<Tr> <Td_colspan="2"> Strokkur geyser, Iceland </Td> </Tr> <Tr> <Th> Formed by </Th> <Td> Particular hydrogeological conditions that exist in a few places on Earth </Td> </Tr> <P> A geyser (/ ˈɡaɪzər /, also / ˈɡiːzə /) is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by steam . As a fairly rare phenomenon, the formation of geysers is due to particular hydrogeological conditions that exist only in a few places on Earth . Generally all geyser field sites are located near active volcanic areas, and the geyser effect is due to the proximity of magma . Generally, surface water works its way down to an average depth of around 2,000 metres (6,600 ft) where it contacts hot rocks . The resultant boiling of the pressurized water results in the geyser effect of hot water and steam spraying out of the geyser's surface vent (a hydrothermal explosion). </P> <P> A geyser's eruptive activity may change or cease due to ongoing mineral deposition within the geyser plumbing, exchange of functions with nearby hot springs, earthquake influences, and human intervention . Like many other natural phenomena, geysers are not unique to planet Earth . Jet - like eruptions, often referred to as cryogeysers, have been observed on several of the moons of the outer solar system . Due to the low ambient pressures, these eruptions consist of vapor without liquid; they are made more easily visible by particles of dust and ice carried aloft by the gas . Water vapor 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 the latter two cases, instead of being driven by geothermal energy, the eruptions seem to rely on solar heating via a solid - state greenhouse effect . </P>

Intermittent hot spring that erupts jets of hot water and steam