Pen Cerrig-calch is a subsidiary summit of

Waun Fach Waun Fach is, with a summit height of , the highest mountain in the Black Mountains in south-eastern Wales. It is one of the three Marilyns over 600 m that make up the range, the others being Black Mountain and Mynydd Troed. To ...

in the Black Mountains in the

Brecon Beacons National Park The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain (range), Black Mountain ...

in southern

Powys Powys (; ) is a Local government in Wales#Principal areas, county and Preserved counties of Wales, preserved county in Wales. It is named after the Kingdom of Powys which was a Welsh succession of states, successor state, petty kingdom and princi ...

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

. Its summit, at a height of 701 m (2,300 ft), is marked by a

trig point A triangulation station, also known as a trigonometrical point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity. The nomenclature varies regionally: they a ...

. The peak sits high above the

River Usk The River Usk (; cy, Afon Wysg) rises on the northern slopes of the Black Mountain (''y Mynydd Du''), Wales, in the westernmost part of the Brecon Beacons National Park. Initially forming the boundary between Carmarthenshire and Powys, it fl ...

valley as it narrows above the small town of

Crickhowell Crickhowell (; cy, Crucywel , non-standard spelling ') is a town and community in southeastern Powys, Wales, near Abergavenny, and is in the historic county of Brecknockshire. Location The town lies on the River Usk, on the southern edge ...

. The views from here are wide-ranging and extend as far as the Beacons themselves to the west. A ridge runs off to the northwest and the shoulder of Pen Gloch-y-pibwr then turns north to the secondary top of

Pen Allt-mawr Pen Allt-mawr is a high subsidiary summit of Waun Fach and the third highest peak in the Black Mountains in south-eastern Wales. A very recognisable and prominent peak of the Black Mountains, it lies near the end of the more westerly of Wa ...

whose peak at 719m is also crowned by a trig point.

Geology

Like all of the hills in the Black Mountains, Pen Cerrig-calch is formed from mudstones and sandstones of the

Old Red Sandstone The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...

laid down during the

Devonian period The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

but it is unusual in having a band of

Carboniferous Limestone Carboniferous Limestone is a collective term for the succession of limestones occurring widely throughout Great Britain and Ireland that were deposited during the Dinantian epoch (geology), Epoch of the Carboniferous period (geology), Period. T ...

outcropping around the summit and giving rise to a few

shakehole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...

s. A classic example of an outlier, the name of the hill reflects this situation; it means 'top of the limestone rock' in

Welsh Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peop ...

. The actual summit itself is formed from pebbly sandstone of the

Marros Group The Marros Group is the name given to a suite of rocks of Namurian age laid down during the Carboniferous Period in South Wales. These rocks were formerly known as the Millstone Grit Series but are now distinguished from the similar but geograph ...

(formerly the Millstone Grit Series), which also dates from the

Carboniferous period The Carboniferous ( ) is a Period (geology), geologic period and System (stratigraphy), system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago (Myr, Mya), to the beginning of the Permian Period, ...

.
The rounded southwestern shoulder of the hill ends abruptly at a cliff by the name of Darren (

'edge') which was formed by a sizeable

landslip Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, ...

which most probably occurred in the early post-glacial period. There are many similar landslips in the Black Mountains, where weak strata have been eroded away, and destabilized the strata above. A large area of hummocky ground abounding with boulders of Old Red Sandstone lies across the slopes below Darren.

Archaeology

The most celebrated feature of the hill is the fortification of

Crug Hywel Crug Hywel is an Iron Age Celtic hillfort, with a clearly visible earth and stone ditch and rampart. Crug Hywel is approached by a couple of public footpaths across farmland from Crickhowell and Llanbedr and visited by the Beacons Way. It lies w ...

, a presumed

Iron Age The Iron Age is the final epoch of the three-age division of the prehistory and protohistory of humanity. It was preceded by the Stone Age (Paleolithic, Mesolithic, Neolithic) and the Bronze Age (Chalcolithic). The concept has been mostly appl ...

hillfort A hillfort is a type of earthwork used as a fortified refuge or defended settlement, located to exploit a rise in elevation for defensive advantage. They are typically European and of the Bronze Age or Iron Age. Some were used in the post-Roma ...

sitting atop a tilted mass of gritstone on the hill's southeastern spur and otherwise known as Table Mountain. However, there are also ancient cairns on each of the main tops. Small disused quarries once worked for the Old Red Sandstone are scattered across the hill's lower slopes.

Access

The upper parts of the hill are mapped as access land. Various footpaths approach the open access land from the

Usk Usk ( cy, Brynbuga) is a town and community in Monmouthshire, Wales, northeast of Newport. It is located on the River Usk, which is spanned by an arched stone bridge at the western entrance to the town. Usk Castle, above the town, overlooks th ...

Valley and from the valley of the Grwyne Fechan to the east. The

Beacons Way The Beacons Way (Welsh: Ffordd y Bannau) is a waymarked long distance footpath in the Brecon Beacons National Park, Wales. It is a linear route which runs for east to west through the National Park, and passes many of the most important lan ...

skirts the hill's southern and western slopes. The most popular route to the summit is the approach up the southeastern spur from

(Table Mountain).Ordnance Survey Explorer map OL13 'Brecon Beacons National Park: eastern area'

References

{{Reflist

External links

www.geograph.co.uk : photos of Pen Cerrig-calch and surrounding area
Black Mountains, Wales Mountains and hills of Powys Hewitts of Wales Nuttalls Crickhowell