“As the gasses erupt from 3000 meters-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 dries off at the surface, creating a relatively solid conical structure,
resembling a real volcano. The mud expelled by them is cold,
as it comes from inside the Earth's continental crust layers,
and not from the mantle.”
Mud Volcanoes