Steam on its release, in geothermal wells.
I'm not sure what you mean by "caverns".
Natural caves don't normally act like that - except when glacial melt-water enters a hot lava-tube, or an island-arc volcano's magma chamber collapses and allows the sea in. That may be the cause of the tremendous explosion that ended a series of eruptions of Mt. Krakatau in 18(86?).
It is the groundwater that is heated or made cold and comes out of the spring. The groundwater is coming out of the spring.
artesian well
A Geyser can develop. It can also be a source of energy, i.e. Hydrothermal Energy.
This is known as a hot spring. This process is one source of geothermal energy.
Hot Springs, or a Geyser.
Caves
It is the groundwater that is heated or made cold and comes out of the spring. The groundwater is coming out of the spring.
artesian well
Geysers are, in fact, formed when groundwater is heated by nearby magma. They can also be formed by volcanic eruptions and earthquakes occasionally as well.
A Geyser can develop. It can also be a source of energy, i.e. Hydrothermal Energy.
geothermal energy
In volcanic areas the heated water is a source of escape for the volcanic gases. Water heated by magma gets very hot and needs to have a place to go or the ground will explode.
Hot springs or geysers are created when groundwater gets heated by hot intrusive rocks and can ascend via fractures in the crust. In the most extreme case so called phreatomagmatic eruptions take place. When magma ascends and reaches groundwater at shallow depths, the resulting steam expands dramatically and fractures the overlying rock thus producing a conical hole in the ground. These volcanic craters are referred to as maars.
True
A heated liquid become a gas at the boiling point.
This is known as a hot spring. This process is one source of geothermal energy.
When heated to its boiling point.