geysers

A geyser is a spring that intermittently ejects a column of hot water and steam into the air. Geysers require a heat source, usually a shallow magma chamber, a supply of water, and an underground plumbing system with constrictions that trap and meter the flow. The eruption begins when water at depth is heated beyond its boiling point as pressure allows; when steam forms and expands in a constricted conduit, it forces the surrounding water upward, creating a venting column.

After an eruption, the geyser's conduit fills again with cooler water, and the cycle repeats. The interval, height, and duration depend on the geometry of the underground channels, the water supply, and the heat input. True geysers, as opposed to hot springs or fumaroles, erupt irregularly but with regular cycles; some are highly predictable, others highly variable.

Geysers are most common in tectonically active regions where heat from magma is near the surface, such as Yellowstone in the United States, Iceland's Haukadalur valley (home to Strokkur and the historic Geysir), New Zealand's Taupo Volcanic Zone, and parts of Italy, Russia, and Chile. The term geyser comes from Icelandic Geysir, from which it was adopted into other languages.

Geysers are sensitive to changes in groundwater, seismic activity, and climate. They attract tourism and are studied for geothermal energy potential and for insights into underground hydrothermal systems. Eruptions can be dangerous due to scalding water and steam, and many geysers are protected within national parks or reserves.