Geology of Cumbria

An Overview

For its size, Cumbria is one of the most geologically diverse areas in Europe, including as it does, an exceptionally wide range of rock types and landforms.

In broad terms, as can be seen from the geological map (Figure 1), the central part of the county is occupied by a roughly circular inlier of Ordovician and Silurian marine metasediments, volcanic and volcaniclastic rocks, and granites. Together these form the rugged landscapes of the Lake District National Park, the boundary of which roughly follows the borders of the inlier.

Surrounding the Lower Palaeozoic inlier are the Carboniferous limestones and sandstones of the Pennines, West Cumbria and South Cumbria, and the Permo-Triassic sediments (mainly red sandstones and mudstones) of West Cumbria, Carlisle and the Eden Valley.

Figure 1 Geological map of Cumbria (Image courtesy Yorkshire Geological Society)

All these rocks have been subjected to tectonic disturbance to varying degrees over the region’s 480-million-year history. Uplift, folding and faulting, have imposed structural controls on landscape development, influencing large-scale drainage patterns, the distribution of river valleys and lakes, as well as the boundaries of the Pennine and Lake District uplands.

The contrasting landscape character of the different parts of county owes a great deal to the underlying rock-types. The rugged mountainous scenery of the Lake District is formed from erosion-resistant granites, metamorphosed sediments and volcanic rocks (Figure 2). Outside this core of older rocks, Carboniferous limestones form a belt of hill country on the southern, eastern and northern edges of the Lake District (Figure 3) as well as the high moorland plateaus of the Pennines in the east.

Figure 2  Lower Palaeozoic metasediments, granites, and volcanic rocks produce the mountainous landscape of the Lake District fells. Here looking northwards from Great End towards Great Gable (middle distance) composed of Ordovician (Caradoc) volcanics rocks of the Borrowdale Volcanic Group. On the distant horizon are the outlines of Skiddaw (right) and the Lorton Fells (centre) composed of older Ordovican (Tremadoc – Llanvirn) marine mudstones and sandstones known as the Skiddaw Group. (Photo: Stuart Holmes)
Figure 3 At Moota, near Cockermouth, Carboniferous Limestone (foreground) forms a series of low hills around the eastern margin of the Lower Palaeozoic inlier seen in the distance. Skiddaw dominates the skyline. (Photo: Ian Francis)

Succeeding these rocks in the stratigraphic succession are red Permo-Triassic sandstones which – as well underlying the low pasturelands of the northern Cumbrian plain, West Cumbria, and the Eden Valley –   produce the dramatic coastal scenery around St Bees and Whitehaven.

Figure 4 Red Triassic sandstones (St Bees Sandstone) forms the cliffs on the St Bees Heritage Coast south of Whitehaven.  The Isle of Man can be seen on the horizon. (Photo: Stuart Homes)

The different rocks have weathered to give diverse soil types (which in turn affect natural ecosystems, as well as agriculture). The region’s rich mineral resources, such as roofing slates, building stones, metal ores, and coal, have strongly influenced local settlement patterns and architectural styles. Over the millennia, ice, wind and water have worked on the geology to produce a stunning variety of different landforms. Particularly noteworthy are the karst terrains of the Pennines and southern Cumbria, the dune fields of the Cumbrian coast, and – best-known of all – the glacially eroded U-shaped valleys, cirques, tarns, ribbon lakes and hanging valleys of the Lake District (Figure 5)

Figure 5 The landforms of the Lake District show many classic features of glacial erosion. This aerial photograph shows Blea Water Tarn, occupying a pronounced cirque on the east side of the High Street Ridge. The U-shaped valley of Riggindale lies to left. Haweswater reservoir can be seen left middle distance. (Photo: Stuart Holmes)

Some Classic Cumbrian Geological Localities

Cumbria contains more than its fair share of geological localities valued either for their significance in the history of geological science, as exemplars of geological or geomorphological phenomena, or as localities where generations of geology students learn their craft.  The county has 70 SSSIs listed purely for their geological significance, and a further 38 for combined geological/biological interest. Taken together this is the largest number of geological SSSIs of any county in England. Some classic localities are described below, with a suggested further reading list, and some selected references for those who wish to explore more advanced information on the localities listed.

The Skiddaw Granite and its Metamorphic Aureole

The Devonian Skiddaw granite pluton was intruded into folded Skiddaw Group mudstones around 390 million years ago, during the final phase of the Acadian Orogeny. A walk from Threlkeld to Sinen Gill provides a classic cross-section through the southern part of the c. 10 km diameter metamorphic aureole, with an outer zone of andalusite slates (Figure 6), and an inner zone of cordierite-rich hornfels, and the country-rock contact with the granite itself (Figure 7), all well exposed at numerous locations. The cleavage and folding in the slates has been overprinted by the effects of thermal metamorphism, indicating that the intrusion post-dates the main period of Acadian tectonic compression (Woodcock et al 2019).

Figure 6 A cleavage surface of andalusite slate from the metamorphic aureole of the Skiddaw granite. Some crystals are seen as white squares, rather than needles. This is because we are seeing them in cross-section – they have grown at right-angles through the cleavage, indicating that they formed after it. (Photo: Ian Francis)
Figure 7  The exposure of the Skiddaw granite forms a prominent waterfall in Sinen Gill.  (Photo: Ian Francis)
Figure 8 Tight folding in Skiddaw Group hornfels, Sinen Gill. (Photo: Ian Francis)

Polyphase Folding in the Skiddaw Group, Mosedale

The complex polyphase folding in Skiddaw Group hornfels, beautifully exposed along the banks of the River Caldew in Mosedale, is described by Roberts (1992)  as “as one of the finest sets of fold structures in the country”. The pattern of folding in the area may indicate that early (pre-Caledonian)  soft-sediment gravity folds have been re-folded during the later stages of the Caledonian Orogeny.

Figure 9 Polyphase folding in Skiddaw Group hornfels exposed on the banks of the River Caldew, Mosedale. (Photo: Ian Francis)

The Porphyritic Andesites of Eycott Hill

This is the type locality of the Eycott Volcanic Group, approximately coeval with the Birker Fell Formation of the Borrowdale Volcanic Group in central Lakeland (Millward et al 2000) .  A series of andesite and basaltic andesite lava flows, dipping to the east, display particularly well-developed trap topography (Figure 10). Some of the lower andesite flows display spectacular porphyritic texture, with grey or blue-grey feldspar crystals in a in a dark grey groundmass (Figure 11).

Figure 10 Aerial view of Eycott Hill, looking southeast, showing trap topography. Each line of ridges marks a separate lava flow. Above the lavas are Carboniferous limestone beds, which lie beneath the flat green fields (top left). In the top right of the image are Great Mel Fell (in shadow), with the Ullswater fells in the far distance. (Photo: Stuart Holmes)
Figure 11 Polished section of the Eycott-type porphyritic andesite. The largest feldspar crystals have long axes of about 2cm. (Photo: Peter del Strother)

Peperites on Fleetwith Pike

Around Honister Crag (Buttermere), a series of southeast-dipping andesite sheets, most of which are thought to be sills, were intruded into a thick sequence of unlithified volcaniclastic lake-bottom muds (Figure 12).  Several locations, including Hopper Quarry (pictured) show exceptionally fine examples of peperitic texture (Figure 13), caused when molten andesite lava came into contact with water-saturated sediment, resulting in explosive generation of steam and fragmentation of the magma margins (Tuffen, 2008).

Figure 12 A series of thick andesite sills, separated by thinner beds of volcaniclastic sandstone (the famous Honister Slate), give rise to the distinct layering seen on Honister Crag, viewed from Dale Head.  The beds were originally horizontal but have since been tilted to the south by Earth movements. (Photo: Ian Francis)
Figure 12 Peperite at Hopper Quarry, Honister.  Andesite magma forced its way into waterlogged sediment , causing the water to boil explosively. This shattered the top of the sill to produce a peperite –  a mixture of dark andesite fragments surrounded by light-blue fine-grained sediment.  (Photo: Ian Francis)

Volcanic Rocks on Crinkle Crags

Late Caradoc volcanism produced a 6 km thick series of pyroclastic and volcaniclastic deposits, well exposed in the craggy central fells of the Lake District. Parts of the volcanic succession are associated with the collapse of several calderas, the largest of which is known as the Scafell caldera.  The collapse was accompanied by a series of violent eruptions (Branney, 1991), the largest of which involved the ejection of at least 100 km3 of andesitic pyroclastics. These rocks are particularly well exposed on the slopes of Crinkle Crags and Pike O’Blisco in the form of thick air-fall tuffs and ignimbrites.

Figure 13 Air-fall tuff in the Borrowdale Volcanic Group Whorneyside Formation, Crinkle Crags. (Photo: Ian Francis)
Figure 14 Ignimbrite tuff in the Borrowdale Volcanic Group Whorneyside Formation, Crinkle Crags. (Photo: Ian Francis)

Silurian Turbidites at Eccle Riggs Bank Quarry

Sole marks on the base of a vertically inclined turbidite bed in the Silurian Gawthwaite Formation (Coniston Group) is superbly exposed in this quarry (also known as the ‘Donkey Rock’ quarry). See Stone et al (2010).

Figure 15 Turbidite sole structures on the base of a Windermere Supergroup (Coniston Grit Formation)  sandstone bed (originally horizontal but tilted into a vertical position by Earth movements). The sandstone was deposited by a turbidity current which scoured grooves as it flowed over the muddy sea floor. As the current slackened it deposited its load of suspended sand, filling the grooves. In this quarry face, the mud layer into which the grooves were cut (in effect the mould) has broken away and we see the base of the sandstone bed as the groove fillings (the cast).  Eccle Riggs Bank (or ‘Donkey Rock’) quarry, Broughton-in-Furness. (Photo: Ian Francis)

The Karst Landscapes of Orton Scar

Cumbria has several nationally important areas of karst landscape, of which perhaps the most important is found at Asby Scar, northeast of Tebay. Here the Carboniferous Great Scar limestone forms some of the finest limestone pavement found in Britain.

Figure 16 Aerial view of limestone pavement on Orton Scar. The rectilinear pattern of clints and grikes comes about as a result of preferential weathering along pre-existing joints in the Carboniferous  Limestone.

The Basal Permian Unconformity at Saltom Bay, and the Triassic Sandstones of the St Bees Heritage Coast

At Saltom Bay, south of Whitehaven, a wave-cut platform displays a superb exposure of the Carboniferous/ Permian unconformity. Cross-bedded grey-brown sandstones of the Upper Carboniferous Westphalian C show an abrupt erosive surface upon which lies the basal breccia of the Permian (known in Cumbria as Brockram).  Above the wave-cut platform, low cliffs give a good exposure of the overlying Permian Saltom Dolomite member of the Permian St Bees Evaporite Formation (Jones & Guion, 1990)

Figure 16 At Saltom Bay,Carboniferous sandstones (Westphalian) form the wave-cut platform in the foreground, and are overlain unconformably by a reddish brown Permian conglomerate, known locally as Brockram.  The low cliff in the background is formed from beds of the fossiliferous Saltom Dolomite. (Photo: Ian Francis)

South of Saltom Bay the Triassic St Bees Sandstone forms impressive cliffs, with extensive exposure of massive cross-bedded red sandstone, with thinner intervening shale horizons.  The sandstones are also seen Birkham’s Quarry, next to the coastal path on the cliff tops, where cross-bedding, clay rip-up clasts , and ripples are all well exposed on sandstone blocks around the quarry entrance, where there are also informative interpretation boards.

Figure 17 Ripple marks on a bedding surface of the Triassic St Bees Sandstone at Birkham’s Quarry on the cliff-tops south of Whitehaven (Photo: Ian Francis)

High Cup Nick, and the Whin Sill

One of Cumbria’s most famous geological localities is the Pennine valley of High Cup Nick, between Dufton and Murton Fells.  Here the Whin Sill dolerite (of late Carboniferous/early Permian age)  forms an impressive palisade of columnar-jointed crags around a deep U-shaped glaciated valley, with views westwards towards the Eden valley and the Lakeland Fells beyond.

Figure 18. The eastern extremity of the glacial trough of High Cup Nick, with the columnar jointed Whin Sill dolerite forming the prominent line of crags (Creative Commons: photo by Robert J. Heath)

Moraines in Ennerdale

Many Lakeland valleys contain examples of  moraines, presumed to be of Younger Dryas age. Those at the head of Ennerdale valley have long been regarded as ‘one of the finest moraine-mound (‘hummocky moraine’) complexes in England (Graham & Hambury , 2007).

Figure 19 Hummocky moraines at the head of Ennerdale valley. Black Sale YHA (middle top) gives scale. (Photo: Stuart Holmes)

Classic Features of Glacial Erosion on Helvellyn

The Lake District is one of the best places in Britan to appreciate the geomorphological effects of upland glacial erosion (Wilson, 2010).  Cirques, arrêtes, hanging valleys and ribbon lakes abound  throughout the region, but one of the finest collection of such features can be seen on the Helvellyn massif, where a series of cirques and intervening arrêtes occupy the eastern slopes of the range.

Figure 20 Ice has sculpted a series of pronounced cirques with intervening arrêtes on the east flank of the Helvellyn range. Red Tarn is just visible beyond the arrête known as Striding Edge. (Photo: Stuart Holmes)

References

Branney, M J, 1991. Eruption and depositional facies of the Whorneyside Tuff Formation, English Lake District: An exceptionally large-magnitude phreatoplinian eruption. Bulletin of the Geological Society of America, 103, p.886-897.

Goldie, H. 1996 The limestone pavements of Great Asby Scar, Cumbria, UK. Environmental Geology 28, 128–136

Jones, N.S., and Guion, P.DF., 1990. The Westphalian and Permian Geology of the Whitehaven Area. In Moseley, F. (Ed)  Geology of the Lake District Geologists’ Association Guide pp.178-185

Millward, D,   Marriner, G. F., and Beddoe-Stephens, B. 2000 The Eycott Volcanic Group, an Ordovician continental margin andesite suite in the English Lake District. Proc Yorks Geol Soc 53.

Roberts, D.E. 1992 in Treagus, J.E. (Ed) Caledonian Structures in Britain. Geological Conservation Review Series. Chapman & Hall

Stone, P, Millward, D, Young, B, Merritt, J W, Clarke, S M, McCormac, M and Lawrence, D J D. 2010. British regional geology: Northern England. Fifth edition. Keyworth, Nottingham: British Geological Survey.

Tuffen, H. 2008. Honister and Haystacks. Exploring Lakeland Rocks and Landscapes, Beale & Dodd, (Eds) pp 126-134 The Cumberland Geological Society.

Woodcock, N.H., Soper, N. J, and Miles, A. J. 2019 Age of the Acadian deformation and Devonian granites in northern England: a review. Proc Yorks Geol Soc 62

Resources

Web Resources

The late Clive Boulter produced an excellent, up-to-date, overview of Lake District geology for those with a geological background, with particular emphasis on the Borrowdale Volcanic Group.

The Cumbria GeoConservation Group has a useful website, including a map of Cumbria with placemarks for Local Geological Sites, and other Sites of Special Scientific Interest, as well as summaries of the features of each site. They have also published a variety of useful Geotrails.

​The Lake District National Park website has some useful geological information here.

​Chris Wilson has produced a nicely illustrated set of .ppt slides dealing with the geology of the Keswick area , including a useful guide to the town’s building stones.

​For those with a geological background, the British Geological Survey hosts plentiful on-line resources, such this general introduction to the geology of Northern England.

​Michael Hambrey’s brief introduction to the glacial history of the Lake District written for the Cumberland Geological Society (see also Societies).

​The Lake District National Park’s latest landscape character assessment document.

UNESCO’s web pages for the Lake District World Heritage Site

Ian Francis has produced a website which  includes an illustrated glossary, excursions, a list of Norse landscape words, and a link to a Google Earth Lakeland Geology project.

Further Reading

General Lakeland Geology

The Lake District: Landscape and Geology by Francis, Holmes & Yardley,  Crowood Press 2022

A highly illustrated non-specialist introduction to the geology and scenery of Lakeland.

Lakeland Rocks by Alan Smith, Crowood Press, 2019

Excellent illustrated descriptions of the region’s different rock types.

Geology in the Lake District National Park by Phil Davies, Otley’s Steps 2018

A guide to 32 key geological location in the National Park.

British Regional Geology: Northern England. Fifth edition by Stone, P, Millward, D, Young, B, Merritt, J W, Clarke, S M, McCormac, M and Lawrence, D J D, British Geological Survey, 2010

Detailed geology of the region for more advanced readers.

Earth, Water, Ice and Fire: Two Hundred Years of Geological Research in the Lake District by

David Oldroyd. Geological Society Memoir No. 25. The Geological Society, 2002.

A scholarly account of the history and development of Lake District geology.   

The Geology of the Lake District, by F. Mosely (editor), Yorkshire Geological Society, 1978

A detailed overview of key aspects of Lake District geology aimed at relatively advanced readers. Some details now rather dated.

Geology Guidebooks

Cumbria Vols 1 (Cumberland) and 2 (Westmorland and Furness)  Richard Wigley (Ed) Geologists Association Guide No 77 2023

The most up-to-date and comprehensive guide currently available.

The Coast-to-Coast walk: Rocks and Scenery, by Butler & Gunner, 2qt Publishing, 2017.

The first chapter (Cleator to Shap) covers much interesting Lakeland geology along C2C route.

Rock Trails Lakeland by Paul Gannon, Pesda Press, 2009.  Useful general geological introduction, with geological trails for the experienced fell-walker.

Exploring Lakeland Rocks and Landscape by Susan Beale & Mervyn Dodd (editors), The Cumberland Geological Society, 2008

A successor to the 1992 volume (see below), this time in colour, with seventeen new geological excursions.

Lakeland Rocky Rambles by Bryan Lynas, Sigma Leisure, 1994

Lake District rocks and how they formed introduced in 10 well-chosen ‘rambles’.

Lakeland Rocks and Landscape: A Field Guide by Mervyn Dodd (editor), The Cumberland Geological Society,  Ellenbank Press, 1992

Eighteen field excursions to key geological localities, still relevant today.

Geology of the Lake District by Frank Moseley (editor) The Geologist’s Association, 1990

Geological excursions to 25 key localities for more advanced readers.

Lakeland Geology: Where to Go and What to See by E.H. Shakleton, Dalesman Publishing 1987

A beautifully written introduction to the region’s geology, with 13 excursions.

Mines, Minerals, and Quarries

The Red Earth Revisited: An Introduction to the Iron Mines and Iron Industry of Furness by Cubbon, Sanbach and Woollard, CATMAS, 2021

Industrial history rather than geology, but very well researched.

Slate Mining in the Lake District by Alastair Cameron, Amberley Publishing, 2016

Ore Mining in the Lake District by Alastair Cameron & Liz Withey, Amberley, 2017

Companion volumes giving brief histories of mining and quarrying in Lakeland with excellent location photos.

The Lakes and Mines Guide by Ian Tyler, Blue Rock Publication, 2006

A brief but comprehensive catalogue of Lakeland mine locations.

Goldscope and the Mines of Derwent Fells by Ian Tyler Blue, Rock Publications, 2005

Carrock and the Mines of Skiddaw and Blencathra by Ian Tyler, Blue Rock Publications, 2003

The above two books provide the most detailed and comprehensive accounts of the history of these important mining regions of northern Lakeland.

Mines of the Lake District by John Adams, Dalesman Books, 1998

Probably the best non-specialist guide to the region’s mines and their history.

Minerals of the English Lake District: Caldbeck Fells by Cooper & Staley, British Museum (Natural History), 1990.

A beautifully illustrated catalogue of minerals from the world-famous Caldbeck mines.

Coniston Copper Mines: A Field Guide by Eric Holland, Cicerone Press, 1981

A brief guide with hand-drawn sketch maps to the mines of Tilberthwaite and Coniston

Industrial Archaeology of the Lake Counties by Marshall & Davies-Shiel, Michael Moon, 1979.

Has an excellent overview chapter on mining and quarrying.

Mining in the Lake Counties by W.T. Shaw, Dalesman Publishing, 1970

An account of Lakeland mining history, with details of some the region’s key mines written by a local mining engineer living when some of the mines were still active.

Burlington Blue-Grey by Stanley Geddes, Published by the author, 1975.

The definitive history of Burlington’s Kirkby-in-Furness quarries.

Mines and Mining in the Lake District by John Postlethwaite 3ed 1913, Moss & Sons, Whitehaven.

Perhaps the most celebrated account of the region’s mines and quarries in their heyday. Copies can still be found on ebay, including the 1976 re-issue by Michael Moon’s bookshop.

Glacial Geology and Geomorphology

The Quaternary of the Lake District Field Guide Edited by McDougall & Evans, Quaternary Research Association 2015

Good (but advanced) guide to Quaternary processes and landforms in some key Lake District localities.

Lake District Mountain Landforms by Pete Wilson, Scotforth Books, 2010

An excellent, well-illustrated,  general introduction to Lakeland geomorphology with an emphasis on glacial features.

Classic Landforms of the Lake District by John Boardman, The Geographical Association 1996

Brief but well-illustrated introduction to Quaternary landforms and processes, suitable for A-level geography students.

The Ice Age in Cumbria by Alan Smith, Rigg Side Publications 2008

An excellent introduction to how the Ice Age helped created Lakeland’s landscape features.