This is a simple EarthCache
All you have to do to claim a find is to visit the location given, gather a little information and answer some questions.
Please either email or message the answer to me.
The terrain is a little uneven but with perseverance it is wheel friendly.
You are invited to claim your find and send message with answers the same time.
Cobbles and Cobbled streets are an iconic and much loved part of British life. The sound of cars driving, bikes rolling, even horses clip clopping over them is something that is familiar to us all, and the strange and unique feeling of them underfoot is a sensation never to be forgotten. But have you ever stopped to wonder why the cobbles are there in the first place? What they do, what is their function, who came up with the idea, and when?
They are part of the landscape, lovely to look at, heart warming when you come across them unexpectedly, and something that offers up an instant hot of nostalgia for a time that is almost out of living memory now.
The word ‘cobblestone’ itself comes from the English word ‘cob’. Think of cob loaves, bacon cobs, or even cobnut – the image that comes to mind is of a small, round, lumpen shaped item. So it is no wonder that the stones used in constructing roads, those small, round, lumpen shaped ones, were known as cobbles. The term was first used in the beginning of the fifteenth century, when new roads were being constructed up and down the country. Workers had the job of wading through rivers and streams, ducking down into the chilled waters, and plucking out the roundest, sturdiest pebbles. These were the cobble stones (later cobblestones) that would be used to lay the roads.
Later, the term ‘cobble’ came to mean any rounded stone that was between 2.5 and 10 inches across, but at the time of the road laying, there were no measurements taken. Everything was done by eye, and fitted together like a long and arduous jigsaw.
So to the EarthCache
At the location given I’d like you have a good look at the cobble stones you are standing on and think about the sandstone they are made of.
Sandstone such as at this location is made when silt and mud is laid down with a consistent water flow. Sandstone (sometimes known as arenite) is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed quartz and/or feldspar because these are the most common minerals in the Earth's crust and the rock feels rough. Like sand, sandstone may be any colour, but the most common colours are brown, yellow, and red. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs.
At this location you will notice that the layers of cobbles are quite varied. Some are up to 15cm of constant colour making it look like the cobble is a single piece of stone. However there are also some cobbles which are breaking, making these cobbles of look like several thin layers of stone which the cobble is made of.
Why is there a variety of cobble quality? (You don’t need to answer this question)
These stones have almost certainly been quarried locally, in fact if you explore the quarries to the east of here there are some which have piles of cobbles ready to load up and take away. It seems that from a single quarry a varied quality of stone can be found.
So what is the determining factor to the quality of cobble? (You don’t need to answer this question)
As sandstone is laid down in a valley or a delta the quality and strength of the rock is determined by the material that is deposited. Sandstone is made from small pieces of rock that that is washed down by a river eroding the rock it flows over further upstream.
If the water flow is constant and regular it is likely that the material washed down will be constant leading to strong thick layer of stone, resulting in a cobble that is strong and a single stone. A cobble created in this environment will be very durable and even a hundred years after being set in the road it will still be a single rock.
If the water flow is variable, with flood followed by less flow the rock will be less constant in structure. The rock will have many layers or bedding planes. The intermediate layers may be weaker than the layers of rock meaning that the resulting cobble will be more prone to weathering and erosion. On these stones it is possible to see where some stones have completely de-laminated and the cobble seems to be made up of several thin sheets of stone. They clearly were laid down as a single stone however.
Cobbles are always laid so that the bedding planes are vertical so that road builders can use stones which may break along the bedding planes and still provide an even surface. If they were laid with the bedding planes parallel to the road surface and sheets broke off this would result in holes in the road.
So having read the information above, now it’s time to answer some questions.
- At the location given please describe a variety of cobbles with different properties described above.
- Was all the stone here used for cobble laid down in a similar water flow? Please explain your answer
- Are the cobbles all placed with the bedding planes parallel? Please explain your answer.
- On average many cobbles wide is the road, +/- 2?
If you feel willing and able you may include a photo with your log but please do not include any close up photos of the cobbles.
Thank you for visiting this location and attempting this EarthCache, please email or message your answers to me and you may log your find at the same time.
Happy caching
treboR