Strokkur is Iceland’s most visited active geyser. One of the three major attractions on the world-famous Golden Circle sightseeing route, it is usually visited alongside Gullfoss Waterfall and Þingvellir National Park.
Strokkur is found in the Geysir Geothermal Area, titled after the Great Geysir, which lent its name to all others across the world. It is the greatest active geyser on site; Geysir itself is in a period of inactivity. Strokkur erupts more regularly than Geysir ever did, blasting water to heights of around fifteen to twenty metres every five to ten minutes, although it is known to reach up to forty metres.
Strokkur is the primary feature of the Haukadalur valley and the main reason why it is one of the most visited sites in the country. While Geysir will very occasionally still erupt to enormous heights, it is nowhere near reliable enough to justify the area’s popularity.
Haukadalur valley, however, has many other features that make it worth a visit. The natural beauty of the area is shaped by the forces of the earth; fumaroles, hot-springs, mud-pits and other little geysers are littered around, and the ground itself is dyed vividly by elements such as sulfur (yellow), copper (green) and iron (red).
Opposite the main geothermal area in Haukadalur Valley is a restaurant, cafe, hotel and luxury gift shop.
Active geysers like Strokkur are rare around the world, due to the fact that many conditions must be met for them to form. They are thus only found in certain parts of highly geothermal areas.
The first condition that is necessary is an intense heat source; magma must be close enough to the surface of the earth for the rocks to be hot enough to boil water. Considering that Iceland is located on top of the rift valley between the North American and Eurasian tectonic plates, this condition is met throughout most of the county.
Secondly, you will need a source of flowing underground water. In the case of Strokkur, this comes from the second largest glacier in the country, Langjökull. Meltwater from the glacier sinks into the surrounding porous lava rock, and travels underground in all directions.
Evidence of this flowing water can be found in Þingvellir National Park, where there are many freshwater springs flowing straight from the earth.
Finally, you need a complex plumbing system that allows a geyser to erupt, rather than just steam from the ground like a fumarole. Above the intense heat source, there must be space for the flowing water to gather like a reservoir. From this basin, there must be a vent to the surface. This vent must be lined with silica so that the boiling, rising water cannot escape before the eruption.
One of the main reasons that Geysir entered a period of inactivity was due to the fact soap used to be pumped into the vents to make the eruptions more dramatic; it damaged the structure of the vent and prevented water building up. Strokkur, therefore, is guarded against all interference, with chains keeping visitors a good distance away.
Unfortunately, however, there have been incidents where people have meddled with its natural state. For example, an artist called Marco Evaristti once poured food colouring into it to make the eruption pink. He defended himself by claiming that nature was open to artists to utiltise and the fact the colouring was all-natural, but he became a pariah amongst many Icelanders, and was arrested and fined (though never paid it).