Multidisciplinary studies carried out in advance of site investigations of the areas at Lyme Regis, Dorset most threatened by a
combination of landslides and marine erosion included sidescan-sonar, bathymetric and seismic-reflection surveys in the adjacent
offshore area. These revealed a large area (over 1500 m long x 700 m wide) 500 to 700 m offshore from the present-day coastline
in which an irregular sea bed is strewn with rock debris. This area is underlain by a layer of heterogeneous material up to 30 m
thick with traces of disturbed bedding and shear planes. Comparison of the stratigraphy and structure of the underlying in situ
beds, as determined from seismic-reflection surveys, suggests that the disturbed material is the residue from a single large
(> 10 million tonnes) landslide that resulted from a shear failure in seaward-dipping mudstones in the lower part of the Jurassic
Charmouth Mudstone Formation. A reconstruction of the geology immediately prior to the landslide indicates that the failure
occurred at a time when the cliff line was c. 350 m south of its present position, possibly in the mid Holocene 5000 to 6000 year
ago when sea level was sufficiently high to re-erode a Pleistocene cliff line
Is data on this page outdated, violates copyrights or anything else? Report the problem now and we will take corresponding actions after reviewing your request.