Extrusive Landforms


  • A geyser is a rare kind of hot spring that is under pressure and when it erupts it sends jets of water and steam into the air.
  • They are a tube-like hole in the ground that runs deep into the crust in which they are filled with water. Water in the lower part of the tube becomes superhot and begins to turn into steam or gas then it sends steam jets towards the surface.



  • A fumarole is an opening in a planet’s crust, often in the neighbourhood of volcanoes, which emits steam and gases such as carbon dioxide, sulphur dioxide, hydrochloric acid, and hydrogen sulphide.
  • The steam is created when superheated water turns to steam as its pressure drops when it emerges from the ground.
  • Fumaroles are often present on active volcanoes during periods of relative quiet between eruptions.
  • Fumaroles are closely related to hot springs and geysers. In areas where the water table rises near the surface, fumaroles can become hot springs.


Boiling Mud

  • Sometimes there is groundwater below the ground deposit which is heated below but doesn’t explode.
  • When the water mixes with the surface deposits, boiling mud is formed. These features are very common in Iceland.
  • A hot spring is basically heated groundwater, which is geothermal heating by the magma below. It then mixes with the surface deposits and can form muddy water.




  • A Solfatara is a volcanic steam vent in a shallow volcanic crater; it is a dormant volcano, which still emits jets of steam with sulphurous fumes for example the Bay of Naples in Italy. A volcanic area that gives off sulphurous gases and steam.