John Archer Thomson was the speaker last Friday at Tenby Arts Club. His topic was the geology of Pembrokeshire, a subject he has been taking an interest in since he visited Pembrokeshire as a student. The photographs in his presentation ranged over the last 40 years, and often showed the changes that have occurred in this time.

Starting up in the older northern end of the Pembrokeshire coast at Cenmaes Head, John slowly took us south, seeing seals, finding out about sixth century saints, hearing about baby floating competitions, and seeing patches of maritime heathland now rare in this country. From Ordovician rocks, submarine volcanoes and pillow lava to finding out that a lot of the Pembrokeshire coastal area was an ancient sea floor. Pembrokeshire’s own Giant’s Causeway (well, the same rock structure, anyway!), the difference that the Normans made to farming methods in the north and south of the county, and the harbours used for importing guano from Chile and timber from Newfoundland all appeared in this fascinating talk. Did you know that slate occurs when magma meets rock? That the wild ponies help to keep the coastal edges open land for the choughs to live on? That you can see scratch marks on the cliffs from the glaciers sliding past?

Reaching St David’s, the longest continuously used religious site in the UK, where the floor of the cathedral slopes up and the pillars lean in to enhance the feeling of being humble before the Lord, and St Justinian’s (he led such an austere order that the monks ended up chasing him around Ramsey Island with an axe), the talk ended in the more sedimentary rocks of St Bride’s Bay and Newgale.

Having only made it half way round the county, John promised to come back again and complete the tour. Something to look out for, indeed!

This Friday, February 4 at 6 pm in St Johns Church Hall, Warren Street, local artist, Guy Manning will be giving a talk and demonstration. Everyone is welcome, entrance is £5 or £3 if you are a member of the club, which includes the tea or coffee and biscuits at the end.