Cawfields Quarry, named from the calls of nearby colonies of black Crows and Rooks is on the Hadrian’s Wall Trail.
Towards the end of the Carboniferous Period around 300 million years ago, movements in the crust plate on which Great Britain sits allowed molten rock, or magma, to be injected under pressure into the rock layers present over much of northern England. This molten rock then cooled, crystallised and solidified to form the Great Whin Sill – a mass of dolerite which, although mostly underground, can be seen exposed at the surface in many places today. It extends for around 1,500 square miles and underlies much of south and east Northumberland and the Durham Coalfield but its maximum known thickness of around 70 metres is under the Pennine mountains.
Where the molten rock cools relatively rapidly lots of small crystals form and the resulting rock is a fine-grained basalt. Significant contraction forces build up as it cools and while a flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form. The extensive network of cracks that develop may result in the formation of columns - very small (less than 1 cm diameter) if the cooling is very rapid, larger diameter columns if the cooling is slower.
The study of Geology began in the British Isles and many of the terms used to describe British geological features are still used throughout the world. Sill is one of those terms. Quarrymen of Northern England used the term 'sill’ to describe a more or less horizontal body of rock. ‘Whin’ was applied to dark & hard rocks and the quartz-dolerite that makes up the Whin Sill is such a rock. Because it is harder than the surrounding rocks it often occurs as outcrops and some of Hadrian’s Wall as well as Bamburgh and Dunstanbrough castles are sited on it as are many waterfalls such as High Force and Low Force
To claim this earthcache you will need to perform four tasks:
1. Estimate the height of the ridge wall, which can be seen from car-park.
2. Take photo of ridge wall
3. At N54 59.604 W2 26.973 take photo of your GPSr with this sign in the background
4. Finally, how many years ago was magma pushed up deep from within the earth?
Message the answers to the three tasks to me at the same time as you log your find. Post your pictures with your log.
Some reference should be made to the Great Wall of the Emperor Hadrian. The line of the Wall originally passed along the crest of what is now the quarry face. Of course all traces of the wall in the immediate vicinity have long since disappeared due to the attentions of bygone generations who appreciated the ready-dressed stones of the Wall when their houses, outbuildings, yards and roads required repairing. For many centuries after the end of the Roman occupation of Britain, the Wall remained more or less intact and it was not until the days of Border warfare and afterwards when the land was settled, that in places the Wall was despoiled. Life and tenure of property and stock on the Border Marches were uncertain to say the least, and the Wall provided a ready means of building stout watch towers (peels) and farmhouses.
Looking in an easterly direction from the quarry, the Wall can be seen stretching for miles along the top of the high ridge it is in this direction that it is to be seen in its greatest state of preservation. Looking North on a clear day, an uninterrupted view of miles of Bewcastle fells can be seen looking South there is the beautiful valley of the river South Tyne lying at one's feet. Truly the Romans had an eye for country and if, as recent observations tend to show, the Wall was built from Wallsend-on-Tyne on the East Coast to Solway Firth on the West Coast — a distance of roughly 70 miles — in about four years, it was an achievement in engineering skill and organisation of which we might well be proud. Bede of Jarrow informs us that the Wall was 8 or 9m.. in height and about 2.4m. in width and no great stretch of imagination is necessary to transform the now unbroken quietude to the stirring noises of activity when the Wall was a permanent camp outpost of Imperial Rome.
Please Note:- any logs which haven't met the criteria for this earthcache will be deleted.
