THE BOOK
Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click
HERE

Saturday, 16 January 2021

A stony silence......

 

 

Another piece of ancient history -- from the Western Mail coverage of the Millennium Stone pull in the summer of 2000.  This was the first glitch, after just one mile of pulling; after this, all the pulling was on asphalt roadways, with the assistance of low-friction netting.  There were of course other glitches as well, culminating in the loss of the stone onto the bed of Milford Haven.   It was not experimental archaeology's greatest success........

The drama is recounted in the pages of my book.



Friday, 8 January 2021

Gas explosion craters in permafrost



This is an interesting article from the BBC web site:

https://www.bbc.com/future/article/20201130-climate-change-the-mystery-of-siberias-explosive-craters

It describes a series of craters formed in Siberia, where a rather unique combination of factors in the permafrost layers causes a buildup of methane gas trapped beneath the surface frozen layer, and then an explosion which leaves a spectacular steep-sided crater behind.  Some of the explosions are accompanied by flames and smoke.  There are no observations of a natural explosive methane gas event actually happening, but as the permafrost continues to melt, there will be more and more of them.......

Wednesday, 6 January 2021

The Preseli Tors


Foel Drygarn
Carn Afr

When we think of tors, we think of Dartmoor and granite, and of spectacular masses of rock standing on a hill summit on the skyline.  Reality is, of course, more complicated.  A tor is a residual, wart-like mass of bare bedrock rising conspicuously above its surroundings from a basal rock platform generally buried by broken or weathered debris.  Tors are landforms of differential weathering and erosion which occur in all climatic zones on Earth.  Only in formerly and presently glaciated regions are tors rare and here these often delicate rock structures have been largely swept away by glacial erosion, especially on hillsides affected by streaming ice.  Where tors do survive, their significance has prompted debates which stretch back over 50 years relating to ice limits, glacier basal thermal regime, depths of glacial erosion and the origins of the tors themselves.  In West Wales tors come in many shapes and sizes, although they are normally associated with outcrops of igneous rock.  Almost all of them have been affected by glacier ice at some stage or other.

This is a small glossary of the main tors, mostly on the Preseli upland ridge -- extracted from the manuscript of a book that I never did get round to publishing........  But watch this space for news of a new publication before too long!

I will enhance this post by adding photos as appropriate.   This post (6 January 2021) is a republication -- with additions and corrections -- of the post first published in December 2016.

On the satellite image below we can see the locations of "the eastern tors" including Foel Drygarn, Carn Meini,  Carn Goedog and Carn Alw.





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Up Among the Preseli Crags


Carn Afr

Grid Ref SN092302.    Alt 380m.        This is a very beautiful tor on the southern flank of the Preseli ridge, only a couple of kilometres away from the hamlet of Rosebush and almost due south from Foelcwmcerwyn summit. Its name can be translated as "the cairn of the goat". It is a hillside tor (rather than a summit tor) at an altitude of 380m, and it looks down upon a shallow depression and then over the "step" of Mynydd Crwn. The main feature of the tor is a prominent double pinnacle of rock which is visible from a great distance. Around it there are small vertical cliffs, grassy steps and clean slabs of rock, with a litter of massive boulders especially to the west. There are several perched boulders near the pinnacle. The rock is for the most part rhyolite, but there are also other foliated or layered volcanic rocks including tuffs and trachyte lava.  This is the only substantial tor on Preseli which is made of volcanic rocks belonging to the Sealyham Volcanic Formation; all the others are made of rocks belonging to the Fishguard Volcanics. There is only a little scree, at the foot of the lowest of the cliffs. The tor is reminiscent of Plumstone Rock, and it is deeply weathered.  It look as if it has been battered by the elements since the beginning of time....... But the lower part of the rocky slope has abundant ice-smoothed outcrops indicative of ice action, with an upper edge around 365 m. 

 Just beneath the pinnacle there is a clean grassy bank which is perfect for a summer picnic or even an overnight camping stop. Beneath the tor there is a wonderful old sheepfold, and to the east a long-since abandoned rectangular enclosure with six small fields and a ruined cottage and garden. Not much is known about its history. A short distance to the SW there are also traces of a "ty unnos" cottage and garden on the edge of the common.  The tor is best approached across the common from the bridle path which runs along the south-eastern flank of Pantmaenog Forest.

Carn Afr and the nearby sheepfold -- satellite image.  The old farm enclosure (now abandoned) is a couple of hundred metres to the east of the crag. 

Oblique aerial photo from the RCHMW web site.  The tor is at top left, and we can see the enclosed area that shows the site of an ancient settlement.

The "twin towers" or pinnacles which look down on the other rocky outcrops of the hillside tor at Carn Afr.  They are made of varied volcanic rocks of Ordovician age.

Carn Afr -- complex flow structures and cavities in the lava.

One of the ice-smoothed outcrops at the base of the slope at Carn Afr.



Carn Alw 

Grid Ref. SN138 337.   Alt 240m.       The largest and most spectacular tor in the whole of the Preseli area, standing in glorious isolation above the sweeping grasslands on the northern flank of the main upland ridge. Translated, its name is "echoing rock" or "calling rock". Its summit is only about 240m above sea-level. It is most easily reached from the roadside near Ty Coch or from Mirianog Ganol. Its northern and eastern faces are high, shadowy and forbidding, but the approach is easy from all directions. It is made of light-coloured volcanic rocks including dolerite, rhyolite, felsite and various others with complicated names. Look at the glassy texture and "flow structures" in some of the rock outcrops, formed while the rock was cooling from the molten state. About 400 million years ago this was clearly a major centre of volcanic activity; perhaps it developed as a subsidiary eruption cone on the flank of the much larger Foeldrigarn volcano. Some pieces of rock from here were assumed by HH Thomas to have found their way to the "bluestone circle" at Stonehenge; probably they were eroded by ice moving along shear-planes in the Irish Sea Glacier as it crossed the upland ridge, and were later dumped when the ice melted not far from the famous and enigmatic monument. (Note: Thomas's work has been questioned by more recent geological research.)  There are many beautifully ice-moulded surfaces on the tor, and also traces of glacial grooves and crescentic gouges..   

The most interesting feature of Carn Alw today is the small Iron Age fort located on its western flank and summit. Like some of the Norman castles of Pembrokeshire it has an "outer bailey" and an "inner bailey"; the former was the main settlement site, with traces of old hut circles still to be seen; and the latter, just beneath the summit, was the last defensive position that could be occupied if the outer defensive walls were breached by an attacking tribal army. The old defensive ramparts and portal are still visible, as is a wonderful "chevaux de frise" beyond them. This feature, very rare in Britain, was built to prevent cavalry attack and was made of pointed stones (and probably sharp wooden stakes) angled into the ground and set close together. Out on the moorland to the south-east there is a fine walled enclosure (now somewhat ruinous) probably used by the Carn Alw Iron Age community, and also other cairns, walls and man-made stream channels of similar age. There is a charming fairy story associated with this carn and a nearby farm (now lost) called Llech-y-deri. The hero of the story is a young man who was taken to fairyland after succumbing to the "enchanted music" of the fairies which he heard echoing around the rock; perhaps this is where the name "Carn Alw" comes from.

Carn Alw and the surrounding area were used as "doubles" for the 1982 Battle of Tumbledown that occurred during the Falklands War, during the making of a TV drama of that name.  The controversial drama (shown in 1998) starred Colin Firth, and established him as one of the stars of British TV.

Carn Alw, with Foel Drygarn in the distance

Carn Alw

Carn Alw

Carn Arthur 

Grid Ref SN134 322.     Alt 300m.        This tor is perched on the mountain side, looking down on the open depression of Cors Tewgyll and across to the crags of Carnmeini (Carn Menyn). The local rock here is coarse dolerite, and there are some outcrops which show the large while felspar crystals which are characteristic of spotted dolerite or bluestone. The rocky outcrop is easily approached from above, where there is a grassy platform close to a huge perched boulder. This massive block -- and possibly one or two others lower down on the outcrop -- were assumed by the locals to have been placed there by King Arthur or some other mighty hero. Less romantically, we now know these rocks to be nothing more than large glacial erratics left by retreating ice. The tor is in an advanced state of decay, with a great litter of broken blocks and scree banks on its lower part. Not far away is Bedd Arthur, reputed to be one of the burial places of the mysterious king (I suppose this location has as good a claim as any other).

Carn Arthur


Carn Arthur and the famous perched boulder

Carn Bica 

Grid Ref SN129 325.   Alt 380m.       This little tor would be called "pointed carn" or "peaked carn" in English, in recognition of its conical shape. It is located on the axis of the Preseli summit ridge.  It is not a very prominent feature, and has suffered from a great deal of frost shattering in the Ice Age, and also from comprehensive rearrangement by the Bronze Age folk who built a large burial mound on its flank. The mound of loose stones has since been further rearranged by various members of "Dad's Army" who manned a lookout post here during the Second World War; and by assorted boy scouts and cadets trying to make shelters from the wind and the rain in this bleak and exposed spot. Note that the rock here is classic spotted dolerite -- the rough surface texture of boulders is characteristic, and on broken fresh surfaces the large white crystal clusters are very noticeable. This cairn is close to the route of the Bronze Age "Golden Road", and about 100m to the east you can see the strange stone arrangement referred to by the locals as Bedd Arthur or "the grave of King Arthur." The wooden posts close to the carn mark part of the route of Ras Beca, the tough fell trace which takes place in these hills in August each year.

Carn Bica -- late winter sun

Carn Breseb 

Grid Ref SN136 332.   Alt 1050 ft.    This carn (translated as "manger rock") is a substantial outcrop of spotted dolerite on the northern flank of the upland ridge, at an altitude of about 300m. In reality there are several stepped outcrops here, all of them very much degraded because of frost shattering and the downslope movement of blocks and scree. The tor does not look much like a manger, but the name may indicate that the local farmers once used to feed their animals here. The most prominent feature of the carn to be seen from a distance is the flat slab which looks like a gigantic needle when seen end-on. There is a large area of broken rock (and some solid rock) here, and it is fascinating to explore the nooks, crannies and crevices and to discover the sheltered and nutrient-rich "micro-environments" which provide homes for lichens, liverworts, and higher plants in this otherwise hostile and open terrain. There are traces of very ancient stone walls on the north-eastern flank of the carn, suggesting that it may have been used by the Iron Age inhabitants of nearby Carn Alw. 

Carn Breseb
  

Carn Ddafad-las

Grid ref SN147 329.  Alt 325m.  There is not much left of this little tor, which can be named "the cairn of the blue sheep" in English. Goodness knows where its name comes from; perhaps there was once a prehistoric sheep farmer here who marked his sheep with blue dye made from bilberries! It is one of a group of little tors around the same altitude,  just to the north of the Golden Road track and close to Carn Gyfrwy. Frost shattering, and possibly the action of overriding glacier ice, have damaged the tor so badly that it now consists simply of a rickety pile of massive boulders. One feels that the whole thing could collapse at any moment, so if you explore this tor and climb on it, please employ great caution.

Carn Ddafad-las


Carn Ddu-fach

Grid Ref SN151 332.  Alt 970 ft.  The name means "little black cairn".   A small dolerite tor on the broad upland ridge, located almost midway between Foel Drygarn and Carn Ddafad-las.  It's accessible across the heather moor via assorted sheep tracks.  There are two main outcrops, separated by a grassy bank.  

   
Foel Eryr 

Grid Ref SN 068 231.  Alt.           There is no real tor here -- just a few rocky outcrops of dolerite, and a jumble of rocks on the hillside which is so substantial (across an area of c 100m x 100m) that we can refer to it as a destroyed tor. In that respect it's very similar to the feature in Cwm Cerwyn called Craig y Cwm.  Below the broken rock area (on a SE-facing hillside) there is a grassy bench with some small hummocks on it, and it may be that these are small morainic remnants left by a lobe of ice that pressed through the Bwlch Gwynt col at the height of the last glaciation.  The altitude of these features is 1400 ft, which is exactly the altitude at which a thin veneer of till on the hillsides hereabouts gives way to broken bedrock.  Whatever the origins of this rocky wilderness, it is quite intriguing and attractive as a landscape feature.  On the Foel Eryr summit itself, adjacent to the Bronze Age burial mound, there are rocky outcrops and a boulder stream running westwards, but no trace of a tor.  But there are abundant traces of rock collection -- a vast quantity of stones up to 50 cm in diameter was needed for the construction of the "tumulus".

Foel Eryr -- all that''s left of what might once have been a tor.



Carn Fach 

Grid Ref SN 080 326.  Alt 1275ft.        There are no tors worth the name to the west of the Haverfordwest - Cardigan road, but there is a small one just to the east of the road as it drops down from Bwlch-gwynt towards Tafarn y Bwlch.  In fact there are several small crags here, made of flinty and slightly speckled dolerite.  This was one of the locations used in the making of a TV series called "Homeland", featuring Anthony Hopkins.

Looking towards Carningli from Carn Fach.

Ice-smoothed slabs on the denuded tor of Carn Fach.

Carn Gaseg

Grid ref SN160 328.  Alt 1000 ft.    This is a small tor south of Foeldrigarn and the Golden Road. It is on private land and like Carn Sarn is therefore difficult to visit; but there are similar small tors (Carn Goi, Carn Pant-teg, and Carn Bwdcyn being the only named ones) in the coniferous woodland to the west. They are made of dolerite and other volcanic rocks. Before the woodland was planted there were two smallholdings in the neighbourhood, now reduced (like many others around the flanks of the uplands) to tumbled cottage walls and a few traces of paddocks and kitchen gardens. When you approach Carn Gaseg from the north you may feel that it does not look very interesting; but you would be mistaken, for when you drop down over the brow of the hill you encounter several splendid rock bastions up to 6m high. When seen from downslope the tor is very spectacular, and very beautiful. Most of the dolerite rock faces overlook a grassy terrace of bedrock slabs with patches of gorse and heather. Some of the slabs appear to have been smoothed by the action of overriding ice. The dolerite here is fine-grained and in places flaky. There are a few elongated stones which have been broken from the solid rock by frost action, and the tor is still breaking down, with long deep cracks, gullies and perched blocks.

Carn Gaseg, seen from the road below.  It's on private land, and the owner does not encourage visits!

The tor is very close to this gate, but you'll have to give it a miss. 


Carn Goedog

Grid Ref SN128 333.  Alt 300m.   This is one of my favourite Presely tors, partly because of its impressive size and partly because it is a tranquil place, seldom visited by hill walkers. Located on the northern flank of the upland ridge, it is adjacent to the old drover's route used by many thousands of animals en route from Pembrokeshire farms to the meat markets of the Midlands and London in the 1700's and early 1800's. The up-slope flank of the tor (at about 300m) is not very prominent, but on the downslope side there is a wilderness of huge dolerite blocks, banks of scree, little grassy platforms, solid rock outcrops, crevices and caves. The rock is very coarse, with some spotted dolerite. One or two small trees have managed to survive here in places inaccessible to grazing animals; but the name ("woodland cairn" in English) indicates that there must once have been an extensive woodland here after most of the upland ridge had been cleared by burning, felling and grazing. Recently the tor has attracted attention following the suggestion by geologists Richard Bevins an Rob Ixer that many of the Stonehenge spotted dolerite monoliths have come from here. However, there are no perfect matches between any of the Stonehenge and Carn Goedog rock samples. Prof Mike Parker Pearson and colleagues claim that there is a Neolithic "bluestone quarry" here; but intensive investigations (reported on this blog) have revealed no unequivocal signs of quarrying in prehistoric times, and indeed the radiocarbon evidence from the site suggests nothing more than intermittent visits by hunters and travellers over many millennia..

On the gentle slope beneath Carn Goedog, on the north flank, there are traces of hut circles which were thought until recently to date from the Bronze Age.  However, investigation by Dyfed Archaeology has shown the remains of simple buildings to be much more recent -- and possibly inhabited in the Middle Ages.


Carn Goedog

Carn Goedog -- broken crags affected by frost and overriding ice

Carn Gwr 

Grid Ref SN142 330.  Alt. 315m.    This name means "husband's cairn" or something similar.  The name suggests that from a distance,  a man might be standing on the summit. There are really five separate small tors here, scattered about on a broad saddle or col in the upland ridge at an altitude of c 315m. There are no steep slopes, and it is easy to stroll between one tor and another on the heather and bilberry moorland. Here you are right at the heart of "bluestone country", with tors all around you. Carn Bica, Carn Breseb, Carn Alw, Card Ddafad-las, Carn Gyfrwy, Carn Meini and Carn Arthur are all within easy walking range. As you walk around this area, with skylarks above and sheep and mountain ponies grazing on the moorland, you can feel the timeless serenity of Presely; and you can also see traces everywhere of human occupation of this landscape over 3,500 years or more. Slight ridges in the turf, pits, elongated hollows, fallen stone walls and small stone cairns may date back to Bronze Age or Iron Age times. An old cart track runs across the moorland here, linking the rock outcrops with the farming community to the north which used the area as a handy quarry for gateposts and other "special stones". The cart track, in places deeply entrenched, runs downslope between Carn Breseb and Carn Alw and then to the west of Carn Alw down towards Mirianog Ganol.

Carn Gwr


Carn Gyfrwy 

Grid ref SN 147 327.  Alt 365m.     One of the most prominent features on the Presely ridge, this cairn is more of a rock bastion than a tor. It is made of spotted dolerite or bluestone, and has a steep cliff face at its northern end, immediately overlooking the route of the ancient Golden Road. Its summit is about 365 m above sea-level. On the OS 1:25,000 Outdoor Leisure Map the place-name is incorrectly located; the name means "saddle cairn" in English, and there is no doubt which cairn has the saddle-like appearance. There is another error in the labelling of the so-called "sheep-fold" beneath the cliff face. This crude stone-walled enclosure has also been referred to in the literature as a "drover's hut." However, it is far too small to contain sheep, and it is some way from the old drover's route. It is more likely to be a simple shepherd's shelter used during bad weather. It is still used for this purpose by weary hill walkers caught out in the wind and rain.

Carn Gyfrwy

The enigmatic stone-built shelter at the northern tip of Carn Gyfrwy, adjacent to the Golden Road.


Carnau Lladron

Grid ref SN 013 331.  Alt    .   A series of beautiful small crags and a great litter of boulders on the northern flank of the Preseli ridge, a very long way from everywhere.  One of the loneliest spots in the uplands.  It's just over 1km from the deserted "hafod" (summer grazing) settlement of Hafod Tydfil.

Carnau Lladron

Carnau Lladron

Cerrig Lladron

SN 068 322.  Alt.  .  A small and jagged outcrop of crags and boulders on the flank of Foey Eryr, a short diatance to the NE from the burial mound on the summit.  It's easily accessible from the footpath, on the open common.  There was once a larger tor here, but it has been heavily denuded, partly by ice action, so that there are nows several detached segments and even a few "outliers"of rock pinnacles sticking out through the turf. The main outcrop consists of several massive boulders in a precarious position. On one of the outcrops there are clear traces of moulding by overriding ice.

Cerrig Lladron

Cerrig Lladron -- one of the outlying pinnacles. Sometimes mistaken for a pair of standing stones......


Carn Llwyn

Grid ref SN 090 367.  Alt.  .   Not one crag, but several, more or less lost in the gnarled oak woodland of Ty Canol, not far from the tors of Carnedd Meibion Owen.  The crags are made of various volcanic rocks -- and they are very different from the tors on the hillside above. The summits are difficult to climb because of gorse and brambles, but if you are brave enough to get to the topmost summit, you will be rewarded with spactacular views.   You might even find the "Druid's Cave" which probably had nothing at all to do with the druids -- but it was used as a hideaway by Simon Hughes, a local man who was a Quaker conscientious objector during the First World War.  He was hunted by the Army, but was never captured, and after the War he was allowed to get on with life without any retribution from the authorities.

Carn Llwyn, almost lost in the trees.......

Some of the tumbled slabs near the cave on Carn Llwyn

Some of the inscriptions on a slab inside the cave.


Carnedd Meibion Owen

Grid ref  SN 092 365.  Alt. .   A series of spactacular and beautiful crags of dolerite, located on a spur some way to the north of the main Preseli ridge.  The rocks are quite close to the famous oakwood of Ty Canol.  From the summits you can look down towards Cilgwyn with Carningli and the sea in the distance.   Access is very easy, along a footpath leading from a parking area on the minor road to Brynberian.  There is a famous perched erratic on one of the crags, and this may have encouraged a local legend that the four rocks are the petrified remains of the last giants to have lived in this neighbourhood.

Maytime beneath the lowest of the Carnedd Meibion Owen crags.

Carnedd Meibion Owen

Perched block on one of the tors at Carnedd Meibion Owen


Carn Meini  or Carn Menyn

SN 144 325.  Alt.  .   Carn Meini or Carn Menyn is the one Presely cairn whose name is known to people from all over the world, since it is reputed to be the source of some of the famous Stonehenge spotted dolerite bluestones.  (Its reputation is largely undeserved, since recent geological work suggests that the said bluestones have probably come from other locations.) The single name is used to describe a cluster of seven or eight distinct tors arranged in an arc around a spur on the upland ridge. They are very spectacular indeed, and from a distance they give the skyline a jagged or "cock's comb" appearance. The name is interesting. In English the name Carn Menyn (used on recent OS maps) would be "butter cairn", but this is a nonsense name in this geographical setting, unless there was an association with butter-making on a "haft" or summer farm.  It is much more likely that the alternative Carn Meini ("cairn of the stones") has the better historical claim. Also, the words "maen" (singular) and "meini" (plural) are used in the context of shaped or dressed stone, as in "maenhir" ("long stone") used by the old archaeologists as a word for a standing stone. We may speculate therefore that the name was first used to describe a place of special elongated stones; and indeed there are many elongated stones here as a result of crude columnar jointing in the spotted dolerite. The massive tumbled blocks which are characteristic of this area indicate that there has been large-scale frost shattering here during periods of prolonged cold climate; but there are also some wonderful ice-smoothed surfaces at the southernmost edge of the rocky spur, with deep gullies and cliffs which indicate that over-riding glacier ice has "plucked" or dragged away large quantities of broken rock. The rock fragments, some of them weighing several tonnes, were carried up into the body of the glacier along shear-planes as it flowed southwards and south-eastwards, to be dumped hundreds or even thousands of years later on the fringes of Salisbury Plain. There are a number of possible man-made features among the Carn Meini tors. For example the flat stone referred to as the "altar stone" may be a sub-Neolithic burial chamber or cromlech, and there are a number of traces of very old stone walls that may date back to the Iron Age. An ancient cart-track is cut into the hillside between two of the eastern tors; it runs down to the road near Glanrhyd, and was used by farmers who were collecting convenient elongated stones from the mountain for use as gate-posts, lintels, steps or sills.


Carn Meini
  
The extensive crags of Carn Meini, in an oblique air photo
Ice-smoothed slabs at Carn Meini -- clear evidence of glacial erosion

Carn Pant-teg

Grid Ref SN 153 327.  Alt.  .  Another small tor in a tumbledown state, surrounded by modern forestry, south of the Golden Road footpath and on private land.


Carn Sarn

Grid ref SN 159 327.  Alt. .  Literally this means "causeway cairn", and indicates an alignment of rocks. This little tor is almost due south of Foeldrygarn and is on private land to the south of the Golden Road.  Access is not encouraged by vhe lndowner!   The causeway or route remembered in the name may be the Golden Road itself, since it has been used by traders and local inhabitants over a period of at least 4,000 years. The tor is part of the same volcanic complex as Carn Meini and Carn Gyfrwy; and other small tors are now lost in the coniferous plantation of Llethyr-mawr. The tor is not very spectacular, consisting of little more than a few dolerite outcrops on the hillside and a few small pinnacles up to 3m high. There are broken boulders scattered across the slope, over an area of about 50m x 50m. There are grassy banks and patches of gorse and heather, and this is a pleasant sunny place sheltered from westerly and northerly winds.


Satellite image of Carn Gaseg (above) and Carn Sarn (below).

The Carn Sarn outcrops.  The forest plantation is just to the left of the photo.


Carn Sian

Grid Ref SN 128 322.  This little dolerite tor, almost in the centre of the Talfynydd upland spur, is named after someone called Sian or Jane. It is unremarkable as tors go, but well worth a visit since the walking is easy hereabouts, and there are fine views towards Carn Meini and Foeldrygarn. The land surface in the vicinity of the tor has been greatly modified by the hand of man. If you look carefully you will see the traces of old stone walls and enclosures which probably date back to the Bronze Age or Iron Age. There are many elongated hollows which show us the routes of ancient trackways. And the turf is pock-marked with long-abandoned peat cuttings, reminding us that large parts of the upland were used as turbaries by the commoners who owned the farms and smallholdings on the flanks of the mountain.

Dolerite boulders litter the surface near Carn Sian, with Carn Bica in the distance



Cerrig Marchogion

Grid ref SN 112 323.  Alt. .  Here, on the crest of the upland ridge at an altitude of about 400m, the strange craggy outcrops of Cerrig Marchogion make a lasting impression on all who pass by on the nearby Golden Road. They are really small tors and rock outcrops made of dolerite, surrounded by a litter of broken boulders affected by frost action and moverd about by glacier ice. There is a magical quality about this place, especially when it is raining, or when low cloud or mist is drifting across the mountain ridge. Literally, the name means "the stones of the knights". The explanation for the name can be found in the ancient book called "The Mabinogion", in the story of Culhwch and Olwen. This is adjacent to Cwm Cerwyn where, according to legend, King Arthur and his knights fought a pitched battle with the wicked black boar Twrch Trwyth and his cohorts. So bloody was the battle that eight of Arthur's knights were killed, and the rocks are supposed to be their petrified remains.

One of the little crags at Cerrig Marchogion

Cerrig Marchogion.


One of the "mini tors" at Cerrig Marchogion

Craig Talfynydd

Grid ref SN 130 314.  Alt.  .  This is a series of rock outcrops with banks of scree and broken slabs on the eastern flank of the Talfynydd spur. Literally, the name means "crag on the end of the mountain".  This is a beautiful sheltered spot when the wind is in the west or north-west, with many gullies, dolerite outcrops and grassy banks to explore. Some small trees have managed to survive in the rocky wilderness. Because the slope is quite steep in places, some of the rock slabs and scree banks are still moving periodically but inexorably downslope; they are therefore quite unstable, and great care is needed when you clamber across them. There is a very large rabbit warren here, and you are certain to see rabbits of all ages scuttling about among the rocks. The spring below the crags is used to supply water to the cottage of Dan-y-garn in the copse of trees.

Craig Talfynydd

Craig y Cwm

Grid Ref. SN 096 313.  Alt.   .  This rocky outcrop high above the hollow of Cwm Cerwyn is not really a tor, but a series of crags and cliffs created by a combination of glacial action and frost shattering. The name means "the rock of the valley". Located quite close to the Presely summit of Foelcwmcerwyn, the altitude here is about 490m. The crags are made of slates and other rocks metamorphosed close to the dolerite intrusion which outcrops on the mountain summit. Down below there is a small and very old slate quarry with pits, cuttings, a trial tunnel, spoil heaps and a cart track running southwards around the end of the spur. The quarry excavations have made Craig y Cwm quite dangerous, especially when the grassy slopes are wet or when visibility is bad; this is one of the few places on Presely where a serious accident can happen if you are lost in the mist. A few years ago there was a fatal air crash here when a light aircraft en route from Swansea to Dublin flew into the side of the mountain in poor visibility.  The cwm was probably the site of the last small glacier in Pembrokeshire;  morainic traces and exposures in stream cuttings suggest that there was a small glacier here around 10,500 years ago.

Craig y Cwm and the quarrying trackway

Foel Drygarn

Grid Ref SN 158 336.  Alt. . This prominent hill mass towards the eastern end of the Preseli upland ridge stands in glorious isolation, and the summit can only be reached via a stiff climb from the nearly "Golden Road" footpath.  It is such a sizeable hill that, like Carningli, it should probably be referred to as a "derelict volcano" -- but we have to include it in our list.  The name means "the bare hill with three cairns" -- and the three massive Bronze Age burial mounds on the summit are the most spectacular features of this age in Pembrokeshire.  They lie within the confines of an Iron Age hillfort which contained both an animal enclosure and a substantial settlement site.  Scores of hut circles can still be made out in the turf.  The defensive ramparts are prominent.  A gorgeous location, with spectacular views in all directions.  There are tor-like spectacular crags towards the western end of the summit.  Beneath these crags there are clear traces of prehistoric quarrying activity -- this is where the slabs of rock used in the burial cairns and the embankments have come from.  The rocks are rhyolites rather than spotted dolerites, and as with the other high tors the dominant process which has shaped the crags in recent millennia is frost shattering and the downslope movement of detached blocks under the influence of gravity.  The jury is still out on whether the summit of Foel Drygarn was affected by glacier ice during the last glaciation.

The crag above the old (probably Bronze Age) quarry at Foel Drygarn.  The three burial cairns are made of locally-sourced slabs and blocks of baked shale and volcanic rock.

The three summit cairns and the defensive fortifications on the summit of Foel Frygarn.

One of the crags on the south side of the Foel Drygarn summit, with a destroyed semi-circular embankment made of large boulders.

Ice-smoothed slabs on the summit of Foel Drygarn.


Carnau Ysfa

Grid Ref SN 083326.  Alt. .  A small tumbledown tor near the western end of the Preseli ridge, on the north flank of the mountain, looking down on Banc Llwydlos.  It's quite close to Carn Fach, and is within easy walking distance of the parking area on Bwlch Gwynt.  Actually there are a series of small outcrops scattered across the grassy landscape -- none of them particularly prominent.

One of the small outcrops of Carnau Ysfa.  In the distance, Foel Drygarn and Frenni Fawr.