The Lake District's geology is complex but well-studied. Its oldest rocks are the Skiddaw Slate series and the Borrowdale Volcanic series dating back to the Ordovician, some 500 million years ago. The Skiddaw Slates are found in the northern part of the park and were probably deposited in shallow seas; their thickness is unknown. The Borrowdale Volcanic rocks are more extensive and form the Lakes' highest peaks, being resistant to weathering. Later intrusions have formed individual outcrops of igneous rock in both these series. The other large rock group is the Silurian Windermere Group, made of Limestone that rests upon the volcanic rocks. Many smaller series are also present.

All visitors to the Lake District are struck by the beauty, grandeur and variety of the scenery, but few appreciate the extent to which this has been influenced by the underlying rocks and the natural processes shaping their surface. Yet the geology is there for all to see in the form of crags, road cuttings, and rocky knolls in abundance. Evidence of man’s exploitation of geological materials is also widespread, with numerous abandoned mines and quarries together with a number of active quarries. The local stone is used in buildings and walls that help to give the landscape its character. Most striking of all, there is the magnificent contrast between fell and dale, the result of glacial action during the last few thousand years.

Distribution and Origin of the Rocks of the Lake District

The bulk of the National Park is made up of three broad bands of rock trending from SW to NE. The rocks which form the mountains and hills are not necessarily ‘harder’ than those which form adjacent lower land. The Lake District rocks are ‘buoyed up’ by sitting ‘astride’ a ‘batholith’ or ‘raft’ of low density granite. The granite underlies the whole area and small protruding parts of it are seen at the surface as the Eskdale, Ennerdale, Skiddaw and Shap granites which are local to the Holiday Cottage. On your journey up the M6 to the cottage you will see off to your left the round "hill" of the pink granite intrusion and the quarry that used to extract it. Further along the A6 is the blue granite quarry.

The SKIDDAW GROUP is the oldest group of rocks in the Lake District. They were formed during the ORDOVICIAN period, about 500 million years ago, as black mud settling on the sea bed in relatively deep water where occasional layers of coarser silt and sand were also deposited.
The Skiddaw Group forms a roughly triangular mountainous zone in the north of the Park, reaching a maximum height of 931m on Skiddaw itself. Despite their slatey appearance, they are not suitable for roofing because they easily break into small pieces. Although there are some rugged areas developed on rocks unaffected by thermal metamorphism, such as on the south face of Blencathra, the mountains developed on SKIDDAW GROUP rocks are more typically smooth in outline.

South of the Skiddaw Group lies the BORROWDALE VOLCANIC GROUP (BVG). These rocks are volcanic lavas and ash flows (pyroclastics) erupted during a phase of cataclysmic volcanism 450 million years ago. This volcanism was caused as the Iapetus ocean SUBDUCTED beneath the continent on which present-day England was to form. The BVG lavas are mainly ANDESITES, with some BASALTS and RHYOLITES. Ash and lava fragments thrown up by the volcano settle out in the encircling waters to form TUFFS and AGGLOMERATES.
The BVG rocks underlie the highest and craggiest central part of the Lake District, including the well known peaks of Scafell (964m) and Scafell Pike (978m), Helvellyn (950m), Coniston Old Man (803m) and the Langdale Pikes (736m). The ruggedness of the terrain makes this the most popular area with fell walkers and rock climbers.

Further south again is a zone of slates, siltstones and sandstones, also formed in the sea, during the SILURIAN period about 420 million years ago. These rocks are known to geologists as THE WINDERMERE GROUP.
These rocks are less resistant than the BVG and form a belt of foothills stretching from the Duddon estuary to Kendal. They are possibly the most familiar part of the Lake District to many visitors as they lie across the A591, the main tourist route into the National Park, and include the lakes of Windermere and Coniston Water.

About 400 million years ago all these rocks were folded, faulted, intruded by molten magma and pushed up to form a very high mountain range. These events are known as the CALEDONIAN OROGENY (mountain building episode) and they were caused by the collision of two continents. 400 million years ago the Lake District mountains looked something like the Himalayas today. The Himalayas are still being formed by India colliding with Asia to build a high mountain range. The Caledonian orogeny compressed many of the BVG tuffs and turned them into the famous Westmorland green slates.
Millions of years of erosion have worn down these mountains to their present size, but the folds and faults can still be seen and the igneous intrusions, which cooled and crystallised hundreds of metres below the surface, are now exposed around Eskdale, Ennerdale, Shap, Skiddaw and Carrock Fell. They all form part of a very large granite ‘batholith’ at depth (as already mentioned) and this tends to ‘buoy up’ the whole area.

During the DEVONIAN period the high mountains were eroded to low hills and about 350 million years ago most of the land sank beneath a tropical sea. This teemed with life and the sea floor became covered with a thick layer of sediment, made up of the broken remains of shells, to form the pale grey Carboniferous Limestone. Some shells survived intact and so fossil corals, brachiopods and snails are sometimes found in the limestone.
During the latter part of the CARBONIFEROUS period this sea was eventually filled in with mud and sand and was colonised by swampy forests whose remains now form coal. Most of these rocks lie on or just outside the National Park boundary.

About 280 million years ago the Carboniferous rocks were uplifted and folded into a broad dome by another orogeny, the VARISCAN OROGENY (its most severe effects were felt in what is now Devon, Cornwall, South Wales and South West Ireland). After the Hercynian mountain building episode the Carboniferous Limestone was left as a broken rim girdling the higher mountainous core. The limestone takes the form of a long curved cuesta around the northern edge of the National Park and a more broken zone in the south, lying only partly within the National Park. It contains two very prominent west facing scarps, Whitbarrow Scar and Scout Scar, both situated to the west of Kendal.
Since the formation of the Skiddaw Slates Group during the Ordovician period, the part of the Earth’s crust we now call the Lake District has been slowly drifting north, starting from a position well south of the equator. During the late Devonian, or early Carboniferous, it crossed the equator and by about 250 million years ago it reached the latitude of the present day Sahara Desert.
A landscape of sand dunes and salt lakes developed, with seasonal downpours of rain washing rock debris from nearby uplands onto stony plains. These conditions persisted throughout the PERMIAN and TRIASSIC periods and ended about 190 million years ago.

The St. Bees and Kirklinton Sandstones to the west and north of the National Park were formed at this time and are thought to be the result of ‘flash floods’, whereby a mass of sand or larger debris is deposited in a sudden downpour or storm.
By contrast, the Penrith and Lazonby Sandstones of the Eden Valley (east of the National Park), although deposited in the same eras, are desert sandstones of aeolian origin showing dune bedding and rounded grains. Since the formation of the Triassic rocks, many more rocks have formed in what is now the British Isles, but none of them are now found in the Lake District. The drift northwards, however, continued, bringing us to our present latitude.
About 2 million years ago the Earth’s climate cooled, allowing the development of glaciers and ice sheets which, at their maximum covered most of mainland Britain. These cold episodes were called GLACIALS and were separated by warmer INTERGLACIALS supporting broadleaved forests. It is believed that there may have been as many as 10 such climatic oscillations.
It is the action of glaciers and meltwater, frost conditions and slope action during this period which have shaped most of the surface detail of the Lake District and made the area a text book example of such landforms.

Following the last glacial episode the HOLOCENE commenced. This is typified by sea level changes and the development of soils. In the Lake District, grey-brown forest soils developed beneath mature oak forest at lower levels, whilst at higher altitudes MONTANE soils were formed - known locally as RANKERS. Many of the lake and estuarine basins became filled with peat. Tree clearance in the 11th Century led to soil erosion and further activity on the alluvial fans and lake deltas of the central Lake District. Since then the land surface has remained virtually unchanged.

Quarries and Mines in the Lake District

Many Lake District rocks have been quarried, mostly for use in the construction industry. There are many miles of drystone walls and numerous village buildings made of local stone which came from small local quarries.
The most important rock quarried in the Lake District is slate taken from the BVG. The most famous quarries were around Honister Pass. Various types of Granite were quarried for use as kerb stones and stone setts (cobbles). Granite was quarried near Ravenglass, in Eskdale, at Threlkeld (near Keswick) and at Shap.
Mines in the Lake District were created to exploit mineral ores which formed as ‘veins’.These mineral veins filled cracks (joints and faults) in between the surrounding rock quarried when mineral-laden groundwater cooled and depressurised as it progressively circulated through the bedrock. Veins are very unpredictable in their thickness and mineral content and, as a result, mining them was always a financial risk. Some of the more famous mines were Greenside lead and silver mine, Borrowdale graphite mines (the graphite from these mines was used to make pencils in Keswick; these were the first of their type in the world) and Coniston copper mines.

The Shap Granite is one of the best-known and most distinctive rock types in northern England. With its coarse porphyritic texture and large, pink orthoclase feldspar megacrysts, it has been quarried as a building stone used in London and many other places. Although the Shap Granite only outcrops over a small area of 5.5 km² (fig. 3), geophysical studies and field evidence have revealed that it is steepsided stock-like intrusion with a subsurface extension to the northwest. This granite pluton was intruded near and at the unconformity between the Ordovician Borrowdale Volcanic Group lavas and tuffs, and the overlying Silurian Windermere Group. The heat and hydrothermal fluids from the crystallizing granite magma as it cooled generated a broad (600+ meter wide) metamorphic and metasomatic aureole around its contact with its host rocks.

The Shap Granite intruded the surrounding host rocks as a magma that released hydrothermal fluids as it crystallized and cooled. These hot fluids in turn produced an atypically wide contact metamorphic and metasomatic aureole around the intrusion. There is no evidence at the boundary for tectonic emplacement of a primordial cold granite body. This study documents an abundance of Po radiohalos in the Shap Granite. These Po radiohalos had to have been produced in the granite after the hydrothermal fluids released in the granite had assisted in the formation of the granite’s distinctive orthoclase feldspar megacrysts, and after the crystallized granite had subsequently cooled below the 150°C annealing temperature of radiohalos. The abundance of Po radiohalos is consistent with the hydrothermal fluid transport model for Po radiohalo formation and with catastrophically rapid granite formation. These features imply that the Shap Granite formed in 6–10 days and its Po radiohalos within hours to days once the granite cooled below 150°C. Hydraulic fracturing of the host rocks overlying the pluton facilitated rapid unroofing of the granite. Continued rapid erosion then deposited granite pebbles in the basal conglomerate of the overlying limestone. It is, therefore, conceivable that the Shap Granite formed, was unroofed, and the basal conglomerate with granite pebbles was deposited, all within 2–3 weeks during the early-middle part of the Flood year. The Po radiohalos and other evidence associated with this granite thus remove objections to Flood geology and any need to place the Flood/post-Flood boundary in the lower Carboniferous.

Why are there so many lakes?

The Lake District has over fourteen lakes and tarns. The Lake District’s volcanic rock does not allow water to seep away. The high rainfall, combined with the extra deep glacial valleys, means that the valleys are able to store large volumes of water.

If you are interested in the geology of The lake District then we can recommend the following attractions:

The Threlkeld Quarry & Mining Museum

The mine is situated three miles east of Keswick, in the heart of the breathtaking Lake District in Cumbria. The quarry and museum have been lovingly run by our knowledgeable and dedicated staff for more than ten years, and the site continues to expand through the dedication of the staff and volunteers.

The museum offers activities for all the family, from budding geologists to hopeful prospectors.

It includes:

• An underground tour of a realistic mine experience
• A comprehensive geological and mining museum
• The quarry site with a unique collection of machinery
• Mineral panning
• School or student groups welcome by arrangement
• Ample free parking, shop and hot and cold drinks

The museum is open 7 days a week from Easter to October.
Visit the Threlkeld Mine website

Honister Slate Mine

Located at the head of the Honister Pass in the centre of the Lake District, they produce the world famous Westmorland Green– a beautiful, functional material that has been extracted here for centuries. 
Our slate is 400 Million years old!

Visit Honister Slate Mine website

Conserving Lake District Geology

Some of the sites where the geology can be studied are internationally important or easily damaged by specimen collecting. The most important sites internationally and for research studies are designated Sites of Special Scientific Interest (SSSIs) which means that they are legally protected from damage. There are other interesting landscape and geological features without this protection. To help conserve geological sites a Geological Fieldwork Code has been developed. This is available on receipt of a SAE from The Geologists’ Association, Burlington, Piccadilly, London W1V 9AG. www.geologist.demon.co.uk
The Caldbeck Fells are an important part of the National Park where archaeological, geological and ecological features have been given statutory protection. To protect the important geological and archaeological features of the Caldbeck and Uldale Commons areas special permission and a permit is required for specimen collecting.