The shore beneath the new sea wall in Lyme Regis looks very different now the old breakwaters or groynes have been removed. You can still see the linear concrete footings of the old wood and iron structures but most of the pebbles and cobbles that used to accumulate between the walls are now absent (at least for the moment). A bare rock pavement is revealed, comprising a series of steps representing the strata and colonised by seaweeds. Rippled sand sometimes deposits in the valleys between the rock ledges.
On many sandy beaches along the Queensland coast of eastern Australia there are millions of small sandy balls. Each one is just a few millimetres across. They can form extensive mats or patterns as they cover the shore at low tide. There were many decorating the sand at Cape Tribulation when I visited in 2011. Closer inspection reveals small holes in the sand, usually at the centre of radiating lines of balls. These balls are the result of the feeding activities of small sandy coloured crabs that are themselves rarely seen. The holes are their burrows. They are the “Sand Bubbler” crabs belonging to the genus Scopimera, often S. inflata. The balls are created as the crab feeds on the organic matter attached to the sand grains on the surface around its burrow, and rolls up the cleaned grains into balls before moving on to the next spot.
The patterns vary according to the moisture level of the sand and its organic content, as well as the species concerned, I would imagine. I’ll post some more pictures later showing an interesting variation on the sand ball patterns from the other end of Cape Tribulation beach.
After the beach boulders and scattered rusty metal debris, there is sequence of flat rock platforms exposed by the retreating water. They are riddled with holes made by the boring bivalves known as piddocks, some burrows just have empty shells in them but others are still occupied by the living molluscs that squirt water a foot or more into the air at frequent intervals. A velvet swimming crab mooches around the edges of the platforms, and sand tube and mud tube dwelling worms abound on all the surfaces.
I discovered an interesting stretch of shoreline when I visited Lyme Regis yesterday. The cliff location is known as The Spittles and it is situated immediately east of the new sea wall. The tide was going out but not as far as in March 2010. Enough to disclose an array of boulders with scattered fossils, broken coloured glass, and rusting metal. The man-made junk resulted from a major landslide in 2008 when the contents of an old town rubbish tip (which had been in existence from 1920 to 1973) cascaded shore-wards with the rocks and mud. The junk continues to wear out of the cliff face to the present time.
There are some interesting items to be found. The rusting metal components, often with remnants of paint, provide intriguing contrasts with the natural environment in which they are lodged. There is a striking similarity between the metal colours and textures and those of the dead and dying autumnal colours of seaweed. As the water receded, it left intricate patterns in the sand around the rocks and even in fine sediments of smoother rock surfaces.
A wide and shallow river flows over the sandy beach at Ventry Bay on the Dingle Peninsula in Ireland. I do not know its name. Characteristic ripple marks are made in the wet sand around the margins of its wandering channels, showing the influence of the freshwater currents modified by the sea water tides. As you walk away from the fast flowing water, the overlapping ‘leaf’ patterns made by the river currents gradually transition into the parallel ridges of wave-induced ripples that are more typical of the intertidal shore .
Images of patterns on the beach caused by wave action winnowing out lighter black sediments from the heavier yellow sand grains have been shown in earlier posts. Here are three microphotographs of the black sediments from a small sample that I scooped up on the shore at the time. Sorry there is no scale because I haven’t fathomed out how to include one in the images yet.
Hopefully these shots are clear enough to show that the numerous black particles are small fragments of waterlogged wood; shiny hard pieces of coal (coal dust); a few large pale seeds not yet identified; minute fragmented seashells such as mussels; and many white slender organic objects which I think are small fish rib bones but could be or include heart urchin spines. It was these bones that gave the dried sample in the petri dish an almost fibrous appearance. I am going to see if I can find someone from the world of archaeology who would be familiar with the analysis of this type of material – to see if I can get some more specific information about these black sediments from the beach at Rhossili in Gower.
Patterned Sand 8 – 14: Naturally formed patterns of black sediment on yellow sand were photographed on the beach at Rhossili Bay, Gower, in April 2017. The black sediments were mainly composed of minute pieces of rotten wood, coal dust, and miniscule fish bones, with a small proportion of seeds. The images have been digitally colour-enhanced to emphasise the patterns of this natural abstract art.