The volcanic activity of Coiron has developed at the level of two types of buildings: Strombolian volcanoes and explosion craters called maars. The volcanic plateau of Coiron is an ancient massif since the lavas have been dated between 6 and 8 million years approximately. Strombolian cones have been seriously damaged by erosion. Some have been completely destroyed and today we can only observe the lower part of the chimney, in the form of large lava pellets, the necks (Sceautres, Roche Chérie...), or veins sometimes a kilometer long , the dykes. The basalt flows have a particular structure due to their cooling: the lower part is cut into prisms or organs.