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Evidence of glacial activity can be found throughout Scotland, and Loch Lomond offers one of the most accessible regions where this can be seen. The area formed a main channel for the advance of ice southwards during the last ice age, with the loch itself forming as the result of the removal of large quantities of rock, dug-out by movement of the ice. Glacial features found here include corries, hanging valleys, drumlins and other glacial sediments such as till and boulder clay. However, the southern end of the loch is the type area for the Loch Lomond Stadial, a cold spell approximately 11,000 to 10,000 years ago that caused the readvancement of glaciers across western Scotland. Study of the landforms and sediments deposited in the area have allowed for the understanding of the evolution of palaeoclimatic changes during the Late Devensian and Holocene.
Following the end of the last Late Devensian ice age (approximately 12,000 years ago), rising sea levels meant that the southern end of the loch was invaded by the sea. A distinctive shore platform along the southern shore and the deposition of the marine Clyde Beds are the result of this invasion. The Clyde Bed sequence found at Geilston has allowed for the study of marine palaeoenvironmental conditions during the late stages of the Late Devensian.
However, rising sea levels following the Loch Lomond Stadial (11,000 to 10,000 years ago) resulted in a further two phases of marine transgression. This resulted in the formation of raised shorelines and further deposition of marine sediments. Glacial deposits from the intervening Loch Lomond Readvance are found as the Gartocharn Till.
The view north up Loch Lomond from its southern end – the Highland Boundary Fault runs across the Loch and can be traced across the islands of Inchcailloch, Torrinch, Creinch and Inchmurrin. © Scottish Natural Heritage.
Browne, M. & Mendum, J. Loch Lomond to Stirling – A Landscape Fashioned by Geology. Produced by: Scottish Natural Heritage & British Geological Survey.
Gordon, J.E. & Sutherland, D.G. 1993. Quaternary of Scotland, Geological Conservation Review Series No. 6., Joint Nature Conservation Committee, Peterborough.