Geysers

Amanda Lloyd

These are hot springs characterised by periodic turbulent ejections of water accompanied by water vapour (Park, 2001). The word geyser comes from Geysir an Icelandic spring at Haukadalur, which in turn comes from the Icelandic verb Gjósa meaning to gush (Neohumanism, 2004). They are temporary features, last only a few thousand years, and are mainly associated with volcanic areas (Geology, 2009). The formation of geysers is due to very particular hydrogeological conditions so they are very rare in occurrence. About 1000 geysers are known worldwide and around 50% of these are found in Yellowstone National Park alone (Geology, 2009).

Groundwater permeates to a depth of around 2000m where it comes into contact with hot rocks heated by the magma chamber of the nearby volcano. A reservoir is

required to hold the water whilst it is heated to allow and store the build-up of pressure. The water at the base of this reservoir begins to boil and the resultant steam bubbles rise to the surface of the pipe. The water at the top is cooler and therefore pushes down on the underlying water adding to the pressure (Glennon, 2008). When the rising bubbles finally break through the surface of the vent, the built up pressure is released and an eruption occurs, like popping a champagne bottle. Eventually the water in the pipe cools enough, or there is a significant reduction in pressure so the eruption stops and the process repeats itself (Strom, 1995). The refilling of the pipe can vary in time from a few seconds to several days depending on the size of the geyser (Glennon, 2008).

Most geysers form in areas where volcanic rhyolite is the dominant rock type. This can dissolve in hot water and forms deposits called siliceous sinter, or geyserite, along the inside of the pipes (NPS, 2008). Overtime these build up and cement the rock tighter together, strengthening the walls of the pipe prolonging its life. However, they are easily destroyed by people throwing litter into them and by de-watering from geothermal power stations. This reduces the amount of water available to the geyser as well as reducing the pressure preventing an eruption from occurring.

In some geothermally active areas, artificial geysers have been built by drilling into the ground and fitting an impermeable casement around the hole to store the pressure. In these cases the vents are artificial but to work they have to be tapped into natural hydrothermal systems. These are known as artificial geysers and are technically known as erupting geothermal wells (Neohumanism, 2004).

The largest geyser is Steamboat geyser in Yellowstone National Park that ejects water 250 – 390ft into the air (Jones, 2006). The largest used to be Waimangu in New Zealand which ejected water 600-1000ft in the air. It formed in 1888 by a volcanic eruption and started erupting in 1900 but it was destroyed 4 years later by a landslide in 1904 (Jones, 2006).

References

Geology. 2009. http://geology.com/articles/geyser.shtml. Accessed on 10/04/09
Glennon, A. http://www.uweb.ucsb.edu/~glennon/geysers/. 2008. Accessed on 10/04/09
Jones, G. L. 2006. http://www.wyojones.com/tall.htm. Accessed on 19/04/09
2004. http://neohumanism.org/g/ge/geyser.html. Accessed on 09/04/09
NPS. 2008. http://www.nps.gov/archive/yell/insideyellowstone/glossary.htm. Accessed on 10/04/09
Park, C. C. 2001. The Environment: principles and applications. Routledge publishing
Strom, K. M. 1995. http://www.hanksville.org/daniel/geology/geysers.html. Accessed on 11/04/09

This short summary about geysers was written by Amanda Lloyd, a second year undergraduate studying geography and geology at the University of Manchester, in May 2009. Our thanks to her for allowing permission to publish it here.