We went down Cwm Nash last weekend.
This photo is at the end of the Cwm (valley) looking back inland. It’s quite interesting because all of the rock either side here (out of view) is grey liassic limestone that weathers to a light buff colour. But all of the buff coloured cliff face here is post glacial tufa. Tufa is a calcareous deposit. All of the cliff that you can see here is lime that has precipitated from the valley stream since the last ice age – only about 12,000 years ago. So the cliff has slowly built up from the stream. The stream is currently quite small and now comes out of the bridge structure over to the right.(more…)