Fairlight Cove Geology

Cliff Section 3:

West of the Fairlight Cove Fault

The Fairlight Clay exposed in the cliff consists of grey/green silty clays with occasional thin sandstone and siltstone beds which are extremely variable. The strata are again folded into a gentle anticline with a WNW/ESE trend. Whilst rain water infiltration into the clays is limited, it is thought it plays an important part in pore pressure conditions which affects cliff stability.

Failure of the cliffs in this section is by processes of mass flow and failure of large sections of the cliff, leaving behind a scarp in the cliff with a number of terraces on the slumped mass. Over time these terraces are degraded by further mud flow processes. The slump continues to slip as the toe of the mass is eroded and by landward failure of the rear scarp. This style of cliff failure is seen in the recent slide which initially occurred in 2000 at Rockmead Road and resulted in a large part of the cliff slipping onto the beach, with the loss of several homes.

The shingle beach provides some degree of protection to the cliffs in the area. At Rockmead Road, the cliff comprises the toe of the landslide which in places is up to 10m high. The material is loose and unconsolidated and easily eroded by wave action. Erosion and removal of material of the toe seems to be promoting further displacement of the landslide with evidence of heave on the beach. Continued seaward displacement may occur due to regressive failure of the rear scarp of the slide, adding more mass to the slide with the effect of gravity causing rotational movement of the mass.

The effect of groundwater and surface water on the failure process is uncertain. For while the sea erosion of the toe of the landslip is occurring, continued seepage of water onto the benches and scarps of the landslip appears to cause further recession of the landslip.

Clay cliffs typical of this section

Mud runs on the cliff face

View of the most recent large scale landslide (Rockmead Road Landslide) taken in March 2004