Beach and Dune - Gower - page 140

SHINGLE
The origin of the term 'shingle' is not clear, but it has been used for centuries to describe beaches com-
posed predominantly of rounded pebbles. Shingle is defined as sediments coarser than sand, and smaller
than a boulder, that is between 2 and 200 millimetres in diameter. Shingle beaches tend to form in high-
energyenvironmentswheretheseacanmoveandpileuppebblesontheshoreabovethetideline.Coastal
systems dominated byshingle are an internationally important but diminishing resource as, like the sandy
beaches, most are essentially relict features formed during the last glaciation. There are about sixty major
shingle structures in Britain and two of these occur in Gower, at Pwlldu and Pennard. In addition there
is a large relict shingle beach buried under the dunes at Oxwich (see Chapter ) , and smaller structures in
Port-Eynon Bay at Horton, in Rhossili Bay and Oxwich Bay, and at Whiteford Point and Loughor. In the
1ate 1920s there was also a shingle beach at Salthouse Point, Crofty, the shingle resting on firm sand that
extended for a considerable depth below it, but this has now disappeared.
Together the remaining features provide a unique habitat for wildlife in the peninsula. Many shingle
beaches in Britain are now heavily managed for coastal defence and increasingly for 'conservation'. In
contrasttheshinglebeachesofGower,althoughcomparativelysmallinextent,representsomeofthemost
unaltered examples of this habitat in Britain. Experience has shown that wherever possible shingle struc-
tures should be left completely alone, and the urge to preserve present features resisted, since in most
cases physical change in the structures favours ecological diversity.
Coastalshingleoccursinanumberofsettingsandformations.Ofthesixmaintypesrecognisedworld-
wide, three are represented in Gower. The three-ridge shingle beach at Pwlldu, which dams the Bishop-
ston Pill and fills the former bay, is an example of an 'embayment beach ridge plain' and consists of a
series of relict storm beach ridges and an active beach front (Fig. 74). The majority of such structures are
naturally dynamic and tend to move inland through a process known as 'rollover'. During major storms,
however, the crest of the ridge may be overtopped or breached, creating shingle 'aprons' that spread over
the rear area. Pure shingle is uncommon in western Britain and Pwlldu is therefore important in this re-
spect. But the shingle here is essentially anomalous in that the vast storm beach of limestone pebbles is a
relicoftheextensivelimestonequarryinginthenineteenthcentury.IncontrastthedoubleridgeatPennard
is seemingly natural and an example of a 'barrier spit', partially blocking the entrance to Pennard Valley
(and protecting a small salt marsh behind). The smaller shingle structures in Gower represent 'fringing
beaches', formed from an accumulation of shingle on the upper shore.