The high points include summits at East Prawle (443 m), Blackdown Rings at Loddiswell (580 m) and Stanborough Camp at Halwell (700 m). Between them and the sea lies 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 plethora of coombes scooped out out of red-brown Devonian soil and 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 the Pleistocene glaciations. 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 strata 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 there is an ocean.