Sand Patterns near Picquerel Point 2

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Some more images showing the subtle colour transitions and delicate branching patterns that characterise the low relief natural sculptures in the fine clean sand on the shore near Picquerel Point at Grand Havre in the Channel Island of Guernsey. The dendritic patterns have been created by sea water draining down the beach as the tide recedes; and this has led to a sorting out of particles by size, weight, and colour. The darker sediments that outline and emphasise the design may be organic remnants or different darker minerals. These patterns are the best of their type that I have seen – perhaps due to the very fine sand. The patterns are so delicate they could almost be drawings.

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11 Replies to “Sand Patterns near Picquerel Point 2”

  1. A colleague of mine in work told me one time that the darker sand that you see below the surface of the sand is a harmless natural algae of some sort that darkens the colour. I can’t remember the full details but at the time it allayed concerns that I had that it might have been some sort of oil pollution.


  2. According to Peter J. Hayward in the Animals of Sandy Shores (Naturalists’ Handbooks 21 by The Richmond Publishing Co. Ltd pp20-21, the black layer beneath the yellow sand is a result of anaerobic processes by bacteria. Near the surface of sandy beaches the sand is yellow where there is sufficient oxygen in the water between the sand particles for the animals who live there, and to oxidise all the organic waste products from all the micro-organisms. Between 5 – 15cm down into the sand is a boundary where the black sand starts and the water between the sand grains there is anoxic (has no oxygen). The microfauna at this depth use anaerobic processes. The bacteria can still exist using fermentation, and other chemosynthetic process to break down organic compounds and many of them manufacture sulphate, nitrate or carbonate ions to produce hydrogen sulphide, ammonia or methane that makes an unpleasant smell. It is the hydrogen sulphide reacting with iron in the deeper sand that forms black iron sulphides. As these black coated grains from the anoxic layer are moved up to the oxygenated surface layer by burrowing animals, the black iron sulphides are converted to yellow ferric oxides.


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