Mynydd y Glog in the evening light - geograph

Mynydd-y-glog is a hill just east of the village of Penderyn in the northern corner of the county borough of

Rhondda Cynon Taff Rhondda Cynon Taf (; RCT; also spelt as Rhondda Cynon Taff) is a county borough in the south-east of Wales. It consists of five valleys: the Rhondda Fawr, Rhondda Fach, Cynon, Taff (Welsh: ''Taf'') and Ely valleys, plus a number of towns and vil ...

in south Wales. It lies within the Brecon Beacons National Park and Fforest Fawr Geopark. Its summit plateau rises to a height of 389m / 1277 ft at OS grid ref SN 982088, a spot marked by a trig point. To its north lies the partly dry valley of Pant Sychbant which forms the eastern extension of Cwm Cadlan. Its southern slopes are drained by various streams which feed into the Afon Cynon.

Geology

The hill is composed of a layer cake of rocks laid down during 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, ...

. Lowermost, and exposed along its shallow northern scarp, are Carboniferous Limestones whilst above these is the coarse Twrch Sandstone (formerly the 'Basal Grit') of the Marros Group (former ' Millstone Grit Series') also dating from the

. A number of northwest to southeast aligned faults runs across the hill. The limestone gives rise to

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

ic scenery including numerous

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. These occur on the gritstone area as well as the limestone.British Geological Survey 1:50,000 map sheet 231 'Merthyr Tydfil' & accompanying memoir

Archaeology

A number of ancient cairns are scattered about the slopes of Mynydd-y-glog.

Access

The hill is designated as open access and is freely available to walkers. A public footpath runs south-eastwards from the Cwm Cadlan road near Wernlas giving access from that direction. The hill can also be gained from the west via the former railway line at Penderyn and via the Natural Resources Wales's woodlands at

Penmoelallt Penmoelallt or Onllwyn is a hill in the northern part of the county borough of Rhondda Cynon Taff in south Wales. It lies within the Brecon Beacons National Park and Fforest Fawr Geopark. To its east lies the deep valley of Cwm Taf and to it ...

to the east.

References

External links

images of Mynydd-y-glog and surrounding area on Geograph website
{{coord, 51.7687, -3.4766, type:mountain_region:GB, display=title Brecon Beacons Fforest Fawr Mountains and hills of Rhondda Cynon Taf