geisers

A geyser is a spring that intermittently erupts, ejecting jets of steam and hot water into the air. The term geyser comes from the Icelandic Geysir, named after the geothermal area in Haukadalur; the word itself derives from the verb geysa, meaning "to gush." Geysers form in volcanic regions where heat from magma warms groundwater and where underground plumbing allows pressure to build.

In a typical geyser, an underground chamber or complex of channels stores hot water beneath a constriction. As water near boiling temperatures rises and becomes steam, pressure increases until the overlying water column can no longer be contained, causing a rupture that drives a sudden eruption. The eruption releases steam and superheated water that can spout for seconds to minutes, sometimes meters high. Afterward, the system recharges with cold water, and the cycle repeats.

Geysers are relatively rare and concentrated in areas with recent volcanic activity and abundant groundwater. The most famous geysers occur in Yellowstone National Park in the United States; others are found in Iceland, the Taupo Volcanic Zone in New Zealand, Kamchatka in Russia, and certain parts of Italy and Chile. Geyser activity is sensitive to changes in recharge, seismic disturbances, and human activities such as groundwater pumping.

Two common forms are cone-bearing geysers, which eject through a siliceous or carbonate cone, and fountain-type geysers, which erupt from a broad pool without a constructed cone. The deposits around a geyser, often silica sinter, can build intricate chambers and terraces over time.