We often visit the beautiful settings of Dartmoor but how many of us understand the origins of the rock formations which make up the Dartmoor landscape? Dr. Richard Mayhew provided members with an entertaining and educational talk entitled The Geology of Dartmoor.
Richard started his talk with pictures of other well-known beauty spots – Snowdonia, the Lake District and Gordale Scar near Malham with its limestone ravine and surrounding pavings and compared these with the more gentle landscape of Dartmoor.
Members were each handed a sample of Dartmoor granite rock with different faces, being polished, cut or rough. Here one could clearly see the composition of the granite samples – white feldspar, grey quartz and black mica in a tightly packed matrix.
There are two theories on the formation of the Dartmoor tors. Professor David Linton proposed that the tors were formed by a rotting process or deep chemical weathering. Palmer and Neilsen suggested that surface weathering occurred during periglacial periods bringing rise to the clitter (strewn rocks) surrounding the tors. Members were shown example photographs of various tors each with their own unique structure and showing how mining activities account for some of the distinct shapes.
Tony Dunk thanked Richard for his most interesting and informative talk. Members then proceeded to Tavistock Golf Club where an excellent Christmas lunch was served. The subject of the January meeting of the Tavistock Probus Club is “The Defence of Rorke’s Drift”.
Anyone interested in the Tavistock Probus Club may contact the secretary on 01822 615669.