The rock ledges below the new sea wall at Church Cliffs in Lyme Regis, Dorset, are the upper strata of the Blue Lias limestone. The natural limestone ledges and the smooth artificial substrate of the concrete sea wall, provide a home for numerous seashore creatures like limpets, winkles, and top shells as well as many commonly attached red, green and brown seaweeds, and encrusting calcareous algae (pink Lithamnion). The brown substance sticking to a lot of limpet shells is also an encrusting seaweed (probably Brown Limpet Paint Ralfsia verrucosa).
Multitudes of small holes penetrating the rocks are the often-occupied burrows of small marine polychaete worms like the Polydora species. Occasional drifts of sandy ripples coating the stone are punctured by largish round holes where bivalved burrowing piddocks living in the rocks below have squirted jets of water from their exhalent siphons and cleared the sand away.
It is interesting to see that the seashore life is equally at home on the old concrete footings from the defunct breakwaters as it is on the limestone.
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.
The main sea defence structure at Church Cliff in Lyme Regis back in 2010 and 2011 was a concrete sea wall. This was built into the base of a cliff that is made of soft slipping strata. It was from the sea wall that the iron and wood breakwaters jutted out at right angles to deflect the impact of the sea. The concrete wall in part held back the cliff and in part prevented undercutting by the waves. Over time the wall had become stained by run-off from above and by lichen and bacterial deposits to form interesting striped patterns with subtle variations like an almost monochromatic natural abstract art along the length of the wall. This wall has since been replaced by a much stronger structure, along with the demolition of the breakwaters.
The corroding ironwork on the now defunct breakwaters at Church Cliff in Lyme Regis revealed fascinating patterns and textures when viewed in close-up. These macro photographs show some of the wonderful details and colours. I only have seen similar rusting seaside ironwork before on the pier structure at Weymouth.
These pictures were taken in 2010. None of them are edited or altered. They show details from breakwaters at Church Cliff in Lyme Regis, Dorset, that jutted out at right angles to the old sea wall. In combination, the structures were designed as coastal defences to protect the base of the soft crumbling cliffs from erosion by the sea. It was clear that the breakwaters, or groynes, had seen better days and were in need of repair. The iron that was supporting and holding the timbers together was very rusty. A lot of the woodwork was missing. In fact, they were very dilapidated but full of interesting colours and textures. The images in this post focus mainly on the corroding ironwork and include context shots to set the scene. Much has changed since these photographs were taken.
All around our British coasts we can see evidence of coastal erosion. It seems to be happening at an ever increasing rate in recent years. It is especially noticeable where the edge of the seashore is composed of softer rocks or sand dunes, for example. The coastline of Dorset in England, like many other places, is vulnerable to coastal erosion. Studland Beach near Poole Harbour is a case in point.
The shore of Studland Bay is divided into three stretches: South Beach, Middle Beach, and Knoll Beach. At South Beach, we have already seen how the burrows of small marine worms help to break up the surface of the chalk that underlies the beach in an almost imperceptible process called bio-erosion. However, the physical, hydraulic, and abrasive action of high energy destructive storm waves on the soft materials of the cliff is the coastal process responsible for immediately obvious damage with a wearing-away and break-up of the rocks and other materials on the upper margin of the seashore.
This destructive action of waves is most apparent from the number of small land slips, and trees that have collapsed to the beach, as cliff material [like London and Creekmoor Clays, and Broadstone and Oakdale Sandstones] has washed away from beach level. This has caused the undermining of the cliff deposits, and the eventual fall of material from higher up. There are a number of trees lying in a horizontal position at the base of the low soft cliffs on South Beach.
Where the ground level changes from cliff top to nearer beach level, the wearing away of the soil by the waves means that the trees now seem to be growing directly from the seashore with nothing but sand and pebbles around their roots and trunks. Just a short distance north of these beach-bound trees there are numerous beach huts on the slightly higher ground behind the shore. They are in a vulnerable position. Here the soft ground on which the huts stand is protected from the destructive force of wave action and flooding by the emplacement of stone-filled wire cages known as gabions. These are stacked to form a barrier wall of harder material that is more resistant to erosional coastal processes.
There were no other visitors on the dull day that we turned off the Cabot Trail to look at the Corney Brook shore in the western Cape Breton Highlands. There was very low cloud cover, and it began to rain after a while, but there were treasures to be found – at least if you are like me and are fascinated by beach stones. Three main rock types are found at Corney Brook. The oldest are Neoproterozoic-Ordovician granitic pluton rocks of the Bras D’Or Terrane. Ordovician-Silurian metasedimentary rocks of the Aspy Terrane are slightly younger. And red sandstones and conglomerates belonging to the Horton Group come from the Devonian to Carboniferous Period.
The stones on the beach include all three types and probably a lot more due to the glaciation of the area. I wish I could identify and tell you the exact composition of each photographed pebble, stone or boulder – but that is tough for an amateur to determine. There is a great variety of colour, pattern, and texture to the stones which look dull when dry but amazing when wet. They include igneous and metamorphosed rocks like granite, gneiss, schist as well as sedimentary rocks like sandstone. It is possible to see just how difficult it is to not only understand the texts but also to convert into straight forward language for the non-specialist reader from the following detailed description that I discovered about the Corney Brook schist by Jamieson et al. (1987).
Comey Brook schist (unit 3d)
Medium- to high-grade pelitic and semi-pelitic schists, with minor marble and psammite, occurring on the Cheticamp River, Corney Brook, the northeastern end of Jumping Brook, and the central highlands near Calumruadh and Coinneach brooks, are referred to here as the Corney Brook schist. This unit is equivalent to the “medium grade belt” of Craw (1984). Pelitic and semi-pelitic members of the unit characteristically contain coarse staurolite, biotite, and garnet porphyroblasts, with kyanite at the highest grade, in a phyllitic to schistose matrix. Medium- to high-grade marbles, quartzites, albite schists and hornblendite recognized in the Corney Brook area (Plint et al., 1986) have not yet been identified south of the Cheticamp River. Centimetre- to metre-scale compositional layering, folded by tight to isoclinal folds, is interpreted as transposed bedding. Based on bulk compositions and rare relict primary textures, the Corney Brook schist is interpreted to have formed as a suite of clastic sediments interlayerd with felsic tuffs and minor basic flows – that is, it appears to represent the higher grade equivalents of units 3a-3c.
The softer sandstone cliffs are being eroded back by the sea. This has implications for the ground higher up and the roadway further back from the shore. For this reason a sea defence structure has been emplaced to protect the base of the cliffs. This is a gabion made of wire cages full of large beach stones and boulders that are stacked up into a wall, positioned at the most vulnerable part of the shore.