These are images of a special type of wave, called a solitary wave or soliton. These waves retain their size and shape over much longer distances than the water waves that we are accustomed to seeing. Tsunami, the waves initiated by earthquakes and propagate across the Pacific are also solitons. Where most waves lose energy out the rear end, these waves hold themselves together, much like a mother duck keeping her brood collected when they try to stray. I observed these solitons in drainage channels on the beach in Santos, Brazil.
The dip of the beach was very slight over about a 600-800 foot (200-260 m) width. The tide was coming in. At every fifth or sixth wave, the wave height in the channel would allow the wave to travel forward and catch up with one or more earlier waves, apparently creating a sufficient wave height for this phenomenon to occur. The resulting wave was more long-lasting than the ones in front and behind it. They would travel up the entire channel, reflect and travel back down again, essentially, in tact.
When one of these waves would encounter another going in the opposite direction, there would be a good deal of churning of water with an impressive amount of noise. Then, the two waves would emerge from the seeming chaos and proceed in their separate directions.
A soliton in the drainage channel. Two solitions interacting.
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