The Lake District, Cumbria.

Firstly a quick note. The Lake District is famed for its geology and mineralogy and now in the spirit of preserving it for all by not allowing anyone near it these resources are now managed by the Lake District Park Authority. This means that hammers and mineral collecting are banned or severely restricted in many areas. To find out where these restricts apply, contact the LAPD, Murley Moss, Oxenholme Road, Kendal, Cumbria LA9 7RL Tel: 01539 724555 Fax: 01539 740822.

The Lake district can be divided at a very simple level into 2 zones. The southern half below an east-west line drawn on the map through Keswick is predominantly of volcanic origin, whereas the northern section is sedimentary.

Great Langdale.

We began our stay at the Great Langdale National Trust Campsite (NY286058). This campsite is located at the head of this obviously glacial valley: U shaped, between high jagged cliffs of hard volcanic rocks, ending in a steep dead end.

A little way down the road from the camp above the New Dungeon Ghyll Hotel (NY295064) a hanging valley cuts the side of the main valley. A well laid path follows the beck from the car park behind the hotel, climbing steeply up past a series of waterfalls. Dungeon Ghyll Force: The largest of these falls, drops for about 10 metres over a cliff of very hard, fine grained rock with a slight red tint which may be an igneous intrusion into otherwise fine gritty greenish rocks of andesitic origin.

The path reaches the head of the valley quite suddenly opening onto Stickle tarn, a large lake backed by a semicircle of steep cliffs formed by the head of the glacier. Following the path to the left (west) as it continues up and around the back of this glacial corrie, the first thing that strikes you is a sudden change in the nature of the rocks. A little above the tarn the fine grained ash layers are suddenly replaced by a coarse agglomerate containing angular fragments up to the size of a football in a gritty matrix. This persists right to the top of the hill where it is overlain with a rapidly eroding cover of dark peat.

Stickle Tarn

The path down follows a straight course in what appears to be a shallow valley between walls of the agglomerate rocks. Inspection of the rocks underfoot reveals them to be dark, fine grained and apparently in many layers stood vertically. This is possibly a basalt dyke intruded into the agglomerate possibly in a series of events giving the layered appearance. The layering has been its undoing as it has weathered and broken up much faster than the unbedded surrounding rocks to form this little valley. The path returns to the head of the hanging valley. From this vantage point the glacial nature of the main Great Langdale valley can be best appreciated. To the west is the head of the valley, to the east the sides become lower, the valley widens and finally opens onto the head of Lake Windermere at Ambleside.

Dyke cutting the volcanic conglomerate.

Returning to the Dungeon Ghyll Hotel, if you take the road towards Ambleside you will see some other glacial features. In a number of places beside the road excavations have been made for houses etc. and in most of these banks thick boulder clay is exposed. A little further on at Elterwater, the valley is now wider and glaciers have deposited extensive moraines. These form natural dams for the small river thus forming a series of shallow lakes.

At Skelwith Bridge where the road joins the main road to Ambleside there is a slate works (NY342034). This was once tied in to the slate mines in the valley but now imports stone from Lakeland and beyond. The 2 owners are both very approachable and are happy to talk about the works. At the far end of the yard beside the public footpath is a block of slate about 5 feet high and 6 across with a 3 foot long engraving of a Coelacanth. A little beyond the road junction towards Ambleside a series of wooded drumlins can be seen on the shallow valley floor, though they are a little obscured by trees.

Wrynose Pass

This pass can be reached by taking the small road which leads up over the head of Great Langdale. The head of the pass (NY276026) is at an elevation of almost 400m and gives a great view of a glacial valley in either direction. However, looking east, the ground drops steeply at first then opening into a wide valley the floor of which is extensively humped with kettle moraines. These can be seen in many of the valleys but this was one of the clearest views we came across. To the west the road drops in hairpin bends through Hardnott Pass to the coastal plain. But at the bottom of the descent keep half an eye on the walls at the roadside. The stones from which they are built change suddenly from grey/green fine grained ashes to granite and back again a mile or so either side of the village of Boot. This granite however is very soft and the blocks in the walls have a rounded appearance (unlike the sharp walls seen on Dartmoor for example).

Kettle morraine

Honnister Slate Quarry.

The drive rom Keswick through Borrowdale to Honnister is worth the time in itself. This is another U shaped glacial valley only here it has been cut almost on the junction of the volcanic-sedimentary transition, leaving steep heavily wooded valley sides to the south and more rounded to the north. The road climbs steeply up the head of the valley above Seatoller and opens onto the bleak Honnister Pass.

The slate quarry is situated at the very head of the pass (NY224135). Re-opened in the mid 1990s there are frequent (though not cheap) tours underground. The tour takes you into the side of the mountain along a narrow passage built up of 'deads'; the blocks of stone of no value to the old miners. This opens out into 'Fiddlers Chamber' where a great deal of stone extraction has taken place.

The valuable slate from the mine occurs in 3 levels and has been formed from fine-grained green volcanic ash, which is for the most part free of coarser rock particles or iron pyrite crystals. Fiddlers Chamber has exploited one of these levels where it dips at about 40 degrees but here a lava sill roofs the slate layer. The miners initially exploited the stone from lower down and have been steadily tunneling up inside the mountain.

The tour guide will tell you that this is far better slate than the Welsh slates, that it will last 300 years and is to be found on the roof of Buckingham Palace. She will take it quite well though if you tell her that the slates from Roseland quarry in Pembrokeshire are used on the houses of Parliament.

Ullswater.

Ullswater lies in the east of the Lake District. The rocks on the northern side of the lake are sedimentary in origin and date to the Ordovician and Silurian and here the hills are rounded and the lake beaches are of grey pebbles. The rocks of the southeastern side are volcanic tuffs, harder, dropping steeply down to the water with only very small beaches backed by sharp high hills. A line drawn from the southern tip of Ullswater, west past Derwent Water marks the continuation of this north-south divide in rock types; to the north the Skiddaw Slates, to the south the Borrowdale Volcanic Series.

However, a short time sat on any of the beaches will show glaciers have been at work. In many places banks of boulder clay are exposed at the back of the beaches and a search of the beach stones will yield varieties of the local stone but also granite, basalt, diorite, all 'erratics' brought in by glaciers.

Greenside mine (NY362175) occupies the head of the valley above the village of Glenridding. Many of the mine buildings have been preserved as a youth hostel, bothey and private houses. Once these were the dries, mine captain's house, smithy and other buildings serving the mine. The local workforce was supplemented by slate workers from Keswick who climbed the Sticks Pass over the shoulder of Helvellyn looking for work.

The principle output from the mine was the lead ore galena and this can be found abundantly on the tips. The ore appears to have been emplaced directly as stringers into fissures in the slates often without any associated mineralization. This differs from mineralization in Devon and Cornwall where galena normally occurs associated with calcite or fluorite. However, in the Lake District fluorite is uncommon, though at Greenside calcite, barite, sphalerite and quartz, all common lead associates in hydrothermal deposits, are also found. The works along the course of the valley are impressive in their scale but it is only once you reach the topps that the true scale can be fully appreciated. The valley floor is crossed by long tongues of rubble, the valley sides are cut by several open cast pits and the ground is hummocked not with kettle moraines but by grassed over tips. Here too there is evidence that there were once mine buildings: a large expanse of sand shows the location of the stamps and there is the foundation of a single building with the end of a flat rod assembly next to it.

Baryte

The Scottish Southern Uplands.

On our northward journey we struck off from the M6 motorway at Moffat and headed eastward taking the A701 into Edinburgh. This passes up over the rolling Southern Highlands, circumvents the Devil's Beeftub, deriving it's name in no small part from the outcrops of Permian red sandstones and the source of the river Tweed and approaches Edinburgh along the line of the Pentland Hills.

On our return south we left the M6 at Abington heading southwestward towards Wanlockhead. This is an area shaped by the action of an ice sheet on underlying Permian red sandstones. Surprisingly much of this range of rolling hills has a greater elevation than the more mountainous Lake District. The reason for this is that these are fairly soft and thinly bedded rocks; without hard igneous intrusions and were thus worn into curves rather than sharp peaks.

It also contains another major lead mining centre: The Leadhills. We checked over the roadside tips of one mine just outside the village of Leadhills itself and found plenty of Galena, but also some lead secondary minerals: pyromorphite, cerussite and brochantite, as well as pyrite, barite, chalcopyrite and malachite and hematite.



Edinburgh

Arthur's Seat, Sailsbury Crags & The Dynamic Earth Exhibition.

This is well worth making a day over. In hindsight my suggestion would be to park in the underground car park at Dynamic Earth, at the End of the Royal Mile, next to the Scottish Parliament. From here it is a short step across the road to begin your exploration of Arthur's Seat.

A steep path ascends the slope below the cliff face of Sailsbury Crag. This contains the output of at least 13 lava flows, some of which may have been laid down in a shallow carboniferous sea. Walking along the path it is easy to pick up a variety of igneous rocks from dark very fine grained basalt through to those with dark matrix and white feldspars.

Limestones in lava flows

There are also patches of highly weathered limestones and mudstones, mostly with a dark pink colour. One section of this is highly contorted into an S shape with 2 opposing 90 degree bends in under 2metres. As the volcanic beds of the crag show very little folding I suggest that this piece of mudstone is a xenolith carried to its present location by the lava flow. At the end of Sailsbury Crag a short clearly glacial valley separates the crag from the main mound of Arthur's Seat. Here also is an exposure of rock with many small holes in the surface. These are the product of weathering out of one of the components, as a freshly broken surface shows none of these holes.

There are several routes from here to the top of Arthur's Seat but take the route that leads diagonally off to the left. This circles the eastern shoulder of the hill to join the main pathway to the top and is a fairly gentle approach. Towards the summit the path is marked by a series of iron posts linked with a chain. At this point the rock surface is clear of grass in big patches and somewhat resembles pillow lavas. Whitlow in his book 'The Geology & Scenery in Scotland' refers to some evidence of underwater eruptions without saying pillow lava but this may be what was being referred to.

From the summit there is a fine 360-degree view but look back to Edinburgh to get an excellent view of 'crag and tail' scenery. At the time of the last glaciation the ice sheets moved west to east (left to right as you look over the city). Where the ice met hard volcanic rocks it ground away the softer rocks in front of these obstructions and was deflected around the sides producing the high crags seen at Edinburgh Castle and Carlton Hill. With the ice deflected by the crags the softer rocks behind were protected and remained in place, for some time it was thought that these tails were deposited from the ice but it accepted that these are in fact the original rocks.

The other effect of the deflection of the ice was that there was more erosion between the crag and tails, which produced over-deepened valleys such as Waverley Gorge where the railway station is sited.

The Dynamic Earth Exhibition is situated in the building at the foot of Sailsbury Crags beside the new Scottish Parliament. The first section takes a quick journey through the first 13 billion years of the Universe's lifespan, dropping you off at the beginning of an interactive exhibition from Cambrian to modern times. If you've studied S193 'Fossils & the History of Life' play your own game of identify the replica. But by far the largest section depicts ecosystems of modern Earth and features an iceberg in the arctic room. Well worth it.



Edinburgh Castle.

Less of the castle and more of the rock on which it sits. A large volcanic vent filled with very fined grained black basalt and now largely exposed on 3 sides and in places above where it has not had castle built on it. Take the footpath around the North side. Do not take the footbridge over the railway but carry on towards a gate into a gravel car park. In several places along this section horizontal grooves can be seen in the rock of the castle mound, cut by rock fragments embedded in the moving glacial ice. If you fancy a souvenir of Edinburgh then this is the place to collect a small fragment of the castle rock as it seems there must be a steady rain of pieces off the mound and onto the footpath.

Glacial grooving. (yeah baby!)

It is also almost possible to see the junction of the basalt and country rock but to do this you have to pay your entrance fee to the castle. The road inside the main castle gate heads up to the right passes the gift shop and then enters through the portcullis gate. But if you keep an eye on the rock exposures to your left there is a change from the highly fractured dark grey rocks: the metamorphosed carboniferous country rock, to the less fractured, almost black basalt. However, in an act of geovandalism, the actual contact has been covered over with an 18-inch wide band of concrete. I can only assume that this is because the contact represents a line of weakness and had been weathering away.

Useful references:

British Geological survey 1:625000 north sheet (obviously).

J.B. Witlow, 'Geology and Scenery in Scotland', Penguin Books, 1979.

A.E. Trueman, 'Geology and Scenery in England & Wales', Penguin Books, 1977.

E.H. Shackleton, 'Lakeland Geology', Dalesman Books, 1991.

Click here for extra photos.

Words & photos: C. Popham

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