A GEOLOGICAL RUN OVER & AROUND CARROCK FELL by Richard Clarke
The route map can be found on the OS Maps website or app (titled: Northern Fells RC: Geology Run Over Carrock Fell), here.
Run distance: Approx. 9.43 miles
Total ascent: 3,013 ft
Start / Finish / Parking: Calebreck. N.G.R. NY 345 358
Abbreviations: “my”: million years
Small print: Northern Fells RC accepts no responsibility for your safety in attempting this route. It goes high and fairly long across open mountainside as well as down steep rocky gullies. In the Northern Fells there are fenced areas to keep people & animals safe from old mine workings: do not cross these fences, some of the shafts are 300ft deep. Do not enter any of the cuts into the mountainsides either; instead pack your head torch and peer in safely from outside. Finally, all NGR’s are approximate using the OS Maps website.
There are 16 stops in total and the route / what to see at each stop are described below:
- STOP 1: START: Calebreck Car Park. NGR: NY 34587 35837
Ahead of you is Carrock Fell, one of the key peaks of the Northern Fells. The Northern Fells or “Caldbeck Fells” are a geologically unique area in terms of the rest of the national park and the UK. Beyond Carrock, at Skiddaw and the rest of the Northern Lake District, the rocks are predominantly either Borrowdale Volcanic Group (BVG) or Skiddaw Slate Group (SKG).
As an introduction to Lakeland rocks, the SKG are very old rocks, 500my (Ordovician period), formed from sediment in a shallow seabed off the continental shelf some 500-480my ago. They represent some 20my accumulation of sediment that has subsequently undergone intense compression and metamorphism (this is the transformation of rock by heat and pressure). The SKG is approximately 5000m thick in bands of sandstone, siltstone and mudstone. As the SKG is so old, it’s been subject to tremendous folding and faulting and slumping – you’ll see amazing evidence of this (one of the highlights of the tour) at Stop 10 on the other side of Carrock Fell on the banks of Carrock Beck.
Volcanic rocks overlie the SKG: the BVG and Eycott Volcanic Group (EVG). These rocks were formed some 400-450my ago. A period comprising an estimated 10my of volcanic eruptions, resulting in the deposition of several thousand meters of lava.
It’s not entirely clear what occurred to these Lakeland rocks between the volcanic periods of 400my ago, the sedimentary period of 500my ago and the last ice age of 2.5my ago. It is thought the rocks could have been covered in chalk deposits, however, mountain movement (significant orogeny events some 66-23my ago) would see this chalk layer uplifted, folded, and broken and removed. Orogeny is the main means of mountain building and occurs when continental plates crumple in contact with another and are pushed upwards to form mountain ranges. It is thought the Lake District mountains would at one time, as a result of this orogeny, been comparable in size to the Alps today, but today what we see are the eroded remains of those.
In terms of right now (today), the Lake District landscape you see ahead of you is a result of geological processes over the last 60 my, with the biggest influence on the landscape occurring in the last 2.5 my and the last period of glaciation, approximately 20-10,000yrs ago.
Glaciation eroded the land surface and created the U shaped valleys, including that which we’ll see later from Lingy Hut (Stop 12). Once the ice melted, the water and the material from glacial erosion would form soils covering areas of rock (our predominantly grassy Northern Fells that we see today).
As you head off to Stop 2, looking down the road towards Mungrisedale (SE direction), you’ll get a good view of the Mosedale Valley. This flat area at the base of Carrock Fell was once a glacial lake.
From Calebreck, head SE, down the rd. towards the ford. Cross the ford (there’s a pedestrian bridge if you prefer) and continue down the right hand side of the rd. At NGR NY 350 348 you will see a small trod leading gently up towards the NE base of Carrock Fell.
- STOP 2: Carrock End Mines incl. “Queen Mine”, NGR: NY 351 342
This mine is very old and at this spot you can see a drive into Carrock Fell, with water gushing out of the entrance (Don’t enter for your own safety). Tyler reports Queen Mine was definitely being worked in 1570. The Northern Fells are regarded as the jewel in the crown in terms of Lakeland mineral and mining. They became synonymous across the UK with prosperity and led to the famous saying “Caldbeck and Caldbeck Fells are worth all England else”.
Carrock End Mine and later mines extend along the road here and we’ll run along them before beginning the climb up Carrock Fell via Rake Trod. They are the most easterly of the Caldbeck Mines and were last worked c.120yrs ago.
Principal deposits were Copper and Lead. Tyler points out that there was a 40ft water wheel installed here from the mid 1800’s for the pumping of water from the mine and if you look closely in one of the rocky clearances you can see a horse whim – a clear hole cut in the centre of a stone lying flat on the ground within a small clearing. This would have been the location of a wooden pole to which a horse would have been attached to drive machinery.
If you look up at Carrock Fell from here you’ll see gullies coming down the fellside towards you – these are “flushings”, man-made cuts to direct water and expose mineral veins. Later, we’ll also see “leats” (Stop 13), these are similar narrow gulley features but fall at a gentle angle across the fellside i.e. cut at just the right angle to give just enough in the fall of the water to power the water wheels of the mines. Don’t return to the road; continue at this height along the base of Carrock Fell, passing in between the mounds and rocks of the former mining activity.
- STOP 3: Base of the track to Carrock Fell summit (Rake Trod), NGR: NY 353 338
Before climbing, notice that the line of the road ahead (down the valley towards the S: towards the A66) follows the “Carrock End Fault”. As you climb upwards notice how the colours of the rocks below your feet will change: the grey crystalline rocks at the bottom of the track (rough blocks and large boulders) will become darker as you gain height. These are the darker “Gabbro” rocks of Carrock Fell. You might be familiar with Gabbro rocks from the Cullin Ridge on Skye for example. Gabbro is an igneous (i.e. volcanic) rock, rich in iron and magnesium minerals. The Gabbro rocks are not formed by surface volcanic activity but instead they were solidified at depth as hot magma intruded into the SKG unit. Consequently, the rocks exposed today on Carrock Fell were once buried in the earth’s crust, coming to the surface as a result of plate tectonic activity. We’ll see evidence of the immense movements these rocks have been subjected to at STOP 10 in Carrock Beck later. Note that the magma intrusion would have “baked” surrounding rocks. This led to the mineralisation of the rocks and that led to the mining opportunities. Then, near the summit of Carrock Fell, as you reach the area indicated on maps as the “Scurth” (a landslip feature), you should notice beneath your feet the presence of pink and grey granite rocks. This is Granophyre. It is tough and hard and weathers to form small pieces of rock and some fine sand (you might notice this most during the drier summer months when parts of the trod to the summit can appear quite sandy).
- STOP 4: Before beginning the steepest part of the ascent of Rake Trod, pause to look across the valley below you NGR: NY 351 333
An excuse for a breather!
You get good views here down the Mosedale Valley to the S and E. Take a moment to look down below you into the valley bottom. You can see some fields, but also marshy areas. The rocks underlying the valley, as a result of the Carrock End Fault comprise SKG slates overlain by boulder clays. The latter were deposited during the last ice age, when the flattish area across the valley bottom would have been a large glacial lake. If you look across the valley towards the SE, you can see some small hills – these are the Eycott Hill exposures (part of the BVS) and are remnants of ancient lava flows. If you look straight across the valley you can see Greystoke Forest. This location sits on top of Carboniferous Limestone (350my). You’re looking forward in geological time here: the igneous BVS (Eycott Hill) rocks are overlain by carboniferous limestone, which if you imagine travelling further east towards Penrith are then overlain by younger still Triassic Sandstone (think about the red sandstone used in buildings in Penrith). On the horizon to the SE you can see Little and Great Mell Fell. These are sedimentary conglomerate rocks, hence their rounded shape. Beyond the two mell fell’s on the horizon is High Street (BVS rocks).
- STOP 5: Carrock Fell summit approach (Hill Fort), NGR: NY 344 336
You’ll pass through the remains of the wall around an ancient enclosure constructed between -2600 to -700 yrs.) of either Neolithic or Bronze Age origin. The Historic England reference can be found here. It also features in a Dickens story (Dickens is known to have visited Ireby and the Northern Fells in the 1850’s) and has been described as the largest known hill fort in Cumbria (here). This eastern end of Carrock Fell is classified as a Geological Conservation Review Site. The fell is internationally significant in terms of its example of crystallization in layered igneous rocks. From the summit cairn we’ll head E across the spine of Carrock Fell, heading for the top of Brandy Gill (Stop 7)
- STOP 6: East off the summit of Carrock Fell, NGR: NY 333 338
Now as you run E across Carrock Fell notice that the rocks will change and you can spot within the main trods a grey/green greisen rock: this is Greisenised Granite. Greisen is an intrusive (metamorphosed) igneous granitic rock. It is composed mostly of light-colored mica and quartz. Granite is composed of crystals large enough to be seen because the magma forming it has cooled and solidified slowly at depth, giving individual crystals time to grow. The granite has metamorphosed itself to greisen via hot magmatic fluids that contained many chemical elements incompatible to the common minerals, so forming granitic intrusions. This is the reason why greisen is usually a natural concentrate of somewhat unusual minerals. Some of them may be economically interesting – hence the local mining activity. The mineralisation occurs as a result of a process called pneumatolysis: in granite rocks like those at Carrock Fell, during their formation the highly actives gases and fluids associated with the magma are driven off and attack the rock itself, breaking down the constituent minerals present (typically feldspars) and replacing them with others. For example: tungsten is deposited around temperatures of 170-350 0c, lead at temperatures less than 170 0c. The term “greisen” was originally a german mining term, like the word Gneiss (a slightly different type of metamorphosed rock to greisen).
- STOP 7: Farm-gate entrance to the top of Brandy Gill, NGR: NY 3221 3407
The mines of Brandy Gill are reputed to be one of the most interesting old mine locations in the Northern Fells, due to the richness and variety of minerals present.
Note that it might be hard to see very interesting minerals on the surface: these areas and their spoil heaps have been worked over by locals, visitors, mineral collectors and the like for over a hundred years. Now you’ll need a permit – see here. But, if you look closely and dig a little into a heap with your foot you are likely to find traces of wolfram (principally Manganese & Iron): it’ll appear black and shiny, often visible as a blade-like form within quartz in the rock. The pinkish brown spoil heaps towards the top of Brandy Gill are evidence of Calcite. Also, look out for scheelite (a yellow / brown resin, which has a lilac fluorescence under UV light). Pale greens indicate Apatite. Vivid green and also a tarnished yellow/brown colour can be traces of arsenic. Gold is also reputed to have ben found within Brandy Gill and on the Harding lode (Stop 9). If the ghyll itself is not in spate, look in the channel for trial holes left by historic prospectors, as well as traces of mineral veins visible in the rocks in the streambed.
- STOP 8: Waterfall & Brandy Gill Copper Mine, NGR: NY 322 337
Tyler notes that this was worked for lead and copper in the early eighteenth century, with at least 3 productive levels, closing circa 1860. In the beck below the mine, beside the waterfall, is a large mine opening into the fellside (an open trial). Head torches out and peer inside from the safety of outside.
- STOP 9: Carrock Wolfram Mine, NGR: NY 323 329
Hard to believe, but this was last worked in 1981, with substantial earth movements in the name of landscaping having taken place since then (a great shame in some ways). Wolfram (and Scheelite) is an ore of tungsten and was not worked commercially anywhere else in the UK. Indeed, it is the only mine of tungsten ore outside the SW of England. The wolfram and scheelite veins here were 2-4 ft thick and the mine workings extended 800 yds. into Carrock Fell by 1972.
Sorry, but you now head off to the SE down the road towards Mungrisedale (i.e. losing height and having to come back on yourself)…however, Stop 10 is worth it!
- STOP 10: River Caldew excursion, NGR: NY 330 326
On the roadside, looking towards the River, look closely at the rock outcrops below your feet– the incredibly wavy lines you can see represent the folding and faulting of these Skiddaw Slate beds over millions of years of movement in the earths crust – have to be seen to be believed (!). Now head back up the road and up the path towards Lingy Hut – you have to run back up the road, but at the junction with the old mine track its possible to take a lower trod and run nearer the beck below. Take a moment to look at the information board, which highlights the mineral veins and has some great old photos of what the place used to look like, thanks to Cumbria Amenity Trust Mining History Society (CATMHS) – a society interested in historical industrial sites with an emphasis on mining. You can also see a restored mine entrance just below the information board. But this is a run, so get going and as you climb up to the hut you’ll see the same transformation in rock appearance that we saw on the climb up Carrock Fell via Rake Trod: as you gain elevation the rocks will become darker gabbro’s, granophyre then nearer the hut, greisen’s. Also nearer the hut you’ll step in peat deposits. This has been formed in the early post-glacial period (within the last 5000 yrs.), facilitated by post-glacial depressions and the moist Atlantic climate prevailent over this period.
- STOP 11: Lingy Hut NGR: NY 312 336
A beautiful facility, thanks to the Mountain Bothies Association (please treat it with respect): turn around and look down the valley, it’s a great view and Lingy Hut now has a window to admire it. If you look at the valley sides, around the 200 m contour level you can see a change in slope angle – the gentler slopes of Carrock Fell to the left would have formed the pre-glacial valley. Post glaciation the valley has been cut deeper. Now head NE on the main path towards High Pike. You can go up High Pike if you want, but otherwise turn right off this main path and drop into a branch of Dryghyll at Stop 13:
- STOP 12: Turn right and go down into Dryghyll, NGR: NY 318 346
Dryghyll Shales are exposed here; the grey shales are particularly exposed on the left of Dryghyll as you had down into it. On their discovery by geologists Nicholson & Marr in a paper published in 1887, they are recorded as being found “in a dreary valley, sometime dry, appropriately called Dryghyll, near the top of a col between Carrock Fell and Great Lingy”. There’s nothing dreary about Dryghyll for 3 principal reasons: 1) you get a real sense of isolation, especially on a cloudy day, but more importantly, 2) it’s a world famous site for campylite (green barrel shaped crystals, mainly lead based) – the only location in the UK where this mineral can be found! and 3) the Dryghyll shales are unique to the rocks we’ve looked at previously as they’re much younger than the rocks around them – yet they’ve managed to “survive” (elsewhere the younger rocks have been eroded by the actions of time, earth movements and more recently glaciation). Marr described the shales as “very queer” and nothing like anything he had seen previously in the Lake District. The shales are still old (Ordovician period: 450-500 my), but uniquely examples of fossilised Trilobites have been discovered in these shales in Dryghyll. The Ordovician period is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates). Nearly all life on earth at this time was in the oceans. The only land life was in the form of very primitive plants very near the water line of the coasts, probably mosses and algae. However, all this would end with the so-called “end-Ordovician extinction”: the second largest mass extinction of all time, when around 443 my ago, 85% of all species on Earth went extinct. The extinction was most likely as a result of the principal landmass of the time, Gondwana finally settling in an area that is today the South Pole. Consequently, massive glaciers formed and there was global cooling: shallow seas drained and there were reduced, cooler sea levels, which dramatically impacted the many marine species living in warm, shallow coastal waters. If you have a root around here, you can spot copper (bright blue and green tarnishing features on the rock – that brilliant verdigris colour). Just to prove there are fossils, local Julia Garner found a fossil here in 2015: you can see a photo on her blog here
As you get to the end of the steep sided Dryghyll, look up to the clear outcrop of a different rock – this is a fault boundary between the shales and the lavas of the BVS.
- STOP 13: At NGR: NY 324 345 cross flank of High Pike, heading to Driggeth Mine
Where you emerge from the steep sided upper section of Dryghyll, traverse the Eastern flank of High Pike and head across the flank to Driggeth Mine, its scar is visible clearly to the NE. Be careful not to lose too much height as there is plenty to see at Driggeth – it’s a great run across. As you emerge from Dryghyll look behind you to the flank of Carrock Fell and the grassy lines clearly visible above you are former mining “leats” as described in Stop 2.
- STOP 14: Driggeth Mine Terraces & Offices, NGR: NY 329 350
As you run across from Dryghyll aim for the concrete terraces towards the bottom of the mining area at the approx. NGR above. These are remnants from the 1940s operations: office foundations and old jigs lie around. Its been a mine since the sixteenth century and in its later years its workings became the high levels for the “Sandbeds Mine” the remnants of which are still so visible on the other side of High Pike at NGR NY 331 360. Driggeth was valuable for lead and copper. In 1800 it produced 200 tonnes of lead pr yr, employing some 30-40 miners. The lead contained a lot of silver, although much of this was burnt off during the smelting process – nevertheless, Driggeth produced approximately 1 tonne of silver during its operations. Look up (to the N-NW) and you see a large scar on the landscape around the Driggeth Mine. Mining began here using the process of strip mining: water was collected up the valley and it washed down to expose the mineral rich veins situated at shallow depth here. Later, cuts into the mountainside were used. Above us there is an open level (not included on this run, but one for a future route) – Pattinsons Level. This is still open, but do not enter: the openings associated with Driggeth are notorious for collapses and old timbers have been known to give way in front of mineral hunters. Pattinson after the “Pattinson Process”: Hugh Lee Pattinson discovered, in 1829, that the crystals formed during the slow cooling of molten lead were poorer, and the remaining liquid richer in silver, than the original lead. This was the first process applicable to the de-silverisation of low-grade lead bullion, saving many ounces of silver annually, which previously had been thrown away. The process was expensive compared to modern methods; labour intensive too, with the resulting silver tonnage small, but the results were satisfactory.
Now head E down the valley via the main path. Where this splits at NY 341 351, head off the main track to take the path to the left and curve around the small rise to head for the Howthwaite Stone, giving good views back to the car at Calebreck.
- STOP 15: Ancient Smelter & View of Rospow Hills, NGR: NY 344 354
Pause a moment here and look back towards Carrock Fell, but not to the summit, rather the land just above the Rospow Hills, small, likely glacially derived hills on the opposite bank of the beck. On the lower slopes of Carrock, almost opposite you can see a large square stone sheepfold, the area of land to the left of this is an Ancient Monument. Archaeological surveys during the 1980’s-90’s concluded that the small bumps and hollows visible if you look closely are earthworks and the buried remains of a Bronze Age (prehistoric) farming landscape comprising around 20 circular and oval shaped clearance cairns up to 0.4m high, with the fields comprising 9 short lengths between the stone banks.
Now continue on, heading towards Howthwaite Stone. Before reaching the stone you will come across paths and random stones coming together from the flank of West Fell of High Pike, in the centre of these is a small patch of blackened stones, with limited vegetation. This is “Howthwaite Smelter”: discovered by Ian Tyler and Dave Blundell around 1983. Tyler describes it as an ancient (medieval) smelt site and if you look closely at the black rocks you will find traces of charcoal and slag. The charcoal here has been carbon dated to 1020-1200 AD! Slag is the by-product left over after a desired metal has been separated (i.e. smelted) from its raw ore. During smelting, when the ore is exposed to high temperatures, impurities (oxidized materials, silicates of other metals) are separated from the molten metal and removed. Slag is that collection of compounds that are removed.
- STOP 16: Howthwaite Stone, NGR NY 343 355
Likely left here by glacial action. It could be described as a “glacial erratic”, erratic in the sense that glacial action has transported and deposited a rock much larger than those in the immediate vicinity.
- STOP 17: Calebreck Car Park: FINISH.
Thanks for providing a lot of the mining and historical information in this route must go to the books of Mr Ian Tyler, who has written about mining history all across Cumbria & Westmorland. He and others have done incredible work over many years