Gaer (Black Mountains)
Encyclopedia
Gaer is the name of a hill in the Black Mountains
of the Brecon Beacons National Park in Monmouthshire
, south Wales
. It lies at the southern end of the long ridge between the valley of the Grwyne Fawr
and the Vale of Ewyas
one mile to the north of Bryn Arw
and 3 miles northeast of Sugarloaf. Its summit at 427m above sea level sits within an Iron Age
hillfort known as Twyn y Gaer.
which was laid down during the Devonian period. The southern slopes around Coed y Cerrig have been the subject of substantial landslipping in the past.
Black Mountains, Wales
The Black Mountains are a group of hills spread across parts of Powys and Monmouthshire in southeast Wales, and extending across the national border into Herefordshire, England. They are the easternmost of the four ranges of hills that comprise the Brecon Beacons National Park, and are frequently...
of the Brecon Beacons National Park in Monmouthshire
Monmouthshire
Monmouthshire is a county in south east Wales. The name derives from the historic county of Monmouthshire which covered a much larger area. The largest town is Abergavenny. There are many castles in Monmouthshire .-Historic county:...
, south Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
. It lies at the southern end of the long ridge between the valley of the Grwyne Fawr
Grwyne Fawr
The Grwyne Fawr is a river in the Brecon Beacons National Park in south Wales. A section of it forms the administrative border between Powys and Monmouthshire and also of the historic counties of Brecon and Monmouth. The river and its major tributary the Grwyne Fechan flow into the River Usk at...
and the Vale of Ewyas
Vale of Ewyas
The Vale of Ewyas is the steeply-sided and secluded valley of the Afon Honddu, in the Black Mountains of south Wales and within the Brecon Beacons National Park. As well as its outstanding beauty, it is known for the ruins of Llanthony Priory, and for several noteworthy churches such as those at...
one mile to the north of Bryn Arw
Bryn Arw
Bryn Arw is a hill in the Black Mountains of the Brecon Beacons National Park in Monmouthshire, south Wales. It lies 4 km north of the town of Abergavenny and 1.5 miles west of the village of Llanvihangel Crucorney...
and 3 miles northeast of Sugarloaf. Its summit at 427m above sea level sits within an Iron Age
Iron Age
The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...
hillfort known as Twyn y Gaer.
Geology
The mass of the hill is formed from the mudstones and sandstones of the Senni Beds formation whilst the upper slopes are formed from the sandstones of the overlying Brownstones Formation. Both are assigned to the Old Red SandstoneOld Red Sandstone
The Old Red Sandstone is a British rock formation of considerable importance to early paleontology. For convenience the short version of the term, 'ORS' is often used in literature on the subject.-Sedimentology:...
which was laid down during the Devonian period. The southern slopes around Coed y Cerrig have been the subject of substantial landslipping in the past.