475 million years old
Between 440 and 490 millions of years ago volcanic islands characterised the ocean which covered Wales in the Ordovician Period
The volcanic eruptions, mostly beneath the sea, gave rise to flows of lava rich in magnesium and iron.
As the extremely hot tongues of lava came into contact with cold sea water the outer surface hardened, forming a hard crust around the centre of liquid lava.
Then as the lava split, the blobs of lava piled up on top of each other, forming ‘pillows’
See the Rarities
Some of Wales’s rarest mountain plants grow on the mildly acid soils that developed on this lava. Our ‘Conserving Welsh Plants’ area, a short walk from the Stable Block restaurant, has a great display of these plants.
Strange But True
A very odd lichen grows on these rocks. Most lichens are made up of a fungus and an alga or bacteria. But the pink bull’s eye lichen Placopsis lambii has all three life forms in one body, and it produces strange red blobs when it fruits.
Where do the boulders come from? ARC Builth [Llanelwedd] Quarry, Powys