Landslides in blanket peat on Cuilcagh Mountain, northwest Ireland

• Published in: Geomorphology (Amsterdam, Netherlands) Netherlands), 2008-12, Vol.102 (3), p.325-340
• Main Authors: Dykes, Alan P., Gunn, John, Convery (Née Kirk), Katie J.
• Format: Article
• Language: English
• Subjects: Blanket bog; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geomorphology, landform evolution; Marine and continental quaternary; Mass movements; Natural hazards: prediction, damages, etc; Northwest Ireland; Peat slides; Stability thresholds; Surficial geology
• ISSN: 0169-555X; 1872-695X
• DOI: 10.1016/j.geomorph.2008.04.003

The northern and eastern sides of the Cuilcagh Mountain upland, in northwest Ireland, are mantled with over 50 km 2 of blanket bog that has experienced an unusually high spatial and temporal frequency of peat mass movements. In all, 29 peaty-debris slides, nine bog slides, two peat slides and five more peat landslides of uncertain type have been recorded within this study area. More than 27 km 2 of this peatland has been afforded several levels of statutory protection as well as international recognition of its geo-environmental importance. Field and laboratory investigations of the peat at several of the more recent failure sites showed it to be typical of Irish and Pennine (northern England) blanket bogs in most physical and hydrological respects. Field geomorphological evidence and modelling of stability thresholds indicate that the particular susceptibility of the Cuilcagh Mountain blanket bog to failure arises from two local factors: (i) the attainment of threshold maximum peat depths on the East Cuilcagh plateau, and (ii) the unconformable deposition of thin layers of glacial till (in places) and blanket peat over the pre-existing topographic surface formed from the major shale formations that underlie the northern slopes. With two exceptions, there is no conclusive evidence that human activities and management strategies for the area have had any significant influence on the occurrence of the peat landslides. The high frequency of large rainfall events since 1961 that did not trigger landslides suggests that failures are unlikely to become more frequent in response to climate change effects because they are controlled by slowly changing internal thresholds.