Lots of mud volcanoes in Gobustan, Azerbaijan.

A mud volcano or mud dome is a kind of volcano that is made by liquids and gases from the earth. There are many different ways that mud volcanoes can be made. Temperatures in a mud volcano are much cooler than that of a regular volcano. The biggest mud volcanoes are 10 kilometers in diameter and can be as tall as 700 meters. Most of the gases given off by mud volcanoes are methane. Other gases given off include carbon dioxide and methane. They usually spit out liquids with solids in the liquids. An example of this would be water with salt or acids in the water.