Silurian Rock

430 million years old

These rocks were formed when turbulent clouds of pebbles, sand, silt and mud flowed down steep ocean slopes and settled as layers on the deep sea floor, as the strength of the currents, carrying the sediments waned. The eddy, caused by the strong current, created marks in the shape of a ‘V’ which you can see, and feel, on the surface of the layered rocks. The pointed end of the V faces the opposite direction of the current which created it.

 Spot the Birdy

Only a few lichen species grow on this quartz-rich sedimentary rock.

The golden shield lichen Xanthoria parietina is notable.

Its yellow colour is given by a chemical that acts as a sunscreen for the alga that lives within it. Where it grows in shaded places, it’s more grey than yellow.

It’s common on sea cliffs, farm buildings and trees in towns – places rich in nitrogen.

So why is it here?

Birds like to perch on these rocks and the lichen feeds on their droppings.

Where are the rocks from? ARC Ystradmeuny Quarry, Ceredigion