Malvizza Bubbles, Mud volcano field in Montecalvo Irpino, Italy.

The Malvizza Bubbles are the largest array of mud volcanoes in the southern Apennines, located on a plateau in the Miscano valley at 518 m above sea level. They consist of numerous low, bubbling cones that emit methane (over 90% of the gas), weakly alkaline water (pH 8) at 18 °C, and illitic clay mud. Rainwater erosion sometimes flattens the cones and expands the muddy area.

In 1867 a firedamp spill and explosion, set off by torches used for lighting, killed an entire team of workers building the Cristina railway tunnel on the Naples-Foggia line near Castelfranco in Miscano, almost halfway between the Fràscino branch and the Malvizza mud volcanoes. The site has since been studied for possible natural gas exploitation, its methane contribution to the greenhouse effect, and radon anomalies as possible seismic precursors.

The name malvizza comes from the Irpinia dialect word for a bird. In early 2005 researchers isolated a new gram-positive bacterium, Alkalicoccus saliphilus, from the green algae of the bubbling pools; it shows 99.9% affinity with a strain from a soda lake in Inner Mongolia and over 97% with two strains from Kenya's Rift Valley.

The site lies along the provincial road from state road 90 bis to Castelfranco in Miscano, in the Miscano valley plateau at 518 m. The mud vents are low and sometimes nearly flat after rain, so the ground is muddy and slippery; waterproof footwear helps. Rain increases the flow and suppresses vegetation, so the pools are most visible after wet weather.

In 2005 a new bacterium, Alkalicoccus saliphilus, was isolated from the green algae of the bubbles; it is 99.9% similar to a strain from a soda lake in Inner Mongolia and over 97% to two strains from Kenya's Rift Valley. A single separate mud volcano lies about 5 km away on the far side of the Miscano valley, at 400 m.