I was strolling along, admiring the view, beside the crowded St Peter Port Harbour in Guernsey when suddenly I realised that a big bird with very large webbed feet was walking past me on the pavement. Surprised, I spun round with camera in hand, for a better look and the bird did the same, craning his neck to stare right at me before nonchalantly waddling on.
This gallery contains 15 photos.
A sand bar spreads southeast from Whiteford Point in Gower, South Wales. At low tide in the Burry Estuary, it is part of a very extensive sandy area over which cockle and mussel fisherman can traverse in vehicles from places further along the north Gower coast. The sand depth is variable and mostly envelops a spit of pebbles. Sometimes the pebbles are entirely hidden. Sometimes they are partially exposed. Intermixed with the pebbles are seashells – cockles, mussels, whelks, and oysters are the most commonly occurring. There is a wide range of colours and textures in the pebbles and they are particularly interesting because of the range of rock types they represent.
As you take a 360 degree scan of the horizon from this isolated expanse of sand and pebbles, there is not a single rocky outcrop in sight. So where have these beach stones come from? The collection includes sedimentary rocks from the locally occurring Carboniferous limestone and Devonian sandstones, mudstones, and conglomerates – like the bedrock exposed at Rhossili and at Broughton Bay. It also includes samples from higher up in the Carboniferous strata such as the Millstone Grits, sandstones, and shales, and Coal Measure layers. These strata underlie the Burry Estuary into which this spit extends, east Gower, and the Swansea district and way beyond. There are many rock types with which I am not familiar but I notice that some are metamorphic and igneous in nature. So how have all these rocks ended up on this spit, far from their place of origin?
Part of the answer is undoubtedly the effect of sea drift, currents, and storms carrying weathered and broken stones along the shores of Carmarthen Bay and into the estuary or inlet – but a significant proportion of the stones are thought to have been brought to the area from considerable distances away by glaciation, and deposited by the melting of an ice sheet, possibly in the late Devensian era about 24,000 years ago. Most of these stones lie hidden in a mass beneath the Whiteford Dunes but some are exposed high on the shore at the foot of the dunes, and beneath the disused iron lighthouse on Whiteford Point. Over time the waves have dislodged the often frost-shattered stones from the surface of the deposit, and washed them further along the beach around the Point to form pebble spits and banks, in the process smoothing and rounding them into the pebbles visible today.
I found this tiny hermit crab scrabbling around in the seaweed and seashell debris of a sandy tide pool beneath Rhossili cliffs. I thought at first that it was just a very small, immature, specimen of the common hermit crab (Pagurus bernhardus Linnaeus) but as soon as I picked it up for a closer look I could see that it was something special because it had a large claw (cheliped) on the left instead of the right. There is only one species with this characteristic – the south-claw hermit crab, Diogenes pugilator (Roux). The mature specimens have a greenish carapace no greater than 11 mm in length.
According to Hayward and Ryland (1998) this crab lives in fairly sheltered sandy bottoms from low water spring tide level down to 35 m, on south and west coasts of the British Isles where it is described as common. It also occurs elsewhere from Holland to Angola, Mediterranean, Black Sea, and Red Sea. Mullard (2006) provides more information, saying that D. pugilator is only found in a limited number of places in Britain and Ireland because it is primarily a warm-water species and may be worthy of further study in relation to climate change since there are signs of it extending its range. It was first recorded in Britain “at Worms Head” from specimens provided by L. W. Dillwyn of Sketty Hall in Gower to Spence Bate in 1850 who described it in Annals and Magazine of Natural History.
The crab can quickly bury itself in clean, well-sorted sand on a gently shelving moderately exposed beach facing southwest where conditions are less turbulent than on steeper beaches. This crab has an interesting extra way of gathering food, in addition to scavenging or eating sediment. While mostly buried in the sand, it can sweep its hairy antennae around in an almost circular motion as a net to capture small edible particles from the water.
Hayward, P. J. and Ryland, J. S. (eds) 1995 (revised edition 1998) Handbook of the Marine Fauna of North-West Europe, Oxford University Press, New York, pp 434-437, ISBN 0-19-854055-8.
Mullard, J. 2006 Gower, The New Naturalist Library, Collins, London, pp167-168, ISBN0-00-716066-6.
These rocks are seen on the west side of The Island or St Ives Head in Cornwall, England. They form outcrops on the west side of Porthmeor Beach. I was fascinated by the sheer complexity of the colours, patterns and textures. As far as I can make out they belong to an un-named igneous intrusion (matagabbro or metamicrogabbro) composed of silica-poor magma which was later altered by low-grade metamorphism in the Devonian period between 359 and 416 million years ago.
The rock looks very different from that nearby which was featured in an earlier post. I was particularly drawn some outcrops which had an almost dark navy blue smooth surface but the majority of the rock surfaces were blue-grey and dirty yellow shades – some with smoother almost layered textures and others textured like lumpy porridge. The patterns were complex but included ancient splits and cracks that had been infilled with other materials of contrasting colours, giving paler or darker straight lines and angled cross lines – not to mention all the complicated later fracture patterns. There seemed to be large inclusions of other rock types too; this often occurs in granites. It is incredible that rocks of the same basic type can vary so much in their appearance within a few metres.