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Minor Extrusive Features
Hot springs are a water flow that is produced by the
emergence of geothermally heated groundwater from the
Hot spring water often has high mineral content because hot
water holds a lot of dissolved solids.
Example: Blue Lagoon, Iceland
Geysers are hot springs that intermittently spout a column of hot water and
steam into the air.
Groundwater is heated to above boiling point by magma deep in the crust.
The hot water becomes pressurised and forces its way to the surface along
cracks in the rocks.
The hot water and steam spray up from a vent.
Example: Old Faithful, Yellowstone National Park
Fumaroles are areas where superheated water turns to steam as it
condenses on the surface.
These features are typical of areas such as Solfatara in Italy, where the
escape of steam and water mixed with sulphur-rich gases gives rise to the
collective name for these features of solfatara.
Example: Solfatara, Italy
A boiling mud pool is another type of hot spring.
They form in areas with very fine-grained soil.
The hot spring water mixes with the soil to create a hot muddy pool.
The pools sometime contain brightly-coloured mud because of minerals
deposited by the hot water.
Example: Yellowstone National Park, America