Shih (1967) classified mud volcanoes can be by the type of cone and size of the vent.
Type A – the cone has sides >200 and vent of a few dozen cm. e.g. Digity and Cascadoux
Type B – the cone has sides 5-200 and vent of a few dozen cm.
Type C – the cone has sides <50 and vent between 1-2m.
Type D– shaped like a caldera and vent of several meters across
Type O – small mud hole and vent of a few cm.