Mud volcanoes are an amazing and spectacular geologic phenomenon that can hit our fantasy with a particular touch.
They are built with mud by nature as small volcanoes generally of some meters high (they also can be smaller or even more rarely taller)
Their formation is due to the presence in the deep soil (hundreds-thousands of meters) of hydrocarbon reservoirs that are not well constrained under a low permeability cap.
The pressure permits the hydrocarbons (generally methane) and saltwater to go up in the ground until getting out on the ground, building a mud cone.
In the Northern Apennines (Norther Italy) they are well known as their presence is well documented in many localities, especially (but not only) in the Northern Apennines piedmont area in the Province of Modena and Bologna.
The pictures were taken in the "Salse di Nirano" park where a system of fences and pathways has been realized to can better preserve these strange and suggestive geologic forms.
The name Salse is the name locally used and it stands for the presence of "saltwater", while "Nirano" is the locality belonging to the municipality of Fiorano Modenese.
The images were taken by me with a 5Mpx simple photo camera.