The main settlement on the island today is Biggings , which overlooks Housa Voe and is surrounded by in @-@ bye land to the east of the hill dyke ( which runs south from West Voe ) . To the west the island is bisected by a belt of glacial moraine about one and a half kilometres in length . Much of the rest of the area consists of a shallow stony soil that may be derived from glacial till . It is an almost complete absence of peat on the island and due to the volcanic rocks the soils are relatively fertile . The lack of peat led to ' turf scalping ' for fuel and the bare areas of rock in the interior .