Natural Patterns on Rhossili Beach – Part 6

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Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

Natural patterns in the sand left by the out-going tide

You can see from this final photograph (6.11) that a vast area of several square kilometres of sand was covered in complex ripples and patterns – left by the out-going tide after a stormy night and rough seas (December 2013).

COPYRIGHT JESSICA WINDER 2014

All Rights Reserved

6 Replies to “Natural Patterns on Rhossili Beach – Part 6”

  1. This reminds me of the Sahara. When flying from Cameroon to Casablanca, I passed over an area with a seemingly endless sequence of dunes, stretching from horizon to horizon (probably somewhere in Algeria) that look like these ripples, on a larger scale. They are probably formed by a similar process.

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  2. You are probably right. Some of the same physical processes are involved whether the sand ripples are formed by water or wind, with the sand grains acting as a fluid. I have just started reading a book called “Sand” by Michael Welland (Oxford University Press ISBN 978-0-19-958818-3) which is a fascinating repository of information about all aspects of sand. I am hoping it will help me to understand what influences and creates the different sand ripple patterns on beaches – some being formed under water, some created by wind, or even a combination of the two forces.

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  3. Thank you. The patterns are fascinating, aren’t they? So many different variations depending on tides, currents and weather. I like it that at Rhossili the sand colours vary a lot – become separated out in the process to add a new dimension to the patterns.

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  4. I think it must be some kind of feedback process. There must be a stream of fluid with a constant direction. But then I think random fluctuations are amplified by feedback. Initially, probably different patterns compete, until one will prevail in each area.
    One could think of it in terms of information. In the shape of the ripples, the grains store information. This information then tells further grains where to move and where to settle, so it influences the processing of further information. I think this is a general principle of such emerging or self-organizing phenomena. You need a way to store information and this information has to influence what is going on further. Information taken from the environment, e.g. results of random fluctuations, are then amplified until the whole system has a coordinated state in which the positions of individual grains are correlated although no single grain knows anything about how to make such a structure.

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  5. That’s an interesting way to think about the phenomenon of sand movement and ripple or pattern formation. I had not thought of it that way – as if the grains themselves were storing information. I was thinking more of the physics involved – not that I know much about physics but I hope to get to grips with the physics of sand particles. There is the way that an individual grain of sand behaves when influenced by its environment and in particular the forces around it, like wind and moving water. Then there is the way the group of sand grains behaves when each grain interacts with its neighbours and also with the forces and pressures upon it. The group has its own behaviours that in turn create the patterns and ripples. It’s almost like a social interaction. There are also physical factors out-with the group, that influence shape, pattern and movement of the grains. For example, tubes made by marine polychaete worms living in seabed and seashore sediments, tubes that are made from shell fragments and sand bound together by mucus, can affect the sand ripple formation. There is a fascinating study of this occurrence in “Biogeomorphology of Coastal Seas – How benthic organisms, hydrodynamics and sediment dynamics shape tidal sand waves” by Bas W. Borsje 2012 ISBN 978-90-365-3434-5.

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