A part of the community of Yscir lies within Fforest Fawr Geopark, from the village of Cradoc southwards.

The lie of the land

The Community ranges in height from about 140m in the floodplain of the River Usk near Fenni-fach to 410m on Cefn Bola-maen outside of the Geopark.

Solid rocks

The underlying rocks are sandstones and mudstones which were laid down during the Devonian Period.  These rocks can be seen in the bed of the River Usk and on the slopes of Pen-y-crug.

Pen-y-crug and Fenni-fach and the other low hills which characterize the area are formed from sandstones of the St Maughan’s Formation and mudstones of the Raglan Formation.

Two major geological faults run SW to NE through the area. The Cribarth Fault runs to the south of Fenni-fach and Pen-y-crug and the Swansea Valley Fault runs through Cradoc.

Legacy of the Ice Ages

Surrounding hillsides are plastered with glacial till and moraines and relate to the presence of the major Usk Valley Glacier during the ice ages.

It is thought that the River Usk formerly flowed to the north of Brecon around the back of both Pen-y-crug and Slwch Tump in the vicinity of Cradoc and Llanddew.  Glacial action diverted it onto its present more southerly course, cutting the Llanspyddid gorge in the process.  Upstream of the gorge, a modern floodplain has developed and above which river terraces tell of earlier phases in the river’s development.

Archaeology

The Iron Age forts of Pen-y-crug and Y Fenni-fach occupy commanding positions above the Usk.  The remains of the Roman fort of Y Gaer (CICVCIVM) are visible too.

Maps

Geology

Sheet 213 'Brecon' of the British Geological Survey’s 1:50,000 map series of England and Wales gives full coverage of both the bedrock geology and superficial deposits of the Community.  BGS publishes a 'sheet explanation' to accompany this map.

General

The following Ordnance Survey maps cover the Community:

• Landranger sheet 160 'Brecon Beacons' (1:50,000 scale)
• Explorer sheet OL12 'Brecon Beacons National Park/Western area' (1:25,000 scale)

Public transport

Bus services operate along the road.

See Traveline Cymru for bus and train services including stops, timetables and route-planning information.