[2][3] The islands are largely managed as nature reserves by the Isles of Scilly Wildlife Trust, principally for breeding seabirds and grey seals (Halichoerus grypus).

[4] All of the Western Rocks are composed of Hercynian granite of late Carboniferous age with thin podzolic soils on the larger ones.

The larger islands in this archipelago are, from north to south: Great Crebwethan, Rosevear, Rosevean, Daisy and Pednathise Head (the most southerly point of the United Kingdom).

Area is measured at MHWS (figures are provided by the Isles of Scilly Wildlife Trust): (grid reference SV839053) 0.57 hectares (1.4 acres) in size.

Gilstone has been the cause of many of the shipwrecks recorded in the Isles of Scilly, most notably the sinking of Admiral Sir Cloudesley Shovell's flagship HMS Association in the naval disaster of 1707 with the loss of over 1400 lives.

The only plants recorded are common scurvygrass (Cochlearia officinalis), rock sea–spurry (Spergularia rupicola) and orache (Atriplex sp).

Plants recorded are tree mallow (Lavatera arborea), spear-leaved orache (Atriplex prostrata) and common scurvygrass.

(Cornish: Ros Vian, little promontory) (grid reference SV839056) 0.63 hectares (1.6 acres) in area and the highest of the Western Rocks with a maximum height of 17 metres (56 ft).

Apart from the occasional plant Rosevean consists mainly of bare rocks and is important for its breeding birds and, as a haul–out site for grey seals.

[2][3] Unlike the rest of the islands, there is no evidence of any human occupation on the Western Rocks, apart from the Herbert salvage expedition in 1709 and 1710, and as a temporary worksite on Rosevear in the mid–nineteenth century.

With a poor understanding of the sea current in the western approaches, which pushed sailing ships further north than expected, and the problem of pre-1750 charts showing the rocks ten miles further north than they actually are, it is not surprising that throughout history the Western Rocks have witnessed a great number of the shipwrecks recorded in the Isles of Scilly.

In 1841 the captain of a paddle steamer SS Thames mistook the lighthouse on St Agnes for the Longships and changed course to head north.