An Earthcache is a virtual cache designed to draw attention to and explain an interesting or significant geological feature. More details can be found at
www.earthcache.org
The coordinates given are for a car park and not the cache itself
N51° 51.171 W003° 50.501
This Earthcache relates to one of the more significant caves in the Western part of the Brecon Beacons National Park and within the Fforest Fawr Geopark.
Please note that caving/potholing requires
expert training, skills, knowledge and equipment.
Do not be tempted to go into
the cave unless you are an experienced and appropriately equipped
caver or you are accompanied by a certified Cave Leader from one of
the local caving organisations
(see the information at the end if this is something that appeals to you).
Ogof Foel Fawr & Ogof Pasg
Parking = N51° 51.171 W003° 50.501
Even though there are two names associated with the cave (Ogof)it is actually only one cave with two entrances! Each half was discovered separately in the 40's (Ogof Pasg/Easter Cave) and 50's (Foel Fawr/Cave of the large bare hill) and a connection linking the two caves was made in 1988 by Hereford Caving Club.
Having this configuration makes the cave quite unusual because it provides cavers with the opportunity to carry out a "through" trip where they do not have to retrace their steps to get out of the cave again.
Approximately half-way through the cave is a very narrow squeeze which resembles a "letterbox" - and to get through this slot requires that cavers remove their helmets because the slot is so narrow! (Not for the claustrophobic).
The entrance to Ogof Pasg (Easter Cave) can be found about half-way up the quarry face in the Herbert’s Quarry complex. It is not advised that cachers visit this cave entrance because it requires a scramble up a loose scree slope and dislodging boulders and debris is a real possibility. (Although a visit is not out of the question – it is not a requirement for successfully logging this cache).
However – cachers should visit Herbert’s Quarry to see the massively bedded (thick layered) Carboniferous Limestone in which the cave has formed. The limestone itself is a rock which was formed in tropical, “Caribbean-like” seas (in this case approximately 350 million years ago) and if one looks closely, it is possible to find marine fossils within the grey rock.
Sitting above the limestone (and towards the south) are the famous and younger Welsh coal-bearing rocks; to the north of the area are older rocks from the Devonian period.
During the Devonian period – the ancient landscape was hot and dry and probably even desert-like. These conditions gave rise to the formation of the red sandstone from which much of the Brecon Beacons landscape is composed. However, towards the end of that period – the land started to sink and the sea levels started to rise and under these warm tropical conditions, the limestone was deposited. Long after this the land rose again and water began to percolate through the limestone resulting in the cave you will be visiting.
When water (often carrying dissolved carbon dioxide from the air – which makes the water slightly acidic) works its way through small cracks and fissures in the limestone, the alkaline rock begins to dissolve. This causes the cracks to become larger and larger over time until they become passageways large enough for people to explore. This process takes many thousands of years to happen.
If the passageways form above the water table so that air is found in the passageway together with the eroding water – then often canyon or “key hole” shaped passages form (these are called “vadose” passages). On the other hand – where the passageways form under the water table so that there is never air in the passages (only the eroding water), rounded tube-like or “phreatic” passages will be formed.
The entrance to Ogof Foel Fawr however is much easier to visit and can be found above the car park on the main A4069 Llangadog to Brynaman road, on the steep ground to the East. Care must be exercised when visiting the entrance because there are small but significant cliff faces and sheer drops in this area where abandoned quarries now lie. Visiting when visibility is poor should only be under-taken with care and it is essential that children and pets are closely supervised., In addition, the ground on which the cave entrance lies is a steep grassy slope - so it gets quite slippery in the rain and stout walking boots are recommended.
The cave itself is mainly composed of “vadose” passageway (question 3) with a total length of about 830m (Cambrian Caving Council Registry data). It was formed like other caves by water slowly dissolving the limestone rock (made from the mineral calcium carbonate) away over tens of thousands of years leaving behind the explorable passages which twist and wind through the rocks.
Today the cave is home to a number of animals like Lesser Horseshoe Bats, the Herald Moth (Scoliopteryx libatrix) and a number of other insects and invertebrates.
(Please note that Lesser Horseshoe Bats are protected by European Law, and that to disturb them is a criminal offence, so if you happen to find one in the outer cave entrance then please leave it well alone!)
Back in the 1950’s cavers found a number of interesting bones in a location appropriately named “Bone Chamber” and these have been linked to animals living in this geographic area shortly after the ice sheets retreated – so in addition to its geological interest, the cave has a significant biological significance too.
A survey of the Herbert's Quarry cave is available on the Hereford Caving Club website and needs to be consulted to answer question four. (Many thanks to Hereford Caving Club for permission to include this link to their survey).
http://www.herefordcavingclub.org.uk/surveys.html
Suggested Route
1. Parking = N51° 51.171 W003° 50.501
2. Work your way towards the entrance of Ogof Foel Fawr by going first to =
N51° 51.170 W003° 50.399
then to N51° 51.140 W003° 50.381
then to N51° 51.144 W003° 50.337 (look for the sink holes here)
and finally to N51° 51.173 W003° 50.268 (the actual cave entrance)
3. Walk back down to the car park (take your time, remember the small cliffs and keep children/pets under control) and head
North/North East onto the Herbert’s Quarry cave road
=N51° 51.223 W003° 50.482
4. Follow the road N/NE past some abandoned quarry buildings until
you get to the actual quarry itself = N51° 51.250 W003° 50.070
5. The entrance to Ogof Pasg is towards the right of the quarry
face. Visiting this entrance is not advised and is not necessary to
successfully log this earthcache. (No coordinates provided).
WARNING -Please do not attempt going directly from the entrance of
Ogof Foel Fawr to Ogof Pasg because this could potentially take you
over the edge of the Herbert’s quarry cliff face. Follow the
suggested route – it is much safer and the views are
great!
To log this visit you should answer the
following questions
1. Between the time the cave was starting to form and the present day (fully formed and explorable) - suggest how the water table level might have changed in relation to the cave.
2. What are the main colours of the Herald Moth (Scoliopteryx libatrix)?
3. In relation to any cave – what does “vadose”
mean?
4. Looking at the Hereford Caving Club survey – approximately
in which direction is the “Bone Chamber” found in
relation to the Herbert’s Quarry floor or cliff face? [Look
for the two dolines above the word Herbert’s on the
survey]
5. Using your GPS altitude function – at what altitude is the
Foel Fawr cave entrance?
6a. (OPTIONAL TASK) Take a photograph of yourself holding your GPS next to the Foel
Fawr entrance of the cave – upload this in your log when you
record your visit.
6b. Estimate how wide the gap is in which the Foel Fawr cave entrance is located.
7a. Estimate the height of the Herbert’s Quarry cliff
face.
7b. (OPTIONAL TASK) Take a photograph of yourself or GPS with the Herbert’s
Quarry cliff face behind you - upload this in your log when you
record your visit.
You must NOT include the answers to these
questions in your log – please email the answers to me
separately using the email details associated with my profile
name. Logs without an accompanying email with the answers may be deleted.
***Congratulations to rhonddaroamers on being the FTF.***
Additional information on Herbert's Quarry(with thanks to Dyfed Archaeological trust)
The Black Mountain is recognised as a landscape of outstanding historic interest in Wales (Part 2 of the Register of Landscapes, Parks and Gardens of Special Historic Interest in Wales, Part 2.1 Landscapes of Outstanding Historic Interest. 1998. CCW, Cadw and ICOMOS UK ). It is also part of the Fforest Fawr Geopark, in recognition of the significance of its geology. Evidence of industries that have exploited the range of geological resources, since at least the Medieval period, survives over large areas of the Black Mountain.
From medieval times tenant farmers and cottagers surrounding the mountain had rights to quarry and burn limestone. These early workings consist of small quarries and "clamp" kilns which are still evident as small earthwortk features over large parts of the mountain. From the mid 18th century onwards agricultural improvers encouraged the use of lime to improve crop yields and lime production began to increase. The focus of this later activity is a large number and range of surviving 19th and early 20th century historic lime kilns, impressive quarries and a variety of other related features to the north of Foel Fawr.
The area, now known locally as Herbert's Quarry, was named after a recent owner dating back to the late 1930s, David John Herbert. The earliest documentary record of workings in this area dates to 1847. The quarry is shown on the 1st edition Ordnance Survey map (published in 1887) to include a series of at least eight lime kilns identified as "Pant y Ffynnon Limekilns", another group called "Craig y Nos and Blaen y Gwawr Limekilns", along with a further series of "Old Limekilns".
It appears that the quarry declined in use during the early 20th century and, following a final period of activity in the late 1940s, went out of use in the early 1950s.
Although the site is easily accessible to visitors and local communities, and many locals and tourists come to the car park to see the views, few are aware that they are surrounded by the remains of the mountain’s industrial heritage, on a road built for the transportation of mineral products, in a landscape shaped by the toil of generations of quarrymen.
The Brecon Beacons National Park Authoritywww.breconbeacons.org/
Hereford Caving Club http://www.herefordcavingclub.org.uk/
South Wales Caving Club http://www.swcc.org.uk/
British Caving Association http://www.british-caving.org.uk/?page=1
Cambrian Caving Council http://www.cambriancavingcouncil.org.uk/index.html
Black Mountain Centre, Brynaman http://www.brynaman.org.uk/index.html
Dyfed Archaeological Trust http://www.dyfedarchaeology.org.uk/
With sincere thanks to the Brecon Beacons National Park
Authority for authorising this Earthcache and my thanks to Hereford
Caving Club for permitting me to include a link to their survey of
the Herbert’s Quarry caves. In addition, my thanks to the
Black Mountain Centre (Brynaman) and Dyfed Archaeological Trust
References
British Geological Survey. Ammanford England and Wales Sheet 230.
McLeish, A. (1986) Geological Science. Blackie and Sons, Glasgow.
Toghill, P. (2003) The Geology of Britain: an introduction. Airlife Publishing.
