I can clearly see the ancient geological strata of Carboniferous and Devonian rock layers in my home country of Wales, particularly Pembrokeshire and the Gower!

I can clearly see the ancient geological strata of Carboniferous and Devonian rock layers in my home country of Wales, particularly Pembrokeshire and the Gower! So my layman theory would be that tectonics pushed these once horizontal layers nearer to the vertical, and that weathering processes eroded them slightly differently, giving each layer slight height differences that are imperceptible on most terrain colourshcemes, but Oilslick happily highlights. Hats off