"Mark Godden's Little Bit Of Cyberspace Mk.II"

The Southwell Landslip

 

Ancient landslips, such as this one between Church Ope Cove and Southwell were the sites of Portland's first large scale quarries. The gorge at the right hand side of the above image, is a gully (or master joint) that has widened, as the seaward side rocks have dropped and slumped outwards. This movement has occurred because the soft Kimmeridge clay that underlies the stone, has been eroded (from the outside) by the sea, partially undermining the stone. Groundwater at the junction between the clay and the stone, no doubt contributed to the collapse. Early quarrying activity once took place in the area to the foreground of the picture.

This classic failure mechanism, almost certainly operated to the north of the Southwell Landslip, in the area that is now the East Weirs, where it is probable that much of the stone for St Paul's Cathedral was quarried. Mass movement of the type pictured made access to the stone beds easier and the proximity of the sea was beneficial, as the stone, once quarried was transported to London, on sea-going barges. Interestingly, it was instability, resulting from movement of this type, that led to the eventual abandonment of St Andrew's Church at Church Ope, in the mid-Eighteenth Century.