Pecca Falls [SD 695 749 – 695 752]
The video shows the Pecca Falls. As you crossed the bridge before walking up the path that runs along side these waterfalls you will have noticed a large quarry to the west. The rocks exposed in Pecca Quarry are Lower Ordovician slates. They dip at a very steep angle, almost vertical in some places, but generally around 65 degrees.
Pecca Falls are consequence of this steep angle of dip. In this part of the channel the River Twiss flows over steeply dipping alternating beds of slates (as seen in Pecca Quarry) and sandstone. Laid down in the Lower Ordovician, the slates and sandstones were tightly folded during the Silurian into almost vertical ‘concertina’ layers.
The sandstones are tougher and more resistant than slates, so as the river eroded the bedrock a series of steps developed. The harder sandstones form protruding beds over which the water falls into pools developed in the in the softer slates.
Use the menu on the right to view photographs of Pecca Falls and a diagram of how the waterfall was created.
Use the controls at the bottom of the movie to control playback