Volcanic cone

The cones , like Puy of Lemptégy, are generated by Magma S fluids. They are called volcanos of standard Strombolian. And they are represented the most by far in the Chaîne of Puys. From the mouth of the volcano, gas escapes from the magma by successive explosions which project each time of a few ten to more than 100 meters heights, of the incandescent fragments of still pasty lava. While whirling, certain blocks take an aerodynamic form: they are the volcanic bombs. The traditional volcanic cone is built projections which were amoncelées around the crater. It consists of movable slags and not completely of lava like the domes. The cones reach in general from 100 to 300 meters height. The crater generally is rounded, filled partially by projections of the close cones. At the end of the eruption, when the magma lost much gas, the lava which is not projected any more runs out. It cuts through a path through slags of the base of the cone, leaving intact the building, or by notching it, as for the Puys of the Cow or Lassolas. When the lava returns in contact with the colder air, it is covered with an almost solid crust which when casting advances, breaks in angular blocks. They pile up in disorder, and forms a chaotic surface which one calls of the cheires. The cheire of the Puy of Like is spread out over 8 km, while that of Puy of the Cow, impressive, is spread out over 14 km, causing the natural stoppings of the lakes Aydat and Cassière.

Sources

Extracts from a report of a pupil. Information is based on the Chaîne of Puys of the volcanos of Auvergne.

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