Minor Forms of Extrusive Volcanic Activity

Geysers and Hot Springs :- Even in areas where vulcanism does not generate active volcanies, water heated at depth in the crust by magma chambers can periodically escape as steam and hot water. A geyser is an intermittent turbulent discharge of superheated water ejected and accompanied by a vapour phase. Where hot water on its way upwards mixes with muds near the surface, a bubbling, boiling mud volcano may form. In some places hot springs have become tourist attractions: in Pamukkale (Turkey), dissolved salts from the hot water are lard down in spectacular calcium carbonate deposits, though the area is not volcanically active (read past post on this here).
Geysers
- hot pressurised water, stored in rock cavities underground which increases pressure
- normally find a small mound surrounding a pool of water. The water is very mineral enriched and when it 'splatters' minerals are deposited, forming the mound.
- pools are incredibly colourful due to dissolved minerals
- periodically form a fountain
i.e Old Faithful (Yellowstone National Park), Geysir (Iceland), New Zealand
RISKS - hot water and sulphurous gases
BENEFITS - tourism and geothermal energy exploitation oppurtunities

Hot Springs
- pool of warm geothermally heated water
- less pressurised water, hence no fountains
- water laden with minerals
i.e Japan, BlueLagoon (Iceland - technically a manmade version)
RISKS - very hot water
BENEFITS - tourism and social
Fumaroles:- Fumaroles are ares where superheated water turns to steam as it condenses on the surface. Personally, I think they look most spectacular when they form in ice, like those on Mount Erebus (this a film review but also contains a description of such fumaroles)

Fumaroles
- superheated water turns to steam, rises and deposits minerals to form chimney-like structures
i.e Stromboli, Erebus
RISKS - hot steam and sulphorous gases
BENEFITS - tourism and mineral extraction

Mudpots
- water geothermally heated, interacts and mixes with mud and surface deposits
i.e Vulcano
RISKS - slightly radioactive and very hot
BENEFITS - tourism