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Venturing to climb the boulders of chaos in the sidobre, Tarn, is not always easy ...

"Rivers or chaos
Along steep slopes, water rapidly leads sands and clays formed by the "decay" of granite. The balls formed of more resistant granite, remain in place and form amazing chaos called "rivers". Sometimes balls embedded in the catchment are released by rainwater and can accumulate in the chaos. There are as many forms of chaos that chaos. "

"... There are about 300 million years ago, magma molten rock cooled slowly beneath the surface of the earth to give birth to this crystalline rock. Granite in the basement, the massif sidobre cracked. water gets inside and persistent humidity transforms mica and feldspars in clay minerals.
Granite then disintegrates into a coarse sand. Cracks between the blocks get larger, the edges are rounded blocks. Runoff causes the elements of the arena, balls of fresh rock, landscape features Sidobre degrading gradually. Granite is a rock composed of Mica (black), feldspar (white) and quartz (gray).

First, we must say that the granite has nothing to do with lava that would have flowed from a volcano. Granite is cooled to depths of several kilometers.
Sidobre is a plateau (average altitude of 650m), granite about 120 km2 (15 km long and 8 km wide) which was formed at the end of the formation of the Hercynian chain, which only exists today the Massif Central.
The Massif du sidobre is what is known in geology granite pluton: plutonic rocks form much thicker than the lava puddles, and thus remain buried several kilometers from the Earth's surface.
This magma nat between 20 and 30 km deep, at a temperature of 600-800 degrees.
He intrudes Cambrian shales (older, about 530 million years) and migrated upward and remained several miles without reaching the surface.
For twenty million years, there has been an erosion of coverage shale.
Rainwater penetrating the granitic basement and moving along the horizontal and vertical fractures (joints) has defined these angular blocks of varying size. By infiltrating, water causing disintegration of the main minerals of granite by hydrolysis (chemical reaction which results in the processing of mineral rock by water).
During the service, a period dominated by a hot and humid tropical climate, the rock loses its cohesion, it disintegrates and is evolving into a material with the consistency of coarse sand, clay, more or less, the granitic sand. There is talk of arenization.
By staying above the bedrock, granitic arenas that hold water like a sponge allow the arenization progress down, sooner or later.
Smaller blocks are completely decomposed, the most important is round.
In the valley, flowing waters are clearing the granitic and give off a chaotic stack of blocks and balls. Sometimes two of them are in the balance one another.

Sidobre is one of the most important European extraction granite poles. Blocks are shipped to Italy, Spain, Germany, Belgium ...

On this exceptional and unique territory in Europe, the delights of amazing scenery, rocky water trembling or chaos that often have a name and a story .. "http://sidobre.tourisme-tarn.com/

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Additional Photos by Magaly PAGANO (Giustiniani) Gold Star Critiquer/Gold Note Writer [C: 193 W: 9 N: 391] (3242)
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