The Community includes both Penderyn which is in the Geopark and Hirwaun which is not.

The lie of the land

Hirwaun Community ranges in height from 90m immediately west of Craig-y-ddinas (SN 911079) to 485m at Cadair Fawr (SN 978123).  other notable summits include:

• Penmoelallt at 420m (circa SO 003096)
• Mynydd-y-glog at 389m (SN 982088)
• Moel Penderyn at 371m (SN 938086)

The area is drained by the Taf Fawr to the east and the Afon Hepste and Afon Mellte to the west.  The centre of the area is drained by the Nant Cadlan which flows into the Afon Cynon.

Solid rocks

Hirwaun has a varied geology which in the north and east comprises rocks of the Brownstones Formation, the Plateau Beds Formation and the Grey Grits all of which are of Devonian age.

To their south and west are the younger Lower Limestone Shales, the Abercriban Oolite, the Cil-yr-ychen Limestone and Millstone Grit, all of Carboniferous age.  The sothernmost part of the Community is underlain by the Lower Coal Measures which include mudstones and a coarse sandstone known as the Farewell Rock.

All of these formations dip to the S or SE or in some areas the SW at between 5 and 25 degrees.

The rocks of the area are crossed by a series of geological faults running in the same direction as Cwm Taf.  A major fault at right angles to these is the Neath Disturbance.  Some tight folding of the local rocks is associated with this feature.

Legacy of the Ice Ages

Much of the area is plastered with glacial till.

Archaeology

There are numerous cairns and other features scattered across the upland parts of the area.

Maps

Geology

Sheet 231 ‘Merthyr Tydfil’ of the British Geological Survey’s 1:50,000 maps series of England and Wales gives full coverage of the Community.  Two versions are available – one showing the bedrock (or ‘solid’) geology and the other showing the superficial deposits (or drift’ geology) which overlie the solid rocks.  BGS publishes a 'memoir' to accompany these maps.

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.