Long before it was a sandy patch abutting Cardigan Bay, the beach near Ynyslas, close to Borth, Wales, was grassland—and before that, thousands of years ago, a forest. The proof is right there in the sodden sand, but it’s only fully visible every once in a while. And when it appears, it looks like something out of a fairy tale.

During times of strong wind and surging waves, layers of the wet sediment peel away, and clumps of sulfuric peat and stumps of long-dead trees emerge. They’re waterlogged, so the shin-high crags of ancient birch, pine, and oak look stained—dark brown, almost onyx when they’re wet. Hundreds, maybe thousands, of these stumps are scattered across a few miles of the shore, jutting through the sand in sharp, pointy angles. The size and shape often remind Martin Bates of shark fins.

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