mud volcanoes

The Muddy Volcanoes in Buzau county are not the volcanoes you would expect. They're not the big, real volcanoes that scare off people and clog the European airspace with volcanic ash. Not by far. But they're a pretty amazing place, hidden somewhere in the Buzau mountains.
The Muddy Volcanoes were formed from the gas which comes from 30,000 meters underground. The gas goes through a clay sector, then through the underground water. So the gas pushes the water and the clay to the surface (which by that time become mud), creating small cones which resemble the shape of a volcano.