Mud Vulcanetti: The Bolle della Malvizza (literally "springs of the blackbird", in the Irpinia dialect, are located in the Campania Apennines, in the territory of Montecalvo Irpino, along a plateau of the Miscano valley at an altitude of 518 m asl. are characterized by the emission of gaseous hydrocarbons (methane for more than 90% [