Two short walks and a quarry visit with the local geological study group helped to connect the geology of Dartmoor, tor formation and the surrounding scenery.
The first to Cox Tor (SX530761) started unpromisingly as a constant drizzle and a chilly morning meant that all the waterproofs were on before we left the car park (SX531751). The kids in this instance were much better off than the adults as they had new jackets and shoes, whereas ours were somewhat less than showerproof.
The way up was a fairly steady pace on a wide and clear path into the mist, pausing as we reached the top of each steep section. At the last rise before the summit we took a slight detour to the clearest rock outcrop to view the frost induced fractures in the rock face and to consider the clitter field of broken rocks at the base.
The kids enjoyed scrambling over the somewhat slippy rocks, then it was on to the top. A brief stop at the exposed trig point was just enough to survey the topmost terraces which were created by the frost induced fracturing and subsequent solifluction processes. The base material – diorite and metadiorite allows these erosion processes to form distinctive “cryoplanation” benches which advance into the higher ground. The issue is not necessarily settled, however, as questions have been raised about the timescales associated (eg –eg Migon).
On the descent, Kieran and his new friend Amy spotted an old quarry (SX531757) which gave an opportunity to observe the strike and dip of the bedrock material. We’d separated from the main group for this detour, but in his eagerness to catch up Kieran managed to trip & fly headfirst down the slope. His feet and body stayed dry, but some waterproof trousers would have been useful!
After getting back to the car, we promptly made off for the next stop as it was getting on for lunchtime. The parking lot at Two Bridges (SX609750) is in a disused quarry and affords a view of both block granite and weathered granitic material crossed by a dyke. The joint controlled erosion of the block granite was discussed, along with the role played by chemical weathering. The difference between the fine grained meta-diorite of Cox Tor and the coarser lighter granite and meta-granite structure was obvious as were the large proportion of feldspar crystals.
Lunch was taken at the Badgers Holt (SX672735). I can heartily recommend the homemade Steak & Ale Pie, though Kieran’s chilli-con-carne wasn’t to his taste!
Our last stop was Hay Tor (SX758770), a popular destination by this time as the clouds had lifted. My time was spent ensuring Hazel & Kieran didn’t climb anything too ambitious, though the ascent isn’t required to take in the distant views of Torbay. The Tor itself is impressive standing a good 10m above the grassy base, and the granite itself is marked by the large feldspar phenocrysts.