Therefore, perhaps it is no suprise that T. Ryan Somerville began quarrying here exactly 53 years before the day I was born. A second quarry was built close by and today both are operated by Tarmac Ltd and from here you have a view over the extensive works that have taken place over the last 83 years of quarrying, and take the opportunity to actually view the exposed limestone sequence. Originally one quarry produced lime while the other produced construction materials and asphalt. Today, Tarmac have combined both to extract limestone.
Hillhead Quarry is currently used every two years for the Hillhead Show where over 400 exhibitors promote the latest plant equipment and services and 20,000 people attend to see live quarry demonstrations. This rich limestone in Hillhead is reserved for future extraction.
Limestone makes up about 10% of the total volume of all sedimentary rocks. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses, including as a building material, as aggregate to form the base of roads, as white pigment or filler in products such as toothpaste or paints, and as a chemical feedstock.
Geology
The part of the sequence seen at Hillend was deposited over 300 million years ago during the Paleozoic. The rocks here belong to the Carboniferous Limestone Series and are sub-divided into a regionalised sequence, which you will learn about when you visit the given co-ordinates. A lava bed sits within the sequence which includes clay wayboards that can cause problems for anyone extracting the rock. A photograph will point out the area where you can see one of these faults from the co-ordinates.
The Earthcache
To log the find, please visit the given co-ordinates. You need to enter the area from the parking co-ordinates given below. Tarmac have recently rebuilt the drystone wall that runs along the roadside and it has a fence above it. Under no circumstances attempt to climb over it. The parking co-ordinates are the point at which you will find a gate onto the footpath that runs alongside the road. Alternatively, you can walk to the location from a variety of directions. On arriving at the co-ordinates you will find an information board which will provide you with the answers to the questions below. I am aware as of 2019 it is not in a great shape but the link here may help. Please e-mail me the answers, do not include them within your log. A photograph with your log is now mandatory.
Questions (answers to be e-mailed)
1) Looking at the provided diagram, coming NE to SW, name in order the 4 limestone sequences, named after their respective dales.
2) Of the 4 limestones sequences previously mentioned, which sequence has the greatest thickness?
3) The illustrated diagram will show you roughly the area where you can see the lava fault as you look across the quarry. You need to study the stone sequences and tell me the difference you can see between the lava fault and the limestone sequence.
4) From what two minerals is limestone largely compromised, and these are different crystal forms of what? (You will need to research elsewhere for this answer).
5) Because of the situation with the noticeboard, from 2023 a photo of yourself or a personal item with the quarry view or edge of the noticeboard is now a mandatory requirement for logging. Please ensure you submit one to prove you have been the the listed coordinates. Thank you.