Geothermal features can be observed in areas of active volcanism, or areas that have inactive volcanoes. Subsurface magma heats groundwater, creating steam and hot water. The hot, less dense water rises through fissures and cracks in the ground. When it reaches the surface, features such as geysers, fumaroles, hot springs, and mud pits are created.

Geysers are the most well known geothermal feature. Scientists do not completely understand how geysers work. They think that large amounts of groundwater fill underground cavities. The water in these is heated by nearby magma. Suddenly, some of the water flashes into steam, and the rest is forced violently from