Welcome to Thurso, the furthest North railway station in Scotland. Appropriately, the railway line from Inverness to Wick and Thurso is known as the Far North line. This is an EarthCache. As such, you will not be looking for a physical container, but will work through an Earth Science lesson. In this instance, the lesson is about the rock used to in the construction of the station building and some of the physical properties of it.
The station opened on 28th July 1874, as part of the Sutherland and Caithness Railway. Originally built with a small goods yard, engine shed and turntable, it was used extensively during both World Wars to transport personnel and materials to Scapa Flow and, in the 1950s for the construction of the nuclear research facilities at Dounreay. The turntable was removed in the 1950s and the engine shed was removed prior to the introduction of diesel services in 1961. The station building is Listed as Category B.
The station building is constructed from local sandstone, with a mainly timber roof. However as this is an EarthCache, so we will be ignoring the roof structure!
Sandstone is a sedimentary rock. This means that it is formed following the deposition of sediment, which are then overlain by successive layers of sediment. Over time, this builds up and the enormous pressures due to the weight of the layers above mean that the sediments are compressed together, any water forced out and the resulting rock is held together by the minerals that remain. Through observing cross-sections of the sedimentary rock, we can often see different colours. This is due to either changes in the source of the original sediments, or changes in the minerals within the rock, or both. Primarily it is due to the changes in the source material of the sediments.
Depending on the length of time over which each layer of sediment was deposited, the layers can be a few millimetres in depth or they can be a metre or more. The layers can be most easily distinguished when the sediment source material changes, leading to a change in colouring or sediment grain size.
Considering the front of the station, we're going to look at the section of wall between the right hand corner of the building and the rectangular window. To the right of the window, there is a rusty metal ring. Counting up the wall, the block of stone immediately above it is block 1. Look at block 2.
Q1) Can you please describe the appearance of the block? Particularly, can you describe any changes in the appearance between different sections of the block?
Q2) Considering what is discussed above, what could be the reason for these changes?
Now we will consider the physical properties of the stone. As sandstone is made up of discrete grains held together by minerals, and was formed through immense pressure compressing the grains together, then it is naturally strong in compression (when the grains are being squashed together). It is not good in tension (when the grains are being pulled, or forced, apart).
We will now look at the corner of the building between the station entrance and the Royal Mail post box. Specifically, the metal items embedded in the wall. These have corroded over the years and, as iron oxide needs more space than the iron or steel metal, then it tries to expand.
From the large item, look two blocks below at the small metal item. There is a crack running from this item.
Q3) What direction does it run? Approximately how wide is the crack?
Q4) Given the size of the metal item embedded in the wall, does the effect on the stone indicate that the stone is weak or strong when subject to tension forces?
One last thing before you go... Please go to the Waypoint "Photo Location - Stage 2" and take a photo of yourself or a personal item showing the trefoil-shaped grille at the top of the wall and the sign that has only two words on it that is between the two main windows.
Finally, please send me the answers to Questions 1 to 4 via the Geocaching Messaging system or via e-mail and then upload the photo with your log.
Thank you for visiting SideTracked Thurso, the most northerly SideTracked cache in Scotland.
About SideTracked Caches
This cache belongs to the SideTracked series. It is not designed to take you to a magical place with a breath taking view. It's a distraction for the weary traveller, but anyone else can go and find it too. More Information can be found on the SideTracked Series website at www.sidetrackedseries.info https://www.sidetrackedseries.info