Aside from Hoy, the low, open valleys between ridges and which lie submerged the floor of the sounds are products of ice sheet erosion, with deformation of ice around high ground. On Hoy, the high ground is dissected by through valleys. In south Hoy, the valleys breach the preglacial watershed, with development of rock basins, now filled by lochs, where ice has been forced through narrow cols. The deep through valleys also reflect the penetration of tongues of ice within former ice sheets and the breaching of the watershed. Here, however, the valleys may have a compound origin, with initiation of deepening by corrie glaciers sourced on the high ground.

Glacially-overdeepened valleys in south Hoy, occupied by the Heldale and Hoglinns Waters -Image courtesy of Alan Moar

Glacial breaches in north Hoy -Image courtesy of Alan Moar

Glacial erosion

Glacial Landscapes

  • The Ice Age in Orkney

    During the periods of maximum cold in the Quaternary, major ice sheets covered Scotland. An ice stream hundreds of metres thick curved out from the Moray Firth to cross the plain of Caithness and flow over Orkney towards ice limits close to the edge of continental shelf.

  • Glacial erosion

    In the gently-dipping sandstone terrain of Orkney, it is often difficult to pick out classic landforms of glacial erosion. Low-lying areas often show a pronounced SW-NE grain to the topography, parallel to the main direction of ice sheet flow. ...

  • Glacial Deposition

    Glacial deposition is largely confined to low-lying areas on Orkney, where thicknesses of till may exceed 10 m. The glacial deposits drape the landscape, smoothing its outlines. Ice-marginal features are largely unrecognised outside Hoy ...

  • Glaciation of Westray

    Westray is the furthest northwest of the Orkney islands. The total area is 47 square kilometres, not huge but the irregular shape gives it a long coastline of almost 80 kilometres, a good place to look for glacial striations. The bedrock of the whole of the island is made up of the cyclical Rousay Flagstone Formation. ...