This is one of my favourite perched blocks, sitting on an ice-smoothed surface on one of the four tors of Carnedd Meibion Owen, above Ty Canol Wood. Some perched blocks have nothing to do with glaciation, but in this context glaciation is the only realistic explanation, since the large boulder cannot have dropped or slid from anywhere else.
It's dolerite, and has not moved far. But I think it was moved into position by glacier ice during the Devensian glaciation. This theory accords with the evidence of glaciation at Rhosyfelin, down in the valley below, and at Tafarn y Bwlch and many other localities up to the 330m contour. It's all piecing together into a coherent picture.
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