Editing Ardèche (section)

====Western mountains====
 
The mountains that border the western frontier of the department have an average altitude of 1,100 metres. They are of largely [[granite|granitic]] composition, split by the Velay [[Basalt]]s of the Massif of [[Mont Mézenc|Mézenc]], and the [[Forez mountains]], centred upon [[volcanoes|volcanic]] cones of ash, [[lava]] plugs and numerous [[magma]] flows (Mézenc: 1,754 metres; [[Mont Gerbier de Jonc|Gerbier de Jonc]]: 1,551 m). Their inclination slopes gently westward, leading to a westerly flow of water to the [[Atlantic]]. Here the [[Loire]] has its source. Within a few kilometres is the volcanic lake of Issarlès (92 ha, 5&nbsp;km in circumference, 108 m in depth). The climate is extreme: snow for many months, very violent winds in autumn and winter (known locally as "la [[burle]]"), frequent fogs in the valleys, extreme temperature changes between the seasons, with heavy rains (1,500&nbsp;mm per year in average) concentrated in September and October.