Geyser
A geyser is a hot spring with plumbing tight enough to let heat, water, and pressure build until water and steam burst upward.
What a geyser is
A geyser is a hot spring that erupts intermittently, sending hot water and steam above the ground. It is part of a hydrothermal system: water moves underground, absorbs heat from hot rock, and returns to the surface through cracks, tubes, and chambers.
Heat, water, and plumbing
Geysers need a strong heat source, usually in volcanic or recently volcanic terrain. Rain and snowmelt seep downward as groundwater, then warm as they circulate through hot rock. The unusual part is the plumbing: a reservoir and a narrow passage can trap water long enough for pressure to rise.
Why eruptions happen
Deep water can become hotter than the surface boiling point because the weight of water above it keeps pressure high. When some water escapes near the top of the system, pressure falls. More water then flashes into steam, expands rapidly, and pushes a mixture of steam and hot water through the vent.
Geysers, hot springs, and fumaroles
All geysers are hot springs, but most hot springs do not erupt. A steady hot spring has plumbing that lets heated water flow out without storing enough pressure for a burst. A fumarole is different again: it mainly vents steam and volcanic gases rather than a pulsing column of liquid water.
Minerals around the vent
Many geyser waters carry dissolved silica picked up underground. As hot water cools at the surface, silica can precipitate as sinter, also called geyserite. Over time it can build pale aprons, rims, cones, and terraces around vents and runoff channels.
Eruption patterns change
Some geysers erupt often enough to be forecast within a rough window; others pause for years or change after earthquakes, shifts in groundwater, mineral sealing, or human disturbance. A geyser is not a machine with a fixed timer. Its rhythm comes from a hidden, changing plumbing system.
Hazards and protection
Geyser basins are dangerous even when they look quiet. Thin crust can hide near-boiling water, and eruptions may throw scalding water without much warning. Boardwalks, closures, and monitoring protect visitors while also helping preserve fragile mineral deposits and microbial habitats.
Why it matters
Geysers are visible clues to underground heat, water circulation, mineral deposition, and volcanic history. They also help scientists study hydrothermal hazards and geothermal systems without drilling directly into the hottest parts of the crust.