A gorgeous example of a cliff rockfall at Broad Haven, Pembs -- not far from the Sleek Stone. The cliff face here is at extreme HWST -- which means that storm waves do hit this rock face occasionally. The Coal Measures sandstones and shales are here intensely fractured, and the "solid" rock is riddled with fracture planes running in many different directions. Groundwater has been percolating along these fractures and precipitating iron oxides, which explains the heavy "rust" staining. This process of precipitation and water seepage might well have facilitated the breakdown of the cliff.
Within a few years, this iron oxide will have washed off the newly exposed rock face, the the scar left by the rockfall will not be so prominent.
I hope to goodness that no archaeologists visit this site, or before we know where we are, we will have another quarry on our hands.........
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