The Shore Below the New Sea Wall (Part 2)

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 Below the New Sea Wall (Part 1)

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.

Low Tide at Lyme Regis

View from Lyme Regis over low-tide beds of seaweed towards the Cobb

The tide went out a long way on 10th March 2012. A very long way. For the first time ever I was able to see the glory of the hitherto hidden acres of golden-fronded kelps, brown fucoids, and red seaweeds carpeting the rocks at Lyme Regis. Usually when I visit the water is high on the shingle beach but on this occasion I could follow the water as it went out over the sand and rocks to get an entirely new perspective by looking up the shore, to the Cobb, the town, the fossiliferous cliffs of Black Ven and Charmouth to the east, including sight of Golden Cap. I didn’t know it at the time but this was the last time I was going to see the old breakwaters at Church Cliff.

Beds of seaweed exposed at low tide in Lyme Regis

Low-tide expanse of sandy shore at Lyme Regis in Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweeds at Lyme Regis in Dorset, UK, along the Jurassic coast.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed beds at low tide in Lyme Regis, Dorset, UK.

Seaweed-filled rock pools at Lyme Regis in Dorset, UK.

Seatown Strandline

The beach at Seatown in Dorset comprises a series of steep pebble banks. You can see how far up the shore the last high tide has been by the line of natural debris extending along the shore parallel to the water’s edge. On this occasion the strandline was almost entirely made up of dried red seaweed which contrasted well with the pebbles. Quite a number of white cuttlefish bones rested on the weed. I am fascinated by their beautiful structure. For some reason, the shape of the more concave surface (as in image 5) always makes me think of angels.

Wealden Beds at Lulworth Cove

There are five main types of rock strata visible at Lulworth Cove: Portland Stone, Purbeck Beds, Wealden Beds, Greensand and Chalk. The Wealden Beds are the most colourful and some of the rocks have wonderful patterns as well.

The colours range from yellow and orange through to deep red, brown and black. The strata are very variable with interesting textures and compositions.

Although this World Heritage Site is called the Jurassic Coast, it includes earlier Cretaceous rocks as well. The Greensand, Chalk and Wealden Beds all belong to the Cretaceous period. The photograph above shows the soft sandstone layers at the base of the cliff that are being worn back and undercut by the sea.

The photograph below shows a general view of part of the cliff containing the Wealden Beds.

For more information about the geology of Lulworth Cove look at the Lulworth Web Site.

Revision of a post first published 3 June 2010
COPYRIGHT JESSICA WINDER 2012
All Rights Reserved

A basket of Jurassic pebbles with white lines

A basket of pebbles with patterns of white lines, from the Jurassic Coast, Dorset, UK (1)

People like pebbles. I don’t know why. For different people at different times the reason may change. They can be beautiful, interesting, evocative, souvenirs. They come in a handy size for picking up and pocketing. They can be reminders of happy times in the relatively recent past as well as representatives of the geological past. They can also symbolise survival, endurance, resistance, resiliance. They are the end products of years of shaping by massive external events and processes. They encapsulate and demonstrate their history in the way they look today. Pebbles are beguiling.

Click here for more pictures of PEBBLES in Jessica’s Nature Blog.

A pebble with white lines from the Jurassic Coast, Dorset, UK (2)

A pebble with a pattern of white lines from the Jurassic Coast, Dorset, UK (3)

A pebble with a pattern of white lines from the Jurassic Coast, Dorset, UK (4)

A pebble with a pattern of white lines from the Jurassic Coast, Dorset, UK (5)

A basket of pebbles with white lines from the Jurassic Coast, UK (6) 

Revision of a post first published 15 February 2010

COPYRIGHT JESSICA WINDER 2011

All Rights Reserved

Winspit Waves 2

The waves breaking on the man-made rock ledge at Winspit, Dorset, UK on the Jurassic Coast.

The waves breaking on the man-made rock ledge at Winspit, Dorset, UK on the Jurassic Coast, where stone was quarried long ago and loaded straight onto boats.

CLICK ON THE IMAGE BELOW FOR A SHORT VIDEO OF THE WAVES

COPYRIGHT JESSICA WINDER 2011

All Rights Reserved