Yr Arddu
Encyclopedia
Yr Arddu is a mountain peak in Snowdonia
at 389 Metres high and situated approximately 2.5 Km south east of Beddgelert
village and just over 1 Km from the rather more famous mountain Cnicht
. It is a rugged hill with widespread rock outcrops and cliffs and as a consequence it is not commonly climbed. It is best approached by footpath leaving the minor road that links Nantmor
to Nant Gwynant
but the final 0.5 Km has no marked paths and can be a challenge at all times of the year.
The unusually craggy nature of the summit is due to the locally important geology. The Ordovician
period in Snowdonia was characterised by numerous volcanic eruptions although the volcanic peaks themselves have long since been eroded away. However, the outpouring or larvas and ash provide good evidence of this activity and Yr Arddu is a particularly good location to see the record of Ordovician vulcanism. The Yr Arddu Tuffs which are a sequence comprising the mountain are a sequence of predominantly welded acid ash-flow tuff
s in the outlier centred on Yr Arddu (North Wales). The tuffs accumulated above the Yr Arddu Fracture, which had previously influenced sedimentation. The heterogeneity of the tuffs and their restricted development suggest that they represent accumulations from small or suppressed (boiling-over) eruption columns in a submarine environment. There is evidence that indicates that the tuffs represent the earliest eruptive phase of the Lower Rhyolitic Tuff Formation.
The whole mountain is a designated site of special scientific interest
by the Countryside Council for Wales
.
A small lake, Llyn Yr Arddu, is located on the flanks of the mountain.
Snowdonia
Snowdonia is a region in north Wales and a national park of in area. It was the first to be designated of the three National Parks in Wales, in 1951.-Name and extent:...
at 389 Metres high and situated approximately 2.5 Km south east of Beddgelert
Beddgelert
Beddgelert, or in older English spelling often Bedgellert, is a village and community in the Snowdonia area of Gwynedd, Wales. It is reputed to be named after the legendary hound Gelert. Population 617.- History:...
village and just over 1 Km from the rather more famous mountain Cnicht
Cnicht
Cnicht is a mountain in Snowdonia which forms part of the Moelwynion mountain range.Its appearance when viewed from the south-west, i.e. from the direction of Porthmadog, has earned it the sobriquet the "Matterhorn of Wales". In reality Cnicht is a long ridge and, at 689 m, is the 5th highest...
. It is a rugged hill with widespread rock outcrops and cliffs and as a consequence it is not commonly climbed. It is best approached by footpath leaving the minor road that links Nantmor
Nantmor
Nantmor is a hamlet which lies about 1½ miles to the south of the village of Beddgelert in Gwynedd, North Wales.The current spelling of the name Nantmor is more modern most old documents from the 16th to the 18th century record the name as Nanmor, although the Ordnance Survey map of 1558 records...
to Nant Gwynant
Nant Gwynant
Nant Gwynant is a valley in Snowdonia, Gwynedd, north Wales. The A498 road descends into the valley in about two miles from Pen-y-Gwryd; it follows the Nant Cynnyd, the Afon Glaslyn and alongside Llyn Gwynant, then beside the Nant Gwynant river to Llyn Dinas and passing below Dinas Emrys to...
but the final 0.5 Km has no marked paths and can be a challenge at all times of the year.
The unusually craggy nature of the summit is due to the locally important geology. The Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
period in Snowdonia was characterised by numerous volcanic eruptions although the volcanic peaks themselves have long since been eroded away. However, the outpouring or larvas and ash provide good evidence of this activity and Yr Arddu is a particularly good location to see the record of Ordovician vulcanism. The Yr Arddu Tuffs which are a sequence comprising the mountain are a sequence of predominantly welded acid ash-flow tuff
Tuff
Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...
s in the outlier centred on Yr Arddu (North Wales). The tuffs accumulated above the Yr Arddu Fracture, which had previously influenced sedimentation. The heterogeneity of the tuffs and their restricted development suggest that they represent accumulations from small or suppressed (boiling-over) eruption columns in a submarine environment. There is evidence that indicates that the tuffs represent the earliest eruptive phase of the Lower Rhyolitic Tuff Formation.
The whole mountain is a designated site of special scientific interest
Site of Special Scientific Interest
A Site of Special Scientific Interest is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon...
by the Countryside Council for Wales
Countryside Council for Wales
The Countryside Council for Wales is an Assembly Government Sponsored Body. It is the Welsh Assembly Government's wildlife conservation authority for Wales...
.
A small lake, Llyn Yr Arddu, is located on the flanks of the mountain.