Geothermal Features - Mud Pots


Mud bubbling and popping Thick Mudpot Typical Mudpot
Mudpots Red Spouter

One of the most interesting looking features of a thermal area is mudpots. The source of mud pots is again an underground chamber of water. The difference is the geology of the surrounding rocks - these rocks are "soft", that is, easily broken down or dissolved. Other requirements for mudpots to occur are, limited availability of water, and the presence of hydrogen sulphide. In this case, hydrogen sulphide reacts with water forming sulphuric acid. The acid water slowly corrodes into the rocks and dissolves them, forming fine particles of silica and clay. This viscous clay-water mixture creates a marshy or muddy area, with the hot mud boiling and bubbling out, erupting at the surface. Such formations are called mud pots. They vary in consistency from very soapy to almost hard-baked mud.

The mud could be black, white and all shades of grey in between. There are some coloured mud pots, also known as paint pots, which range from pink to bright red to purple, due to the iron oxides, potassium, and magnesium in the soil. The reason for these coloured paint pots is a lack of sulphur: because if sulphur were present, it would react with the iron oxides forming pyrite, which is a grey mineral.

Watch this mud pot in action (Kamchatka, Russia):
Bubbling mud pots (Yellowstone National Park, USA):

Mud pots are known to be as much as 20m (65 ft) across in some cases. There is usually a lingering smell of rotten eggs from the hydrogen sulphide. Mud pots make interesting sounds as various gases bubble through the thick clay mud making it bubble and plop. If the bubbling mud is very viscous, big intact blobs of it are thrown out, forming a little mound, generating a mud volcano. The mud volcano develops a little opening at the top, through which steam escapes.

Mud Bubbles

Spectacular shapes and ripples form within mud pots, depending on the consistency of the mud. These formations vary seasonally too: in summer when the mud is thick and drying, small volcanoes build up. But in the wet winters, the mud is thinner. When the thin mud explodes sporadically, it leaves fantastic abstract shapes, which it is fun to interpret as flowers, knobs, a human face, concentric rings, etc.