Geyser

Definition of Geyser     

     A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase (steam). The formation of geysers is due to particular hydrogeological conditions, which exist in only a few places on Earth, so they are a fairly rare phenomenon. 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).

Beehive Geyser

Form of Geyser

     Geysers are temporary geological features. Geysers are generally associated with volcanic areas. As the water boils, the resulting pressure forces a superheated column of steam and water to the surface through the geyser's internal plumbing. The formation of geysers specifically requires the combination of three geologic conditions that are usually found in volcanic terrain.

1. Intense Heat : The heat needed for geyser formation comes from magma that needs to be near the surface of the earth. The fact that geysers need heat much higher than normally found near the earth's surface is the reason they are associated with volcanoes or volcanic areas. The pressures encountered at the areas where the water is heated makes the boiling point of the water much higher than at normal atmospheric pressures.
2. Water : The water that is ejected from a geyser must travel underground through deep, pressurized fissures in the Earth's crust.
3. Plumbing System : In order for the heated water to form a geyser, a plumbing system is required. This includes a reservoir to hold the water while it is being heated. Geysers are generally aligned along faults.The plumbing system is made up of a system of fractures, fissures, porous spaces and sometimes cavities. Constrictions in the system are essential to the building up of pressure before an eruption.

Eruption of Geyser

     Geyser activity, like all hot spring activity, is caused by surface water gradually seeping down through the ground until it meets rock heated by magma. The geothermally heated water then rises back toward the surface by convection through porous and fractured rocks. Geysers differ from non-eruptive hot springs in their subterranean structure; many consist of a small vent at the surface connected to one or more narrow tubes that lead to underground reservoirs of water and pressure tight rock.

1. Steam rises from heated water

2. Pulses of water swell upward

3. Surface is broken

4. Ejected water spouts upward and
 falls back down into the pipe

Type of Geyser

     There are two types of geysers: fountain geysers which erupt from pools of water, typically in a series of intense, even violent, bursts; and cone geysers which erupt from cones or mounds of siliceous sinter (also known as geyserite), usually in steady jets that last anywhere from a few seconds to several minutes. Old Faithful, perhaps the best-known geyser at Yellowstone National Park, is an example of a cone geyser. Grand Geyser, the tallest predictable geyser on earth, (although Geysir in Iceland is taller, it is not predictable), also at Yellowstone National Park, is an example of a fountain geyser.

Fountain Geyser (erupting from the pool)

Cone Geyser
(Old Faithful Geyser in Yellowstone National Park)