This feature provides a wonderful introduction to the types of rocks likely to be encountered in this region.
We shall be concentrating on Limestone which is prevalent in this area and quarried locally. Limestone exists from Lochaber to Glen Nevis, Loch Eil and onward. Either stratified with a dark blue colour or veined. Specimens of clay and stone marl can also be found in the area, together with calcareous petrifactions caused by powerful springs. The same limestone composes a great part of the mountains to the SW.
So what is Limestone, well it is a sedimentary rock - mostly formed of grains of skeletal fragments of marine life. It also contains varying amounts of silica, clay silt and sand which gives limestone its variants of colours. Formed in shallow seas millions of years ago as the grains settled and together with the action of pressure and heat produced the rock that you see today. Limestone makes up about 10% of the total volume of all sedimentary rocks. Soluble due to its grainy construction, thus forming many erosional landforms that you may have seen, from limestone pavements and pot holes to caves and gorges. Despite this, limestone is more resilient than most other sedimentary rocks.
It is therefore usually associated with hills and downland, and occurs in regions with other sedimentary rocks, typically clays. Being easy to quarry it is a popular building material as well as being the raw material for quick lime - used in cement and mortar. Powdered lime is used to neutralise soil by gardeners before growing vegetables or crushed limestone is used as aggregate.
Limestone is particularly suited to sculptors and it also has a variety of other uses, so indeed a versatile rock.
Find the large example of limestone rock here that has been quarried just north of Fort William. Take time to look over its surface and notice its structure, read the information board and answer the following .....
1. What number is the limestone rock in the feature?
2. How many million years ago was it formed in the shallow seas?
3. Take time to look around the rock at its surface texture and list what you see.
4. What quarry did this rock come from?
5. Please take a picture at one of the other rocks and add to your online log.
6. Now simply email or message us privately with your answers and log your experience online.
More information on Earthcaches can be found here. http://www.geosociety.org/earthcache/intro.htm