Sunday, 10 July 2016

The South Hams

Unless you see it for yourself, it is hard to appreciate the level way the hill tops of the South Hams meet the Devon sky. Stopping my car between Malborough and Salcombe I see a flattish horizon lying around me: the hill tops mark the surface of a gently wavering plateau. Just a few gentle undulations here and there detract from the general impression of a broad concordance of summits in the countryside between Dartmoor and the coast.

You can only see this plateau landscape from high places; stand anywhere in between them and you will just see hills and valleys. Car drivers in the South Hams are forever climbing slopes or dipping into troughs - but summit views tell a wide and level story. In the same way, a trawler captain might rise to a wave top and see all crests forming a composite, flat horizon that belies the rising and falling of his little ship.

The high points include summits at East Prawle (443 m), Blackdown Rings at Loddiswell (580 m) and Stanborough Camp (700 m). Lying between them and the sea is a complex, rolling mass of lesser hills, slopes, valleys and coombes that form the physical heart of the South Hams. We should not forget the contribution made by the long, dendritic estuaries - the rias - that penetrate the land mass, where lower reaches of valleys such as the Erme and Dart have been drowned by the sea. These valleys continue inland and are fed by a welter of coombes scooped out of red-brown Devonian bedrock.

I have never understood the origins of this summit phenomenon. Old-time geographers talk about  peneplanation, suggesting that the landscape was planed off in the late Neogene period. My teenage mind's eye used to hold an image of an immense wave-cut platform uplifted and then dissected by rivers. That does not make sense. What about glaciation - have the summits been planed by ice sheets? There is no evidence that this landscape has suffered anything more than periglacial processes in the freezing hinterland beyond the southern limits of Pleistocene glaciation. The slopes and coombes are thickly bedded with frost-shattered debris, but not outwash gravels nor till - not even on Dartmoor. There remains the idea of subaerial erosion as the most plausible agent, set against a history of rising and falling land levels over millions of years.

The rocks underlying the South Hams are mostly of Lower Devonian age - mostly slates and mudstones, perhaps 410 million years old. You can see them everywhere in walls, or in rocky lanes.

Supposing the South Hams were an extremely ancient terrain, perhaps tens of millions of years old. Suppose an eroded landscape of Devonian rocks was once covered by the sea, buried in sediment and then uncovered - then perhaps buried again, then exhumed once more - and all the while the land levels and sea levels were rising and falling over immense stretches of time. The South Hams landscape may have been roofed and unroofed several times over, and what survives is a battered and extremely ancient relict terrain, now seen as a complex of flat summits, hills and coombes - over which farms and villages, woods and hedgerows have been laid out in the blink of an eye.

I cast my imagination 60 million years into the future. Like HG Wells' time traveller, I see the land and its wrinkled skin of green landscape blur and then dissolve.

What's left there is ocean.