Volca-pot Jeudi 12 mars à 14h00 en salle JJ.
Simone Jordan nous propose une présentation intitulée :
“Small volcanoes being big”
Basaltic, monogenetic volcanoes are commonly considered to be formed during small, single, short lived eruptions that affect only a small area surrounding the eruption point. Scoria and tuff cones, maars, and small shield volcanoes are produced by this type of eruptive activity, with scoria cones being the most common volcanoes on Earth. In the last decade, detailed research on monogenetic volcanoes has revealed complex eruptive histories of many monogenetic volcanoes and that some of these small volcanoes were produced during relatively big eruptions. The processes that control the formation and the size of the monogenetic eruption are still not well known, but their understanding is crucial for hazard assessment and civil protection, as many of the monogenetic fields are located in the vicinity of densely populated areas.
The eruption of the La Vache and Lassolas cones in the Chaîne des Puys is one of these relatively big eruptions, forming two scoria cones, a tephra deposit covering 26 km2, and a 22 km long lava flow. This study is unravelling the complicated eruption history of these two volcanoes and discovering various changes in the eruption dynamics ranging from sub-plinian and violent strombolian to quiet lava effusion. The high explosivity of this eruption demonstrates the importance of studies of monogenetic volcanoes with regard to possible threads of these volcanoes to the population living in their surroundings.