Ruskin Museum
Coniston, Cumbria.
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The Museum has a geology display by the British Geological Survey which includes rock samples from the Coniston area which can be handled and inspected. A folder is on hand to provide more in-depth geological information.  
Please note:
We now have the new 1:25,000 scale geology map of the Coniston Fells produced by the British Geological Survey on sale price 9:95p

Geology & Coniston

Coniston is fortunate in that there are two totally different rock groups represented in the area. Each "rock group" is made up from a number of different rock "formations". This variation in rock types makes it an interesting location for the amateur geologist or interested fell-walker.

The geology of the Coniston area is best viewed from somewhere like Grizedale Forest, which is to the east of Coniston. The terrain from the forest to west of Coniston consists of wooded, agricultural land, with gentle rolling hills of relatively low relief. The rocks underlying this area are marine sedimentary rocks from the "Windermere Supergroup".

There is then a major change to a bracken-covered area with few trees, steep, craggy, rocky terrain and mountains. All of the rocks here are of volcanic origin. They are part of the rock group known as the Borrowdale Volcanic Group (BVG).


Looking to Coniston Village and the Coniston Fells
Rocks below the red line are sedimentary, above are volcanic

Volcanic rocks of the Coniston Fells were laid down around 460 million years ago. The total thickness of the BVG laid down in the Lake District is over 7km, yes 7km thick, a staggering amount.

After the volcanic period the area subsided beneath the sea. In sub-tropical shallow waters teaming with marine life, the Coniston Limestone was laid down. This was not the limestone frequently seen from the Carboniferous period but a less pure limestone from the much earlier Ordovician. Slowly the sea deepened and over a long time period large amounts of muds and sands were deposited. These are the Windermere Supergroup sediments that are also of great thickness.

Due to the collision of two continents some 420 million years ago the rocks have been intensely heated and squeezed. They have also been uplifted and now the once horizontal beds dip roughly south east at up to 90 degrees. This means that if you walk up the coppermines valley the rocks get older the further you walk. Or to put it another way, you are walking back in geological time.

The other major event that affected the area in a big way happened about 2 million years ago. This was the start of the ice age. Successive glaciations carved out the valleys and scooped out hollows where now tarns such as Low Water and Blind Tarn are. This mountain and valley terrain is what makes the Lake District so special.

Coniston Rocks



VOLCANIC ROCKS: Hammer is 23.5 cm long.                                                     
Both outcrops above are from the same rock formation. Huge outpourings of air fall tuff and pulverised rock fragments were blasted out, blanketing large areas of land.  
LEFT: Thinly spaced, parallel beds of ash. The once horizontal beds have now been uplifted and dip towards Coniston at near vertical. Note no bedding at the left end.
RIGHT: Devoid of any bedding. A mass of angular to subrounded clasts from a Pyroclastic flow.  


VOLCANIC ROCKS
:
The outcrop on the right has the impressive name of a volcaniclastic sandstone. It consists of silt and sandstone size particles of volcanic origin, deposited into a shallow lake formed from a caldera. This is a slate outcrop of the type used for roofing tiles, slabs etc. In the centre you can see the bedding which is tilted to around 45 degrees (by the hammer). Below it the rock is quite smooth and has a smaller grain size than the darker, course material above.     


 

SEDIMENTARY ROCKS
Although a new name has now been given to this rock it is still widely referred to as the Coniston Limestone. It is not an extensive outcrop and it rests uncomfortably on the BVG.
Dip of the beds can be clearly seen. The obvious gaps or hollows are where the purer limestone beds  (calcium carbonate) have been more easily dissolved than the more resistant ribs.
Small fossils and corals can often be found in the screes beneath the outcrops.