Small volcano-shaped structures typically a few meters high caused by the eruption of mud and natural gases.
Berca Mud Volcanoes in Buzău County in Romania.
Photo credit: (c) Cristian NISTOR / AGERPRES ARCHIVE
'Scientist Grigore Cobalcescu explained the genesis of the mud volcanoes as the outcome of the combination of underground waters and natural gas, which by expanding to the surface dissolve rocks, turning them into a muddy paste. Once reaching the surface, the mixture creates some cone shapes, wherefrom the name volcanoes,' explains publicist Horia Baescu.
As the gases erupt from 3000 metres deep towards the surface, through the underground layers of clay and water, they push up underground salty water and mud, so that they overflow through the mouths of the volcanoes, while the gas emerges as bubbles. The mud expelled by them is cold, as it comes from inside the Earth's continental crust layers, and not from the mantle.
Photo credit: (c) Cristian NISTOR / AGERPRES ARCHIVE