ABSTRACT
The coastline of the Isle of Portland in southern England is marked by various types of slope failure, particularly deep-seated compound landslides developed in Kimmeridge Clay overlain by the Portland Sand and, above, the Portland Stone. For a length of several hundred metres on the eastern side, the coastal limestone cliffs include a substantial toppling failure. Topples are rare in the British Isles and this is possibly the largest that exists at present. It occurred in 1734 and is known as the Great Southwell Landslip. The timing of the failure demands detailed examination, coinciding as it does with the cooler and wetter climate of the ‘Little Ice Age’ but also with the onset of industrial activity by the population of the time. This paper explores the role of these factors in the occurrence of the failure, including whether they accelerated the timing of failure and/or influenced the mode of failure given the stratigraphic context of the site.
