Scottish landform examples 44: the Dirc Mhòr meltwater gorge

ABSTRACT

The Dirc Mhòr gorge in the central Grampian Highlands is 1.1 km long, ∼250 m wide and up to 110 m deep, and is incised in granite bedrock. It is the largest of several bedrock gorges that are incised into spurs, cols or plateau margins in the area, and its present catchment area is negligible. The floor of the gorge is covered by coarse rockfall debris, and the sides of the gorge are mantled by talus accumulations; surface water flow is absent. The gorge is inferred to have evolved over several glacial-interglacial cycles, with subglacial meltwater erosion deepening the gorge under successive ice sheets, and paraglacial rockwall collapse widening the gorge during intervening interglacial periods. Subglacial erosion may also have contributed to gorge enlargement as it widened.

KEYWORDS:

• ice sheets
• meltwater channels
• paraglacial
• rockwall collapse
• talus

Acknowledgements

I thank Graeme Sandeman for drafting the figures, Jon Merritt for useful discussion of the site and providing unpublished material and two anonymous reviewers for helpful suggestions.

Disclosure statement

No potential conflict of interest was reported by the author.

ORCID

Colin K. Ballantyne http://orcid.org/0000-0002-6044-9198