide first. There was a loud rumbling sound in my ears, and the river was still calm.

The sound became louder and louder, like beating the drums of war on all sides, deafening. In the distance, a white line appeared on the foggy river surface, which quickly moved westward, just like "practicing the Hengjiang River, and raising the white rainbow on the flat sand".

Closer, the white line becomes a wall of water, gradually rising, "the tide is a little higher, and the mountains are crossed in the waves". With the rapid advancement of a white wall, the surging tide came in front of him, with the momentum of thousands of horses galloping, the power of thunder, unstoppable.

The first-line tide is not only for salt officials. Where the river road is straight, there is no place in Shazhou, the tide is in a line, but it is not as good as Yanguan. The reason is that not far after the salt official position and the width of the river trough shrink sharply upstream, the east and south tides meet just into a straight line, the tide energy is concentrated, and the tide head is particularly high, usually 1-2 meters, sometimes up to more than 3 meters.

The momentum is magnificent, and the tide scene is spectacular.