The Qiantang River in China is famous for a unique natural phenomenon, a wave-like tide that was first observed in 2021 and is called the fish scale tide.
The mouth of the Qiantang River in Zhejiang Province has long been known as the site of the strongest tides in the world. At times, they can reach heights of up to 9 meters, meaning that this area frequently witnesses large waves moving upstream against the normal current. However, in 2021, during a scientific expedition, researchers discovered another fascinating natural phenomenon that occurs only at this river mouth. Under certain conditions, the tide appears in spiral bursts resembling fish scales on the surface of the water. This phenomenon is known as the 'fish scale tide'.
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Because this unusual type of tide has only been observed in recent years, the exact reasons for its appearance are clearly still being debated. Different sources offer various causes for the formation of the fish scale tide. For example, FyFluidDyamics believes that this phenomenon is the result of a combination of factors.
Nicole Sharp wrote: “This area is also known for its swirling currents, meaning that the tide does not simply move inland and then smoothly change direction.” “Instead, the swirling field can change the direction of the flow during the tidal cycle without altering the speed. All in all, this makes the Qiantang River area perfect for waves colliding at oblique angles, similar to a cross sea. Two sets of tidal waves are colliding at an angle, creating some harsh conditions."
According to INF News, which looks like a translation from a Chinese website, astronomy, topography, and wind direction are the primary factors contributing to the fish scale tide. Clearly, the moon and the sun play significant roles in this phenomenon, as does the shape of the river mouth – very narrow at the river mouth but wide where it meets the sea.
Whatever the precise necessary conditions for the formation of the fish scale tide may be, one thing is certain – they rarely occur simultaneously, making this phenomenon very rare.
The mouth of the Qiantang River in Zhejiang Province has long been known as the site of the strongest tides in the world. At times, they can reach heights of up to 9 meters, meaning that this area frequently witnesses large waves moving upstream against the normal current. However, in 2021, during a scientific expedition, researchers discovered another fascinating natural phenomenon that occurs only at this river mouth. Under certain conditions, the tide appears in spiral bursts resembling fish scales on the surface of the water. This phenomenon is known as the 'fish scale tide'.
View attachment 658
Because this unusual type of tide has only been observed in recent years, the exact reasons for its appearance are clearly still being debated. Different sources offer various causes for the formation of the fish scale tide. For example, FyFluidDyamics believes that this phenomenon is the result of a combination of factors.
Nicole Sharp wrote: “This area is also known for its swirling currents, meaning that the tide does not simply move inland and then smoothly change direction.” “Instead, the swirling field can change the direction of the flow during the tidal cycle without altering the speed. All in all, this makes the Qiantang River area perfect for waves colliding at oblique angles, similar to a cross sea. Two sets of tidal waves are colliding at an angle, creating some harsh conditions."
According to INF News, which looks like a translation from a Chinese website, astronomy, topography, and wind direction are the primary factors contributing to the fish scale tide. Clearly, the moon and the sun play significant roles in this phenomenon, as does the shape of the river mouth – very narrow at the river mouth but wide where it meets the sea.
Whatever the precise necessary conditions for the formation of the fish scale tide may be, one thing is certain – they rarely occur simultaneously, making this phenomenon very rare.
