Logan or Rocking Stones - 'La Roche Tremblante'
Size:  (not chosen)
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Brittany's first EarthCache is a short walk into the woodland North of the 'Moulin du Chaos' Although not suitable for wheelchairs, the cache can be reached by buggies (strollers).
This EarthCache is one of a series of EarthCaches based on Logan Stones. Others in the series include:-
Logan or Rocking Stones - 'Helman Tor'(GC10PE8). (Cornwall, GB)
An interesting geological formation, often associated with granite outcrops are Logan or rocking stones, sometimes called Logans. The exact formation of these stones is the subject of several theories but it is generally accepted that Logan stones on the Tors of South West Britain were formed through selective weathering (wind, frost and rain) of granite rocks, until a part has become disjoined from the parent-rock and is pivoted upon it. Before the nineteenth century it was believed that the ancient Druids had constructed them and their strangeness has long been thought to give them supernatural associations and made them a focus for witchcraft.
Many other Logan stones around the world were formed as a result of glacial or river deposition. For further reading a good starting point is found at this link. A simple definition of a Logan stone is - a stone which is substantial, permanent, historic and can be rocked (in a see-saw action) easily by a single person
Even the origin of the name “Logan” is not well understood. It may come from the English dialect ‘log’ which means to rock (in some parts of Britain the stones are called logging stones) It is also thought the word may have a link with Danish ‘logre’, to wag the tail, which could suggest a Norse origin. Others have suggested that the name may come from a Cornish use of the verb ‘to log’, used to describe the rocking action of a drunken man.
The coordinates given are for the well-known rocking stone in woodland at HUELGOAT in Brittany, Northwest France. This granite stone, called La Roche Tremblante, (the trembling rock) is larger than a family car and a single person can rock it if they know the exact spot on which to push. Local children often watch visitors trying to rock the stone and, when they give up, will divulge the secret for a few cents. The secret spot is also shown in one of the photographs below.
This Logan stone, although initially formed by erosion, like the many other huge boulders that litter this area, was probably deposited by water action. Local legend tells us that Gargantua, a good giant (written about by Rabelais), took his revenge on the inhabitants of Huelgoat who had served him a terrible meal by throwing enormous rocks smoothed by the sea from the coast of Finistère
To log this EarthCache you must photograph (yourself or your GPSr with) the Logan stone, then you must estimate the approximate size of ‘La Roche Tremblante’,
A) Its length (in metres)
B) Its height (in metres)
C) Its width (in metres)
Then, by multiplying these three figures together, calculate:-
D) Its volume (in cubic metres)
E) Finally, given that one cubic metre of granite weighs about 2.75 tonnes, calculate the approximate weight of the stone to the nearest tonne (ans +/- 30 tonnes accepted)
Email your answers A-E to me using this link or via the profile. When you receive a confirmatory reply you may log the cache and include your photograph with the log.
New EarthCache guidelines 2010
Under the new guidelines, a photograph can be requested but specific detail cannot be required. Consequently your photograph can be just a general photo of the site. However a personal touch such as your GPSr (or yourself/member of your team!) in the photo makes it much more interesting.
Please log the cache and include your photograph after receiving an email confirming your answers. (Unconfirmed logs will be deleted)
A final word of warning - it is said that if a woman touches a logan stone nine times at midnight, she will become a witch!!!
Pour valider cette EarthCache vous devez photographie (vous-même ou votre GPSr avec) ‘La Roche Tremblante’, alors vous devez estimer la taille approximative du `La Roche Tremblante',
A) Sa longueur (mètres)
B) sa taille (mètres)
C) sa largeur (mètres)
puis, en multipliant ces trois figures ensemble, calculez :-
D) Son volume (mètres cubes)
E) en conclusion, étant donné qu'un mètre cube de granit pèse environ 2.75 tonnes, calculez le poids approximatif de la pierre à la tonne la plus proche (La réponse a accepté +/- 30 tonnes) d'email admis vos réponses A-E à moi ici ou par l'intermédiaire du profil.
Quand vous recevez une réponse confirmatoire vous pouvez noter cette EarthCache et inclure votre photographie avec la notation.
Un mot final de l'avertissement - on lui dit que si une femme touche une pierre "Logan" neuf fois à minuit, elle deviendra une sorcière !!!
[EarthCaches. Leave nothing, take only measurements, pictures and memories!]
- ChaosSome of the other giant weathered boulders nearby.
- Logan StoneMeasurements required.
- Secret spotThis is the area in which to push upwards to get the stone to rock.
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Coordinates are in the WGS84 datum