Routes to Geomon – the A55
(note this route describes the road journey from Chester to Bangor using a dual carriageway. There is an alternative but very similar route by train. Unfortunately the TrawsCymru travel website says there is no suitable bus route!)
Leaving the border city of Chester our route follows the A55 dual carriageway (North Wales expressway) for a largely coastal journey to Anglesey. Initially on flat land floored by Irish Sea Till (formerly known as Red Northern Drift) with a reddish matrix from the Triassic rocks of the Irish Sea floor and erratics from anywhere north up to Scotland, the route climbs gradually. Past the complex junction at Ewloe, the road climbs onto the Carboniferous rocks of Halkyn Mountain – with extensive views out across the Dee Estuary to the Wirral – a promontory of Triassic Sandstone. The rocks here on Halkyn are principally limestone, with some metal (lead/zinc) mines. In places the limestone is stained red from iron seeping down from overlying New Red Sandstone rocks, long since eroded away.
Approaching Rhuallt the road suddenly descends steeply off the Clwydian hills to the Vale of Clwyd. The Clwydian range is and AONB which stretches all the way south to Llangollen and the Dee Valley https://www.clwydianrangeanddeevalleyaonb.org.uk/ . The Hills are underlain by Silurian rocks, principally sandstones and greywackes which are wonderfully exposed in the roadside cutting on the northern (right hand) side of the road going down the hill (beware, average speed cameras control this section of road).
Their western edge is a major fault (hence the very steep slope) which has dropped New Red Sandstones which floor the Vale of Clwyd down against the Silurian rocks. The AONB geology includes the Carboniferous limestone of Halkyn Mountain, and also the Egwyseg hills near Llangollen.
Having past St Asaph we approach the village of Bodelwyddan with its famous “marble church” – actually a very white form of Carboniferous limestone (sadly with age turning grey from pollution).
The road turns north and, skirting Abergele, reaches the coast. From here the hills reach down into the sea, cliffs of Carboniferous limestone, some big quarries
and at Llandulas, Reynes jetty (still in use) for exporting crushed rock. Note the view to the distance is the Great Orme, a huge headland of Carboniferous limestone.
Just before reaching Colwyn bay, the road cuts through an old coastal quarry and under ‘Rainbow Bridge’, a footbridge allowing pedestrian access to the coast.
Through the conurbation of Colwyn, views ahead are of coastal hills of limestone at Rhos-on-Sea and Little Orme’s head. Once clear of Colwyn the road crosses a broad flat low lying area between hills on either side. This is the original, pre-glacial, course of the river Conwy before a glacier blocked it and the river took over the glacial route directly out to sea to the west of the Great Orme’s Head.
Soon we come to junctions for Llandudno Junction, Betwys y Coed and Conwy.
Leave the A55 dual carriageway and follow the old road (this involves negotiating a few roundabouts but is well signposted) into Conwy crossing the river on a modern bridge (but note to your left two very historic bridges).
You are entering the The Castles and town walls of King Edward I World Heritage Site (www.cadw.gov.wales/visit/best-history/castles-town-walls-king-edward-gwynedd ) which includes Caernarfon, Conwy, Harlech and Beaumaris and demonstrates medieval military architecture at its most impressive. Built by Edward I (1272-1307) during turbulent times when the English king demanded submission of the Welsh princes, the scale of construction was unprecedented. The almost complete town walls at Caernarfon and Conwy demonstrate his plan to establish [and defend] English settlements.
As you cross the river, the castle looms up in front of you, perched on an outcrop of hard Ordovician sandstone. The town walls are complete, apart from modern piercings for road and railway, and you can walk almost all the way round the wall walk on top, gaining a bird’s eye view of the town layout and stunning views of the castle. Caernarfon may be the most magnificent, Beaumaris the most perfect design, but Conwy Castle is certainly the most romantic and impressive sitting on top of its rock overlooking the river and guarding the town. This castle is mainly constructed of the local hard dark grey sandstone but with red sandstone mouldings. As you explore Conwy, be sure to walk across Telford’s suspension bridge, a miniature version of Menai Bridge and marvel at Stephenson’s tubular railway bridge, lower but no less impressive than his Britannia Bridge across the Menai. Both are constructed from Carboniferous limestone. Exploring the castle, walking the walls, examining the bridges and visiting the ancient town houses (Plas Mawr, under the care of CADW, is amazing) will easily entertain you for a whole day.
You leave the town through a complete medieval town gate! Glance right to see the outside of a complete section of town wall. Follow the road till it joins the A55 dual carriageway.
The hills stretch right down to the coast, a string of granitic igneous intrusions from Conwy Mountain along to Penmaenmawr.
There are the remains of quarries all along this coastline, originally producing setts, cobblestone and curb stones for the booming industrial revolution towns of northern England;
The one remaining quarry produces crushed stone for railway ballast. The eastern edge of the Penmaenmawr intrusion, known as Graig Llwyd, is a famous Neolithic stone axe factory, the largest in Wales. The margin of the intrusion is chilled, very fine grained and almost glassy, breaking with a conchoidal fracture and perfect for making axeheads which were traded far and wide. If you turn off the dual carriageway into Penmaenmawr village you can drive down and park by the railway line, walk through an underpass out onto the coast fr omwhere there a excellent views back to the Great Orme and forward onto Penmaenmawr headland itself
The view seawards is across extensive sandflats at low tide to Beaumaris, with good views of the Carboniferous limestone outcrops at Penmon, Puffin Island and to what looks like another island, Great Orme’s Head, which is actually connected by a strip of very low-lying land on which Llandudno has been developed.
At Abergwyngregyn, a narrow valley cut by the river leads up to the famous Aber Falls where the river cascades down the edge of another granitic intrusion – a mile or so up a side road, then a wonderful walk up thevalley through ancient oak woodlands). The flat land to your right is a strip of Irish Sea Till (formerly known as Red Northern Drift).
Approaching Bangor you may catch sight of what looks like a Norman castle sitting atop a drumlin –
this is Penrhyn Castle (a National Trust property), constructed by the Penrhyn family from the proceeds of the Penrhyn slate quarries at Bethesda (and sugar plantations in the Caribbean) using Carboniferous limestone.
The dual carriageway coninues towards Bangor, looping round the south side of the town and approaches the Britannia Bridge to cross the Menai Strait to Anglesey.