Strokkur - watchers in the rain
Strokkur (Icelandic for "churn") is a geyser in the geothermic region beside the Hvítá River in Iceland in the southwest part of the country, east of Reykjavik. It is one of Iceland's most famous geysirs, erupting regularly every 4-8 minutes generally.
Notwithanding the rain, the spectacle of its eruption is awaited with great interest and attention.
Strokkur is part of a geothermally active site, with various mud pools, algal deposits and other geysers beside and around it such as Geysir.
How does it work?
Water at a depth of 23 metres is around 120°C, but cannot boil because of the weight of the water pushing down on it from above. When this water is forced up to around 16 metres, some of the water may be above boiling point, and this sets off the chain reaction we see. The pressure decrease allows more water to boil and flash boil into steam, which drives the unboiled water further up the conduit. As this happens closer and closer to the surface, with increasing velocity, the water and steam is forced out, and it is this mixture of water & steam that forms the eruption.