Malvizza mud volcanoes
The Malvizza mud volcanoes are the largest array of mud volcanoes in the southern Apennines of Italy. The phenomenon is purely sedimentary in nature, in contrast to volcanic phenomena like mofettas, fumaroles, and solfataras. The Malvizza mud volcanoes show some affinities with the salse of the central-northern Apennines and with the maccalube of Sicily.
Location and description
The Malvizza mud volcanoes are located in the Campania Apennines, in the municipal territory of Montecalvo Irpino, along a plateau of the Miscano valley at an altitude of above sea level. They are characterized by the emission of gaseous hydrocarbons—primarily methane, which at most sites accounts for more than 90% of emissions—as well as a continuous flow of weakly alkaline water at a temperature of. The solid component of the mud is composed of more than 95% illitic clay, with only traces of calcite and quartz. The deep layers of the subsoil of the Malvizza mud volcanoes are primarily scaly clays, alternating with regular layers of brecciole and nummulitic limestone.The volcanoes are located along the provincial road that leads from the state road 90 bis to Castelfranco in Miscano. The existence of an additional single mud volcano is attested on the opposite side of the Miscano valley, about 5 km from the site of the Malvizza mud volcanoes. It is located along the Fràscino arm, south of the Miscano river, and at an altitude of above sea level.
Cause
The mud volcanoes are caused by the presence of deep deposits of gaseous hydrocarbons which, in response to the compressive tectonic stresses typical of the Apennines-Adriatic area, tend to rise towards the surface. This produces bubbling in the spring waters they infiltrate.Due to extensive liquid emissions, the volcanoes' surface structures are short in height, even during droughts. They are sometimes nearly flat due to rainwater erosion, which enlarges the affected area and inhibits the development of vegetation.
The presence of methane and other flammable gases in the subsoil is well-known in the Miscano valley. In 1867, a firedamp spill and its subsequent explosion caused the death of an entire team of workers during the construction of the Cristina railway tunnel near the station at Castelfranco in Miscano, along the Naples-Foggia line. This incident occurred almost halfway between the Fràscino branch and the Malvizza mud volcanoes.