Conway, J. Geotrail along the South Stack coastline. GeoMôn Global Geopark Geowalk leaflet.
Geotrail along the South Stack coastline
Enjoy the magnificent Holy Island coastline whilst learning all about its fascinating geology on this beautiful and spectacular walk.
By Dr J Conway of Anglesey Geopark and Royal Agricultural College
The area around South Stack is a fascinating and beautiful stretch of coastline with not only amazing geology, but many examples of how it influences the landscape and land use. Not only does this Walk follow the coastal footpath within the AONB, but it also goes along a stretch of Heritage Coast that features in the Cybi Circular Walk (great care should be taken along the coastal path which sometimes lies above sheer cliffs and can suffer from strong winds).
The rocks here are some of the oldest in Wales, dating from the Cambrian to Precambrian Period some 500 to 550 million years ago. You will see three main rock types, quartzite, a hard white metamorphic rock formerly a thick deposit of sand; green schist, a banded and intensely folded metamorphic rock, formerly muds and silts on the sea bed; and dolerite, an igneous rock, squeezed into complex cracks within the schists, as a molten liquid, which now appears as a brownish weathering vertical dyke of rock along the cliff.
This trail starts from the junction of South Stack Road, and the land to the lighthouse grid ref
Now take the path through the RSPB carpark down to the coast and turn left again this is a dead end but the view along the coast towards the lighthouse is spectacular [stop 3]
Turn up the road towards the public toilets, sited in a small disused quarry [stop 4] where there is a clear exposure of a soil profile known as a podsol. This has a thin peaty surface accumulation of dead organic matter, over a pale greyish layer from which the iron has been leached [washed] out by organic acids, and re-deposited lower down as a thin rusty coloured layer [an iron pan]. Below the soil is the rock, frost shattered during the latter stages of the ice age. This soil underlies much of the South Stack Moor area, and being very acid and infertile has been ignored by farmers. It now constitutes one of the largest areas of maritime heathland in North Wales and presents a superb display of golden gorse and pink/purple heathers in spring and early summer.
Carry on up the road to the café and information point where you must purchase tickets (Easter to Sept.) if you intend to descend the steps and cross onto the small island bearing the lighthouse from where there is a spectacular view of folding in the cliffs.
The folding is not easily seen from here, so descend the stone steps and continue to Ellin's Tower [stop 5]
From here there is a good view of the sheer cliffs in the South Stack Formation, with folding and faulting controlling the appearance of the cliffs and presenting the birds with innumerable ledges for nesting.
Continue along the coastal path, climb the steps up to the road and walk along to the entrance to the lighthouse [stop 6]
While descending the steps, pause and look back along the coast to view some large scale folding. In spring, the cliffs are covered by nesting seabirds. Cross the bridge onto the island [stop 7]
Climb the steps back to the road, and then continue along one of the many paths leading towards Holyhead Mountain. The soils here are either podsols like the one in the small quarry, or more usually just a thin peaty layer over the rock. Most paths coalesce into a single path that skirts around the lower flanks of the mountain. You are now on the Holyhead quartzite [stop 8]
A path branches off to the right climbing to the summit