Geyser
A rare spring that erupts intermittently with steam and water.
A geyser is a rare type of hot spring that erupts intermittently, shooting a turbulent mixture of hot water and steam into the air. This phenomenon requires a specific set of underground conditions, usually found only in volcanically active regions where magma sits close to the surface. Surface water seeps down roughly 2,000 meters until it meets hot rock, where it becomes pressurized and boils, forcing steam and water upward through a vent.
Geysers are not permanent features. Their activity can shift or stop entirely due to mineral deposits clogging their internal pipes, changes in nearby hot springs, earthquakes, or human interference. They are also not unique to Earth. On several moons in the outer Solar System, jet-like eruptions—called cryogeysers—have been spotted. Because the ambient pressure is so low, these eruptions release only vapor, not liquid, made visible by dust and ice particles. Enceladus, a moon of Saturn, has water vapor jets near its south pole, while Neptune’s moon Triton shows nitrogen eruptions. Mars may have carbon dioxide eruptions from its southern polar ice cap. The plumes on Enceladus are thought to be driven by internal heat, while those on Mars and Triton might result from solar heating through a solid-state greenhouse effect. None of these extraterrestrial examples have the subsurface water system that defines terrestrial geysers, setting them apart from features like fumaroles.
The word "geyser" entered English in the late 1700s, taken from Geysir, a specific Icelandic geyser whose name means "gusher."
Geologically, geysers require three conditions found in volcanic terrain: heat, water, and a plumbing system of fractures, fissures, and cavities that includes a reservoir. The heat comes from magma near the surface. As water heats and dissolves silica from rocks like rhyolite, it later cools near the surface, depositing amorphous opal that gradually turns into quartz, forming a coating called geyserite. This geyserite often covers microbial mats, which can make up half the volume of the deposit.
The eruption process begins when surface water seeps down to hot rock. Unlike non-eruptive hot springs, where heated water rises by convection, geysers have narrow constrictions in their plumbing that trap pressure. Cooler water at the top presses down on hotter water below, like a pressure cooker lid, allowing the lower water to become superheated. When boiling finally starts, steam bubbles rise and burst through the vent, splashing out water. This reduces the column’s weight and pressure, causing the superheated water to flash into steam and erupt violently. After the eruption, the remaining water cools, groundwater seeps back in, and the cycle repeats. Eruption duration and intervals vary widely: Strokkur in Iceland erupts for seconds every few minutes, while Grand Geyser in the United States erupts for up to ten minutes every eight to twelve hours.
Geysers fall into two general types. Fountain geysers erupt from pools in intense, often violent bursts. Cone geysers erupt from mounds of siliceous sinter in steady jets lasting seconds to minutes. Old Faithful in Yellowstone National Park is a cone geyser; Grand Geyser, the tallest predictable geyser on Earth (though Geysir in Iceland is taller but unpredictable), is a fountain geyser.
- type
- Geological feature
- first_known_use_of_term
- Late 18th century
- etymology
- From Geysir, a specific geyser in Iceland, meaning 'Gusher' in Icelandic
- key_conditions
- Heat, water, and a subsurface hydraulic system with the right geometry
- largest_geyser_field
- Yellowstone National Park, USA
- tallest_active_geyser
- Steamboat Geyser in Norris Geyser Basin
Lore & Background
Geysers are nonpermanent geological features generally associated with areas of recent magmatism. The pressurized water boils, and this causes the geyser effect of hot water and steam spraying out of the geyser's surface vent. The formation of geysers specifically requires the combination of three geologic conditions: heat, water, and a subsurface hydraulic system with the right geometry. Geysers have constrictions in their plumbing that create pressure build-up, differentiating them from non-eruptive hot springs. Geysers are fragile and may change or cease due to ongoing deposition of minerals within their plumbing, exchange of functions with nearby hot springs, earthquake influences, and human intervention. Many have been destroyed by people throwing debris into them, while others have ceased to erupt due to dewatering by geothermal power plants. The Geysir in Iceland has had periods of activity and dormancy; during its long dormant periods, eruptions were sometimes artificially induced by the addition of surfactant soaps. Geysers are not unique to Earth. Jet-like eruptions, often called cryogeysers, have been observed on several moons of the outer Solar System. Water vapour jets have been observed near the south pole of Saturn's moon Enceladus, while nitrogen eruptions have been observed on Neptune's moon Triton. There are also signs of carbon dioxide eruptions from the southern polar ice cap of Mars. In all three cases, there is no evidence of the subsurface hydrological system which differentiates terrestrial geysers from other sorts of venting.
Reader's Guide
Geysers are significant as rare natural phenomena that demonstrate the interaction of water, heat, and geological structure. They are primarily found in volcanic areas, with Yellowstone National Park containing half of the world's total number of geysers. The study of geysers has contributed to understanding hydrothermal systems and the conditions necessary for life in extreme environments. These organisms have heat-stable enzymes used in medicine and biotechnology, such as in manufacturing antibiotics, plastics, detergents, and fermentation products. The first discovered and most important for biotechnology is Thermus aquaticus. Geysers also provide insights into planetary geology, as similar venting phenomena occur on other celestial bodies, though without the subsurface hydrological system that defines terrestrial geysers. The fragility of geysers highlights the impact of human activity and environmental changes on geological features.
Did You Know?
- The term 'geyser' comes from Geysir, a specific geyser in Iceland, meaning 'Gusher' in Icelandic.
- Geysers have been observed on moons of the outer Solar System, including Enceladus and Triton.
- Some bacteria in geysers prefer temperatures higher than the boiling point of water.
- The tallest predictable geyser on Earth is Grand Geyser at Yellowstone National Park.
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