Fractured 11-14

Natural fracture patterns in Jurassic rocks at Seatown in Dorset, England, re-coloured with digital wizardry.

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.

Rocks at Cape Tribulation

The striped and layered rocks that underlie the promontory at Cape Tribulation look like sedimentary strata. They were just that at one time in the past but they have been  altered and partly metamorphosed into metasedimentary rocks. They belong to a group known as the Hodkingson Formation and are the result of transformations brought about as two tectonic plates of the earth’s crust collided, with one plate then sliding under the other (subduction), generating tremendous heat and pressure that altered existing sedimentary rocks, promoted magma movements below the crust (leading to intrusive igneous rocks), and stimulated surface volcanic activity (making extrusive igneous rocks).

Fractured 7-10

Yet more natural fracture patterns in Jurassic rocks at Seatown in Dorset, England, re-coloured with digital wizardry.

Worked Stone – Veltha by Emily Young

I am overwhelmed by the beauty of the Emily Young sculptures that are periodically exhibited in London locations for all to appreciate. Not only is the working of the stone exquisite but the selection of the stone for the work itself is amazing. As an amateur geologist I am fascinated by the range of colours, patterns, and textures naturally occurring in rocks, and to see them used to such great advantage is a privilege. I discovered an exhibition of Emily Young’s sculpted heads in the Southwood Garden attached to St James’ Church near Piccadilly on my last visit to London. They will be on display until January 2018. These pictures show aspects of a sculpted head called Veltha which is created in brecciated onyx, and it is displayed by courtesy of Bowman Sculpture.

The Beach Below The Spittles 2

Pieces of shale on the beach with holes made by piddocks

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.