Roslin Chapel EarthCache
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Rosslyn isn’t just a beautiful example of a medieval chapel, it’s a stone carver’s dream – and it’s got a lot for a geologist to look at, too. The Carboniferous sandstone it’s built from is local, quarried in two rounds (first for the medieval portion of the church and then in Victorian times for the baptistry at the west end – you can tell the difference by the colour and weathering of the stone). The guides you can get from the visitor’s centre suggest that the medieval workers did their quarrying in Roslin Glen, while the Victorian addition might have come from Craigleith in Edinburgh. Craigleith quartz sandstone is about 330 million years old and contains features like crossbedding that indicate it was probably laid down in rivers or deltas.
Because entry to the chapel is at certain times only and you have to pay to get into the visitors centre we have chosen to bring your attention to some interesting stones in the outside wall which you can see 24/7 and for free ! And probably came from the same source as the stone used in the chapel itself.
Sandstone is a clastic sedimentary rock comprised mainly of sand particles. The size of the particles can be subdivided into very fine (0.0625 to 0.125mm), fine (0.125 to 0.25 mm), medium (0.25 to 0.50 mm), coarse (0.50 to 1.00 mm), and very Coarse (1.00 to 2.00 mm).
Clastic is defined as rock made up of broken pieces of older rocks. Sandstones are further categorised on the basis of their grain types, which can be quartz, feldspar or rock fragments (lithic).
Sandstones are deposited by a wide variety of processes, such as fluvial (river), alluvial (river), aeolian (wind) and turbidity currents (underwater currents). Like sand, sandstone may be any colour, but the most common colours are: tan, brown, yellow, red, grey, pink, white and black.
Weathering is the process where rock is dissolved, worn away or broken down into smaller and smaller pieces. There are mechanical, chemical and organic weathering processes.
The sandstone is quite badly weathered in some places along the wall, but it shows off some really beautiful cross-stratification. The North side was more affected by rain, and in places has a green tinge because of mould or lichen in the rocks. On the south side, sun and westerly winds were a big issue. The stones in the wall as well as the chapel have suffered from chemical weathering and staining from industrial pollution (particularly from coal mining, which was one of Edinburgh’s main industries in the 19th century).
To claim this earthcache, please send the answers to the questions below to us by email / message centre- do not post in your online log. Your log may be deleted if these criteria are not met. Educational guidelines for Earthcaches are set by Geocaching.com and GeoSociety.org (Earthcache) and have to be adhered to.
The co ords above bring you to a green painted door in the wall.
1) About 1m to the left side of the door and 1.5 m up are 2 thin stones, what colour are these and what caused the colour?
2) On the right hand side of the door, 2nd stone up, you will find a grey stone with white ridges. Can you explain how these ridges were formed and how they feel compared to the rest of the stone?
3) The 3rd stone up from the ground on the right of the door has an interesting pattern on it. Briefly describe the layering that you can see. What might be the cause for the patterns that you can see in the rock?
4) Keeping to the right hand side of the door about 2m along and 1.5m up are 2 red sandstone stones with clear patterned ridges. Do you think the builder of the wall has turned the stone from its original orientation when it was formed and why?
5) Look at the sculpted/ engraved stone above the door. Describe the effects of any weathering you see here and what do you think caused it?
While not compulsory it is always good to see photos from your visit
Additional Hints
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