Chaîne des Puys, Chastreix, Clermont-Ferrand, France

For lack of active beings, these familiar reliefs are indeed living volcanoes. Their last eruption goes back less than 7000 years and, over the course of their history, the puys have experienced much longer periods of sleep than they currently have. Finally, the course of geological time is such that no doubt two volcanoes never erupted simultaneously.

To stick to the forms, the chain of Puys, which aligns some 80 volcanoes, begins in the north with the Gour de Tazenat , typical of the circular lakes of which Auvergne is prodigal. This is the signature of a rather ordinary – but very violent – volcanic phenomenon, which occurs when a rise of magma comes into contact with a water table. Water and fire do not mix well and the cataclysmic explosion that follows cuts the ground like a cookie cutter, leaving a deep crater called maar, surrounded by a ring of debris. The depression thus created only asks to retain the water, as it also happened at Pavin Lake, during the last Auvergne eruption.

In the large family of craters, the most common buildings are of Strombolian type: like their Italian model, these conical and weakly dangerous volcanoes are built by spitting slag and releasing lava flows near their base. They are distinguished by their simple crater, such as the puzzles of Jumes and Ghouls; their craters interlocked, like the puys of Pariou and Como ; or by their crater ripe, lava flows having been powerful enough to carry slag as on a treadmill, such as twin puys Cow and Lassolas.