Collectively the islands are represented by the Outer Hebrides island chain, the northern Inner Hebrides and Orkney and Shetland. The landscape is noted for its breathtaking contrasts from the rugged scenery of the mountains and rock-dominated landscapes of Harris, Rum, Skye and, to a lesser extent, Mull, to the undulating, dreary peat-dominated terrain of North Lewis and the gently undulating, subdued relief of Orkney and Shetland. Rock variety is considerable, the lithology and chemistry of the rocks affecting their response to weathering agencies and geomorphic processes. This contributes directly to the wide variety of landforms. Glaciation has been intense with Shetland, for example, experiencing total ice cover during all four maxima of the Pleistocene Period. However, on all islands, most of the glacial drifts have been deposited by the most recent glacial period which therefore plays the most important role by creating the parent materials. 
Colluvial material, including shallow drifts are widespread on the western islands with till deposits of medium to moderately fine texture more characteristic of Orkney. Recent deposits of windblown sand are well represented on the western fringe of the Outer Hebrides, from North Uist to Barra, the distinct machair soils being of locally high agricultural value.

Cultivated Machair on The Uists	Crofting township on Harris with cultivated lazy-beds in foreground	Improved agricultural land, Shetland
LAND USE On the western islands, free draining mineral soils associated with level or gently sloping terrain represent sites of locally high agricultural value. In other instances, such as Lewis, peat deposits on flat terrain have been stripped off to create agricultural land. Extensive tracts of moorland are used for rough grazing. Permanent pasture and cultivated land are widespread on Orkney with the latter restricted on Shetland to the mineral soils around the coast. Rough grazing is confined to sloping land where improvement is rarely economically viable but plays an important role because beef cattle and sheep rearing represent important farming practices. Rough grazing makes up 90% of the total land area in Shetland. Woodland is scarce on all the islands due to the frequency of gales, a high salt spray within the wind and the need to utilise the land primarily for agriculture.