Lemptégy

The Lemptégy is a Volcan of the Chaîne of Puys, deadened, like all the volcanos of Metropolitan France.

It is of effusive type, i.e. its Lave was fluid and could easily run out on the slopes. That formed a cone sunk Scorie S, of a black red color. In Lemptégy, this cone measures 120 Mètre S top. Slags of the cone were exploited: they are locally called Pouzzolane S. It is a rock which melts at very high temperature, very light since made up of multitudes of small cavities. They constitute an excellent heat insulator and are used they still today to manufacture Concrete block or to sand the roads. The color of these slags can give us interesting information.

Indeed, these slags including/understanding a little Fer oxidize during an exposure to a Température of 600 degrees Celsius during more than 6 hours. The slags located close to the heart of the volcano, more exposed to heat, have thus a red color to tend whereas those constituting the bottom of the cone are black, having cooled more quickly. In Lemptégy, red and black slags are intermingled since the volcano knew two successive castings, which one can very notice with the hole dug for the exploitation of Puy. One can observe at this place a kind of cross-section of the volcano and thus analyze the various layers. Lemptégy did not emit only slags but also bends S, of the kinds of large heaps of lava projected in the air. When these bombs present a form in beam, one can say that it were formed starting from a fluid block of lava which carried out a trajectory in gimlet; the bombs in the shape of “dung of cow”, as for them, were formed by a superposition of blocks of lava crushed on the ground and finally the bombs in “cabbage flower” were formed by blocks of lava mixed with Steam. These bombs consist of Basalte.

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