Cliffs and seashore

At low tide it is worth walking out on to the rocky shore platform which gently slopes away from the base of the cliff of Haven Brow. As the cliffs are cut back by waves, the platform is planed off to relatively level surface, although in detail it is irregular, with rock pools, steps and runnels into which the ebb and flow of the tide is channelled.

Flint, which is common in the cliff at Haven Brow, consists of a mass of minute crystals of silica. It is black with an outer whitish crust or cortex and occurs in the chalk as nodules (scattered or in bands); or in tabular sheets. Although usually running parallel to the bedding of the chalk, it sometimes fills vertical or oblique cracks. Occasionally you may find sea urchins in which the original calcite shell and soft parts have been replaced by silica and you then have a flint fossil. The formation of flint has been the subject of considerable debate and although there is no single acceptable theory that explains the origin of all its forms, it seems probable that both physical and chemical processes were involved. On the other hand there is little controversy over its use. An early source of fire made by knocking together two pieces of flint, or flint against pyrites to produce a spark, its splintery nature was also exploited by Stone Age man in the manufacture of his artifacts (tools and weapons) and for crude operations on the brain. For hundreds of years its hardness has been used to advantage in the building industry, as for example, in the walls of the Park Centre (roughly trimmed), and Exceat Farmhouse (seashore cobbles in southern facade), and more recently as crushed aggregate for concrete.

Being a very soft rock, the chalk which has fallen from the cliff erodes away from the hard flint which then often accumulates as a shingle beach. Wave action batters the individual flints together and they become rounded (but rarely spherical) pebbles; in the process they may become stained by minerals in the sea water. Because waves generally approach this coast from a southwesterly direction, the shingle tends to drift along the beach from west to east. Until the timber-training walls at the mouth of the Cuckmere were built, the river mouth was frequently diverted eastwards towards Haven Brow and evidence of this movement in the past can sometimes be seen today at very low water in the form of a sand bar.

On the beach you may sometimes find heavy rust-looking spherical or sausage-shaped lumps which are not thunderbolts or meteorites, but the iron sulphide mineral pyrite or marcasite. If broken (take care) they reveal a mass of radiating golden crystals which rapidly oxidise and tarnish - fools' gold!

Birds crowd the relatively few stable cliff ledges suitable for nesting and you may well see fulmars, herring gulls and jackdaws flying around them.

Shingle Flora

Shingle plants usually only grow on the sheltered parts of beaches because exposed shingle is very mobile in onshore gales and the plants would become dislodged. Perhaps surprisingly, there is no lack of water in shingle beaches and the plants are not specially adapted to growing in high salt concentrations. Where the shingle has been stable for some time, the vegetation is much denser and additional species such as grasses and mosses become established.