Curious textures and patterns caused by weathering erosion in Devonian metasedimentary rocks at Porthmeor, St Ives, in Cornwall.
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Curious textures and patterns caused by weathering erosion in Devonian metasedimentary rocks at Porthmeor, St Ives, in Cornwall.
Is the pitting (I don’t know what else to call it) in photographs 4a, 5a, 6a, and 7a due to inclusions being washed or dissolved out? Whatever the cause, the effect is beautiful. Thanks for catching it.
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Hi, Linda, pitting is a good word to describe it. I don’t think the pits in these rocks from Porthmeor mark the place where there used to be small inclusions. The surrounding rock seems to be uniform in its fine texture without inclusions. There are fine layers because this rock (as far as my memory serves me) is metamorphosed slate. The pits are probably due to a mixture of natural chemical and physical abrasion. The exposed rock face was near-vertical. The pits were not so apparent on the flatter outcrops. The burst-bubble texture may relate to internal softer and harder constituents of the rock that have given rise to uneven erosion. The same kind of weathering texture, often on a much larger scale, is quite common on beachside rocks I have photographed, including a type of basalt on the Oregon Coast, and boulders at Chapman’s Pool in Dorset. In limestone rocks like those at Doolin Quay in Ireland and Spaniard Rocks in Gower, the flat surfaces often have distinct circular pits caused by dissolution from acid water (rain and/or sea).
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Wonderful colours and patterns in these rocks Jessica. I’ve visited this beach many times – I must examine the rocks more closely… !
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The few times I have visited Cornwall have demonstrated the wide variety of great rocks of which it is composed. I am very keen to return.
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I love Cornwall, it has such a beautiful rugged landscape. I never tire of it and I love the sea and all things related…
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Thank you, Evelyn.
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Thanks for the explanation of the pitting, I wondered too. Wow! I love the lacy look.
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Thank you, Claudia.
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