Glacial Erratic - Clach Bharraig Earthcache EarthCache
Glacial Erratic - Clach Bharraig Earthcache
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Difficulty:
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Terrain:
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Size: 
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Clach Bharraig is a large boulder perched on the hillside above the road to the car park at the Cairngorm ski area. It is not marked on the 1:50k map but is shown on the 1:25k version.
It is a steep, but short climb up to the boulder from the road side. It is possible to easily leave your vehicle immediately below the boulder.
An erratic is a rock that has been carried for some distance from its original position by glacial action
The boulder is slightly rounded - this may be evidence that it was carried for part of its journey within a glacial flood or river rather than solely within or on top of the glacier that covered this area 10,000 years ago.
Geologists have suggested that landslides or rockfalls initially dropped the rocks on top of glacial ice. The glaciers continued to move, carrying the rocks with it. When the ice melted, the erratics were left in their present locations.
In some cases, boulders have been found large distances away from their "parent" rock formations. This is probably not the case with this erratic, as the rock type is the same as found in the main Cairngorm massif nearby and is typical of the reddish - pinky granite found on this, the south side of the main Strathspey valley bottom.
The road to the ski area is relatively new and was built in the 1960's. Undoubtedly some amount of explosive was used to force through part of the road to the car park. On the uphill side of the Clach (gaelic for stone or rock) is two strange star shaped depressions which are much lighter in colour than the rest of the boulder - evidence of an explosive at work?? You can also see that the rock here has been broken off at some time. What do you think?
To claim this cache, you must do two things:
1) Post a photo of yourself actually at the boulder - no distance photos allowed!!. Your GPSr must clearly be in view.
2) Estimate the mass of the boulder in kilograms. You will have to work out the volume of the boulder in cubic metres first, by "measuring" it on site. Find the length, breadth and height and multiply these three numbers together. For each cubic metre of rock, the mass is about 2.75 tonnes.
Once you have an answer, marvel at the ice carrying it there!! Email me the answer via my profile. If I do not receive the answer and/or a photo is not posted, you may have your log deleted.....
Do NOT post your answer here! This only encourages armchair cachers who have not visited.
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Please note: I no longer cache actively, but have kept these caches (Earth and Virtuals) for the enjoyment of those who do. I may not reply, therefore, to your email. If you are really looking for a reply, please don't log this cache.
Additional Hints
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