Читать книгу The Isles of Scilly - Rosemary Parslow - Страница 22

When the granite weathers it eventually becomes reduced to sand. Blown sand is an important constituent of the soils of all the islands as well as forming the beautiful white beaches and the sand bars that link many of the higher parts of the islands. Ram (also known as head or rab) is a cement-like material formed by the breakdown of periglacially frost-shattered granite fragments that forms deposits around the bases of granite carns, in valleys and especially in the cliffs (Fig. 8). It is often excavated from ‘ram pits’ to be used by the islanders as a mortar in building work and sometimes as a road surface. Alluvium is found under the Porthloo fields, and at Lower and Higher Moors. Small patches of gravel found near the daymark on St Martin’s and at a few other places are probably of glacial origin – see below.

FIG 8. Ram shelf at the base of the cliff on Samson. (Rosemary Parslow)

FIG 9. An example of a raised beach at Porth Killier, St Agnes, where former beach levels can be seen above the present beach. May 2003. (Rosemary Parslow)