The Preseli Mountains (, ; or ), also known as the Preseli Hills, or just the Preselis, is a range of hills in western Wales, mostly within the Pembrokeshire Coast National Park and entirely within the county of Pembrokeshire.
The range stretches from the proximity of Newport in the west to Crymych in the east, some in extent. The highest point at above sea level is Foel Cwmcerwyn. The ancient of track along the top of the range is known as the Golden Road.
The Preselis have a diverse ecosystem, many prehistoric sites, and are a popular tourist destination. There are scattered settlements and small villages; the uplands provide extensive unenclosed grazing, and the lower slopes are mainly enclosed pasture.
Slate quarrying was once an important industry. More recently, igneous rock is being extracted. The Preselis have Special Area of Conservation status, and there are three sites of special scientific interest (SSSIs).
Name variations
A peak is spelt Percelye on a 1578 parish map, and more recent maps show the range as Presely or Mynydd Prescelly. The etymology is unknown, but is likely to involve Welsh prys, meaning "wood, bush, copse". A number of other peaks are shown on the 1578 map, but the only other named peak is Wrennyvaur (now Frenni Fawr). An 1819 Ordnance Survey Map refers to the range as Precelly Mountain (singular). An 1833 publication stated: the ancient Welsh name...is Preswylva, signifying "a place of residence", but does not cite any evidence. 21st century maps show the range as Mynydd Preseli.
Geology
The hills are formed largely from the Ordovician age marine mudstones and siltstones of the Penmaen Dewi Shales and Aber Mawr Shale formations which have been intruded by microgabbro (otherwise known as dolerite or diabase) of Ordovician age. The former slate quarries at Rosebush on the southern edge of the hills worked the Aber Mawr Formation rocks whilst it is the dolerite tors of Carnmenyn which have been postulated, amongst other localities, as the source of the Stonehenge ‘bluestones’.
In contrast Foel Drygarn towards the eastern end of the range is formed from tuffs and lavas of the Fishguard Volcanic Group. Further east is Frenni Fawr which is formed from mudstones and sandstones of the Nantmel Mudstone Formation of late Ordovician Ashgill age. The sedimentary rocks dip generally northwards and are cut by numerous geological faults. Cwm Gwaun is a major glacial meltwater channel which divides the northern tops such as Mynydd Carningli from the main mass of the hills.
Geography
The hills, much of which are unenclosed moorland or low-grade grazing with areas of bog, are surrounded by farmland and active or deserted farms. Field boundaries tend to be earth banks topped with fencing and stock-resistant plants such as gorse. Rosebush Reservoir, one of only two reservoirs in Pembrokeshire, supplies water to southern Pembrokeshire and is a brown trout fishery located on the southern slopes of the range near the village of Rosebush. To the south is Llys y Fran reservoir. There are no natural lakes in the hills, but a number of rivers, including the Gwaun, Nevern, Syfynwy and Tâf have their sources in the range.
Peaks
The principal peak at above sea level is Foel Cwmcerwyn. There are 14 other peaks over of which three exceed .
Settlements
Villages and other settlements within the range include Blaenffos, Brynberian, Crosswell, Crymych, Cwm Gwaun, Dinas Cross, Glandy Cross, Mynachlog-ddu, New Inn, Pentre Galar, Puncheston, Maenclochog, Rosebush and Tafarn-y-Bwlch. The only town in the Preseli area is Newport, at the foot of the Carningli-Dinas upland in the northwest of the range.
Natural history and land use
The Preselis provide hill grazing for much of the year and there is some forestry. As well as features of interest to geologists and archaeologists, the hills have a wide variety of bird, insect and plant life. There are three sites of special scientific interest (SSSIs): Carn Ingli and Waun Fawr (biological), and Cwm Dewi (geological). The Preseli transmitting station mast, erected in 1962, stands on Crugiau Dwy near the hamlet of Pentre Galar. To the south of Crugiau Dwy is the extensively quarried hill Carn Wen (Garnwen Quarry) which was still actively extracting igneous rock in 2018.