Overblog
Editer l'article Suivre ce blog Administration + Créer mon blog

Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #"Readers' Words"

Near Issoire, the village of Usson is built on an old basalt peak, which culminates at 639 meters.

This surprising geological formation is linked to a phreatomagmatic eruption, resulting from the contact of lava with water. The region was then a vast lacustrine zone, in which the magma made its way.

This volcanism began 25 Ma ago, and is older than the volcanic events that gave rise to the volcanoes of Cantal, Mont-Dore or those of the chaîne des Puys .

The volcanic organs of Usson - photos © J-M M. - one click to enlarge
The volcanic organs of Usson - photos © J-M M. - one click to enlarge

The volcanic organs of Usson - photos © J-M M. - one click to enlarge

The organs of Usson - "Prisms for building" - explanatory panel - photo © J-M M. - one click to enlarge

The organs of Usson - "Prisms for building" - explanatory panel - photo © J-M M. - one click to enlarge

The organs, located south of the village, are the remains of the deep part, the chimney of an old volcano which has now disappeared under the effect of erosion. Usson's vertical organs are cooled from above, not from the sides of the chimney. The regularity of the prisms is also associated with a rather slow cooling.

 

The village, classified among the most beautiful villages in France, was built thanks to the hexagonal prisms, and the arkose, visible in the walls of the church of St Maurice.

The Castle of Usson, demolished on the order of Cardinal de Richelieu, had previously been, from 1585 to 1605, the place of house arrest of Marguerite de Valois (1553-1615), nicknamed by Alexandre Dumas Queen Margot, first wife (1572-1599) of King Henry IV of France.

The volcanic organs of Usson - photo © J-M M. - one click to enlarge

The volcanic organs of Usson - photo © J-M M. - one click to enlarge

The Saint Maurice church on the hill of Usson - photo © J-M M.

The Saint Maurice church on the hill of Usson - photo © J-M M.

"Prisms for building" - a basalt wall - photo © J-M M. - one click to enlarge

"Prisms for building" - a basalt wall - photo © J-M M. - one click to enlarge

The Château du Sailhant, in the commune of Andelat, was built in the 13th century on a triangular basalt spur, about 20 to 25 meters high.

It is also known for the presence of the Sailhant (or Babory) waterfall nearby.

 The Babory stream flows from a height of about twenty meters at this point into a chasm whose depth is estimated between 6 and 7 meters.

Sailhant castle - photo © J-M M. - one click to enlarge

Sailhant castle - photo © J-M M. - one click to enlarge

Sailhant or Babory waterfall - photos © J-M M. - one click to enlarge
Sailhant or Babory waterfall - photos © J-M M. - one click to enlarge

Sailhant or Babory waterfall - photos © J-M M. - one click to enlarge

Sources:
- Futura - The Exploratorium: the organs of Usson in the land of volcanoes.
- Sailhant castle - wikipedia

Commenter cet article

Archives

Articles récents

Hébergé par Overblog