Geysers are rather amazing things: literal jets of hot, pressurised water that shoot from the ground, often dozens of metres into the air. To form these erupting hot springs, water has to travel through fissures to a depth of two kilometres below the surface and be warmed past the boiling point by a constant supply of volcanic magma lurking under the surface, causing an explosion of water that forces its way back to the surface via narrow cracks in the bedrock. Of the world’s 1 000 or so geysers, half are located in the confines of the United States’ Yellowstone National Park, but the actual term ‘geyser’ is derived from a single such spring in the volcanic hotbed of Iceland.
Distribution of the world’s geyser fields. Source: Worldtraveller, http://en.wikipedia.org/wiki/File:World_geyser_distribution.gif. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported licence.
Geysir eruption, 2000. Source: D. Schweitzer, http://commons.wikimedia.org/wiki/File:Erupting_geysir.jpg. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported licence.
Geysir (from the Icelandic geysa, ‘to gush’) was the first gushing hot spring sighted by Europeans and is known to have existed in its current form at least since 1294, when an earthquake forced the emergence of numerous hot springs in the Haukadalur region of western Iceland (to this day, numerous springs and geysers are present in the valley). The five separate layers of mineral deposition at the site, however, indicate that hot springs have existed at this location in one form or another for at least 10 000 years. The name ‘Geysir’ was taken from this location and applied by Europeans to other gushing hot springs around the world as they came across them. At its peak, Geysir regularly shot streams of water 50-70 m (165-230 ft) into the air.
Geysir eruption, 2009. Geysir is unusual in that it has an especially high level of radon, approximately 10 to 100 times that of most other Icelandic springs. Sources: A. Lederer, http://www.flickr.com/photos/ledr/3604291114/ and http://www.flickr.com/photos/ledr/3604265186/. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic licence.
The 2009 eruption from above. Note the rim of silica deposits surrounding the vent. Source: Chmee2, http://commons.wikimedia.org/wiki/File:Great_Geysir_(4).jpg. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported licence.
Unlike nearby geysers in the Haukadalur area such as the mammoth Strokkur (just 50 m/165 ft away), which projects anywhere from 15 to 40 m (50 to 130 ft) in height every 4 to 8 minutes, Geysir is rather inactive, often going years between eruptions. Dormant for much of the second half of the 19th century, it re-erupted in 1896 after an earthquake, beginning a 14-year-long period where it erupted once or twice each hour, only to fall to once every six hours by 1913 and go silent against three years later.
Geysir on a calmer day. Source: C. Peterson, http://www.flickr.com/photos/clarissa/23528218/. Licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic licence.
With no volcanic activity in the immediate area over the past 10 000 years, the various re-emergences of Geysir have in recent years largely been caused by earthquakes and human activity. Following the 1916 dormancy, Geysir temporarily roared back to life in 1935 when a ditch was dug through the silica that had accumulated around the vent, lowering the water table. Eventually, mineral deposition from the spring rebuilt the silica rim, and the geyser was silenced. For a period beginning in 1981, artificially reactivating Geysir has became a routine activity; the silica ditch was dug out again and large amounts of carbolic soap powder were placed inside the spring to provoke it into action to sate the visitors the spring receives each year on Icelandic National Day. Today, dumping soap into Geysir is prohibited. Along with neighbouring geysers, Geysir was rejuvenated again naturally for a couple of days in June 2000 after a small earthquake.
Geysir is now largely dormant, erupting occasionally a few times per year but hardly at the 50-70 m (165-230 ft) heights of old; current eruptions are more in the 8-10 m (26-33 ft) range, and it takes approximately 8-10 hours for the vent to refill with water after an eruption. Most tourists visiting the site looking for an eruption head to neighbouring Strokkur instead. The next earthquake will determine the next re-awakening of Geysir.
Directly adjacent to Geysir is Litli-Geysir (Little Geysir), one of the many geysers surrounding Geysir in the Haukadalur region. Source: C. Peterson, http://www.flickr.com/photos/clarissa/23527531/. Licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic licence.
Below, Geysir in action:
Jones, B., et al. (2007). The geological history of Geysir, Iceland: a tephrochronological approach to the dating of sinter. Journal of the Geological Society 164:1241-1252.
Pasvanoglu, S., et al. (2000). Geochamical Study of the Geysir Geothermal Field in Haukadalur, S-Iceland. Proceedings of the World Geothermal Congress 2000:675-680. Available at http://www.geothermal-energy.org/pdf/IGAstandard/WGC/2000/R0623.PDF. Accessed 28 August 2013.
Torfason, H. (2003). Geyser Area Geology. Geysir Center. Available at http://web.archive.org/web/20070416140350/http://geysircenter.com/english/geology.html. Accessed 28 August 2013.