Between Torver Beck and Timley Knott there are exposures of a sequence of strata spanning the Ordovician/Silurian boundary. Rocks of the Borrowdale Volcanic Group are overlain by the Coniston Limestone Formation of the Ashgill Series, overlain in turn by a Silurian sequence.
We suggest you print the ‘map’ pic which shows the route to follow. Allow 1-1.5 hours for the trip. The hillside is rocky and steep in places so boots and the usual hillwalking gear are recommended. Take care.
Park at the beginning of the Walna Scar track, just through the gate. See the nearby LQ: cache, GC170HY if you don’t know how to find this. Once prepared for the adventure, head west along the track. At the sharp left bend, continue ahead on a grass path towards Timley Knott and the first point on our short tour.
Point 1: N54° 21.825 W03° 06.147 Here you will find several chunks of rock sticking out of the bracken and grass. They show obvious layers, some with worn away cavities. These rocks are made of Coniston Limestone and are about 440 million years old, the end of the Ordovician period. Have a good look at the rocks - texture, colour, structure, feel etc. See note 1.
Now traverse across the slope under Timley Knott and examine the rock of the crag - point 2. Again this is Coniston Limestone but you’re are looking at flatter surfaces because of the way the layers are sticking almost vertically in the air. What similarities can you see to the rock at point 1?
Continue onto easier ground and visit the large, obvious boulder at point 3 in the little stream valley. N54° 21.798 W03° 06.236 Have a close look at the rock, gently run your hand over the surface, look at the pattern of cracks and the density/type of the rock grains. Are the particles that make up the rock all the same size or are there larger ‘pebbles’ in it? Is this the same limestone or something different?
Before you head up and around to the top of the Knott, look at the side of the crag. Notice how the layers of limestone that form Timley Knott are standing up. The rock is in many beds/layers which were formed horizontally in water. They have been tilted upwards by big forces in the earth and are also slightly folded and bent. Imagine how hard it is to bend rock! Also look up to the left, above the top of the Knott and compare the rock up there with the side of the Knott. Does it look different to the limestone? In what ways?
Point 4: a steep pull up to the top of the Knott - have a pause to catch your breath and enjoy the scene spread before you. The craggy mountains are behind and the flatter, rolling landscape in front. The change of scenery is because of the change in rock types. More on this later! N54° 21.832 W03° 06.203
At the top you will be able to see the ends of the layers of limestone sticking up. Take a picture of you or your GPS by the rocks. Compare them with the first rocks you saw at point 1. Can you see some cavities in the layers? The limestone does have fossils in but they tend to be easily eroded by weathering processes, and they leave the empty cavities. The impurities in some layers also make the rock more resistant and so different layers weather at different rates. There’s a great small outcrop on the left near the top with loads of holes and cavities, looking very pock-marked.
Point 5. Ok so, hopefully, you’re getting familiar with this Coniston Limestone by now. Now we’re going to take a few steps and go back in time many millions of years! Standing on the top of the Knott, face the rising hillside towards Coniston Old Man. Walk to the edge of the rocks that continue upwards and look closely at them. What do they look like? What differences can you see compared with the limestone?
Is the rock in layers with variations like the limestone? Are there cavities and holes? You may see small areas where bits have been knocked off recently - what’s the colour and particle size like? Looking at the larger scale, what does the crag above look like compared with Timley Knott? More slab like? These are part of the Borrowdale Volcanic Group (BVG) of rocks and a fault separates the two bands of rock. See note 2.
Continue up the crag towards point 6. Take care but it’s just a gentle scramble. As you go up, keep looking at the rock. It doesn’t stay exactly the same - can you identify some changes in how it looks and feels? Near the top the rock starts to get veins of a white rock in it. Any guesses what this might be?
At point 7 you reach the quarry road. N54° 21.907 W03° 06.359 As you came up you probably noticed the rock getting rougher with a greater mixture of particle size - lumpier ash. Further up the side of Coniston Old Man is an area of rock made from consistently fine ash. After being compressed and subject to immense pressure it has developed cleavage, which means it splits easily into thin sheets. This has been quarried for many years to make into slates. At the road turn left and head back down towards the Walna Scar track.
Point 8. So, you’ve now visited the limestone of Timely Knott and the blocks and slabs of the BVG rocks. Now some easy tests to see if you’ve taken it in! At the end of the quarry road is a metal bar/gate. By the western ‘gatepost’ are two large boulders. Can you identify which type of rock they are? N54° 21.739 W03° 06.324
Point 9. Across the Walna Scar track opposite the quarry road is a small grass bank. There is an obvious small round boulder sitting on the grass. What type of rock is this one? N54° 21.721 W03° 06.286
Point 10. N54° 21.731 W03° 06.162 Now it’s time to visit the third rock type in the area. Head towards the car park and find the small outcrop at point 10. To the north, forming Coniston Old Man and the central Lakes are the BVG rocks. Then there is the thin layer of Coniston Limestone marking the boundary between the Ordovician and Silurian periods. South of the limestone and forming much of the rest of South Lakes are the Windermere Group of Silurian rocks. Beyond this are the areas of limestone from the Carboniferous period. See note 3.
Have a look at this small crag at point 10. How does this rock differ from the two other types. Fine layers? Blocky fractures? Cavities? Fine grains? Slaty pieces breaking off?
Now it’s back to the car park, which is in an old small quarry. What type of rock were they digging out?
We hope you have enjoyed your tour covering three main rock types, millions of years in time, and a pleasant scramble. Hopefully, you have developed your rock observation skills - it’s amazing what you can see and feel on close examination.
To claim this Earthcache, please post a photo with your log and email us the answers to the following questions:
- At Point 3, what type of rock is this large boulder made out of?
- At point 8, what are the rock types of the two boulders by the west gate post?
- At point 9, what rock type is this small round boulder on the grass bank?
- At point 10, can you identify and describe three differences between the Coniston Limestone rock and the Windermere Group rock?
- Please upload a photo of you or your GPS on Timley Knott next to some Coniston Limestone.
You are welcome to log your visit and send your email at the same time, however, incorrect answers or no photo may mean your log is removed.
Background notes
Note 1 - Coniston Limestone
The limestone is formed by deposition and the layers vary because sandy and muddy phases occurred along with the calcium carbonate from marine organisms. It’s more varied and much older, about 100 million years, than the limestone in places like Whitbarrow and Scout Scar near Kendal, and around the edge of the Lakes,.
The Coniston Limestone (also known as the Dent Subgroup) occurs in a thin band with a max thickness of 150m, but it can be traced from the Duddon estuary to Shap. Timely Knott is a great place to see it outcropping on the surface. Geologists like this area because the rocks occur in a way which helps understand the sequence of rocks and work out dates, events and timescales.
Note 2 - BVG
The rocks above Timley Knott, are part of the Borrowdale Volcanic Group (BVG). The limestone was formed from marine creatures, sand and mud, and the BVG rocks are from volcanoes. Lava, ash and fragmented rocks were ejected from vents, which then settled in water, so like the limestone they are sedimentary but from a very different source. The BVG rocks are also from the Ordovician period, but earlier than the limestone. Geologists think that there is an ‘unconformity’ in the sequence here, with a gap of many millions of years between the creation of the BVG rocks and the Limestone. The BVG rocks form much of the rugged central Lakes.
Note 3 - Windermere Group
The Windermere Group of rocks include coarse and fine grained sandstones, mudstones and shales, some of which have a pronounced slaty cleavage. They are also sedimentary but much younger and have been folded and compressed as the movement of the plates which make up the crust closed up the ancient Iapetus Ocean.
They cover a wide area from the Duddon to the Howgills, forming the rolling hills, with some small craggy outcrops as you saw from the top of Timley Knott. The underlying geology has a big impact on the resulting landscape, and how subsequent glaciation affected it.
Ashgill
A short distance to the SW of Timley Knott is Ashgill Quarry, which gives its name to the Ashgill Series of Marr, the uppermost series of the Ordovician. The strongly cleaved but fossiliferous rocks have enabled geologists to subdivide the succession. A locality of great historical value, exhibiting the type developments of Ashgill stratigraphical units of great importance in correlation with other areas.