Mynydd Eglwysilan is a 355-metre-high
hill in the
Caerphilly
Caerphilly (, ; cy, Caerffili, ) is a town and community in Wales. It is situated at the southern end of the Rhymney Valley.
It is north of Cardiff and northwest of Newport. It is the largest town in Caerphilly County Borough, and lies wit ...
county borough in South
Wales 3 km to the south of
Nelson and a similar distance southwest of
Ystrad Mynach. To its south is
Senghenydd
Senghenydd ( cy, Senghennydd, ) is a former mining town in the community of Aber Valley in South Wales, approximately four miles northwest of the town of Caerphilly. Historically within the county of Glamorgan, it is now situated in the count ...
at the head of the
Aber Valley
Aber Valley is a valley community in Caerphilly county borough, South Wales. It has two main communities, Abertridwr and Senghenydd, which grew around the mining industry in the late 19th and early 20th centuries. Senghenydd has a longer histor ...
. Like neighbouring
Cefn Eglwysilan, the hill is named after the hamlet of
Eglwysilan Eglwysilan is an ecclesiastical parish and hamlet in Wales, within the community of Aber Valley in the unitary authority of Caerphilly County Borough.
History of the parish
During the 12th Century Norman invasion of Wales, the formal parish wa ...
4 km to the southwest, the church here being dedicated to an obscure Saint Ilan. Remains of a linear
earthwork known as
Senghenydd Dyke stretch across the southern side of the hill. It is considered to mark the edge of an extensive
13th-century deer park associated with nearby
Caerphilly Castle.
Geology
The hill is formed from the Hughes
Sandstone (formally the ‘Hughes Member’ and formerly the ‘Hughes Beds’) of the
Pennant Sandstone Formation
Pennant may refer to:
Flag or banner
* Pennon (or pennant), a narrow, tapering flag
** Commissioning pennant, the traditional sign of a warship, flown from its masthead while the ship is in commission
** Broad pennant, flown from the masthead ...
laid down late in the
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...
Period (c. 309–306 million years ago).
Siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...
s and
mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...
s appear beneath the main upper bed of sandstone.
Access
The summit area of the hill is mapped as
open access
Open access (OA) is a set of principles and a range of practices through which research outputs are distributed online, free of access charges or other barriers. With open access strictly defined (according to the 2001 definition), or libre op ...
under the
Countryside and Rights of Way Act 2000 thereby giving walkers freedom to explore it on foot. There are additionally a couple of
byways which traverse the eastern and southern margins of the summit plateau. The unfenced minor public road from Nelson to Senghenydd runs along the northwestern margin of the hill. A rough track passes by the
trig point which marks the summit.
[Ordnance Survey Explorer map 166 '' Rhondda & Merthyr Tydfil/Merthyr Tudful'']
References
{{reflist
External links
images of Mynydd Eglwysilan and area on Geograph website
Mountains and hills of Caerphilly County Borough