The Earth Story

Visiting the areas around Reykjavik including Gulfoss, Seljalandsfoss, and the geothermal areas.

Strokkur

Along with the eponymous Geysir, this fountain of volcanically heated water that spouts up 15-40 metres into the air every 4-8 minutes is one of Iceland's most famous tourist sites. As the magma beneath cools, water percolating through the permeable basalt gets heated and rises back towards the surface. As it reaches the surface and cools, a form of silica opal called geyserite precipitates and can form a crust, blocking the vent until the pressure builds up and breaks through it, resulting in the next eruption. The other cause of pressurisation in geysers is cooler water capping the hotter water below, which heats up and boils, allowing the pressure to be released in the initial bubble seen bulging out in the slo mo video linked below. As the mass is expelled in the eruption, the pressure on the superheated (ie still liquid despite being at over 100 Celsius) water below goes down, allowing it to vaporise resulting in the steam eruption. The geyser needs some time to recharge its pressure, creating the gap between eruptions. The name comes from the Icelandic word for churn, which for those not familiar with the old ways was a pot in which milk and cream were beaten into butter.

Strokkur has been active since at least 1789, when a quake is thought to have opened its conduit. It blew regularly until 1896 when it was de activated by another quake rechanneling the heated water or blocking the vent, and was unblocked by people in 1963, recreating a long gone tourist attraction.

Loz

Image credit: Iurie Belegurschi

https://www.facebook.com/IurieBelegurschiPhotography?ref=ts&fref=ts http://www.photovolcanica.com/VolcanoInfo/StrokkurGeyser/StrokkurGeyser.html Slow mo eruption on vimeo:http://vimeo.com/54156546

About to burst

A geyser forms due to water being heated by the energy beneath the Earth’s surface. The water is heated past the normal boiling point of water, but remains in a liquid state because of the pressure of the water on top of it.

Eventually, enough water turns to steam that it begins blasting the column of water upwards. Once the first bit of water is removed, the pressure drops, causing more water to turn to steam and leading to a runaway eruption of the water. This specific burst is coming from Strokkur geyser, in Iceland. The term geyser originates from the Icelandic term geysir – the actual name for a different, but less active geyser at this site. Here the photographer captured Strokkur at the exact moment when the pressure of the steam was about to overcome the weight of the water above, triggering the eruption.

-JBB

Image credit: EGU Open Access http://imaggeo.egu.eu/view/779/

Drone overflight view of Strokkur geyser, Iceland

dji_mavic_images_

Geysir

The Geysir geothermal field is a 6 square-km active geothermal area in south-western Iceland. The area is home to many geysers and hot springs, including two well-known geysers named Geysir and Strokkur. The name Geysir was first used to describe the erupting columns of water in the hot springs in 1597 and means “gusher” or “one who rages” in Icelandic. Geysir is the largest hot spring in the geothermal field. It is first mentioned in literature following an earthquake in southern Iceland in 1294. It consists of a 3 m wide and 22 m deep shaft which opens into a 2 m deep and 15 m wide vent pool at the surface. Geysir’s discharge apron extends about 200 m from the vent and is made up of alternating units of siliceous sinters and ash beds containing a record of nearby eruptions. Sinter is a hard encrustation precipitated from the hot, mineral rich waters in the hot springs. Interestingly, Geysir is generally more active after a period of increased seismic activity in the surrounding area. Seismic activity can alter the path of water flow in the subsurface by blocking and creating channels. In extreme cases this can result in the formation or destruction of hot springs.

Geysir’s geothermal system is driven by heat from a magma body located 2 - 3 km beneath the surface. This magma heats a mixture of groundwater and runoff in cracks and fissures in the rocks, which drains into the shaft and is eventually brought back to the surface by an eruption. Eruptions are caused by the superheating of the water column at a depth of 10 m within the shaft. At this depth there is increased pressure due to the water volume above, and this causes the water at depth to boil at temperatures well over 100°C. As the hot spring begins to erupt, the water at shallower depths is converted to steam and starts to leave the shaft. This causes a chain reaction where pressure begins to decrease at depth, causing flash production of steam from the superheated water, which expands and travels up the shaft. This reaction is what drives the explosive nature of an eruption. One can tell when an eruption is imminent as a low rumbling noise coupled with expansion and bubbling of water at the surface. After an eruption, the vent pool empties and the water level drops between 16 and 22 m into the shaft. Water then rises at a rate of 2 m per hour until the shaft and vent pool are refilled. The water in Geysir is alkaline and has temperatures between 200 - 250°C at depth and between 71 - 80°C in the vent pool.

The frequency of Geysir’s eruptions is highly unpredictable. In the late 1700’s, during Geysir’s prime, its eruption columns would be 30 - 80 m high and occur in 5 to 10 minute bursts. The frequency of eruptions has been in decline since 1916. Due to the tourist industry in Iceland, several techniques have been used in the past to increase the frequency of Geysir eruptions. This included excavating the shaft and ‘soaping’ the geyser which causes bubbles to form and induces boiling. These methods are no longer being used as they negatively affect the natural balance of the hot spring. During periods where Geysir is active eruptions occur every 6 hours to 3 weeks. Today, Geysir is nearly completely inactive. It is common to see water continuously flowing out of the vent pool instead of building up to an eruption.

Another well known hot spring near Geysir is Strokker; “the churn”. Strokkur is currently one of the most active geysers in the Geysir geothermal field, with eruptions occurring every 10 to 15 min and eruption columns up to 40 m high. A unique feature of Strokker is the clarity of the water in the vent pool, which allows the steam to be seen bubbling to the surface before an eruption (pictured below).

Sources Thordarson, T., Höskuldsson, A. 2002. Iceland. Classic Geology in Europe. https://bit.ly/2IApDCO https://bit.ly/2DTtSrz https://bit.ly/2KD7tRe (paywall) https://bit.ly/2rWx6pl (paywall)

Image Sources https://bit.ly/2IyG6LT https://bit.ly/2rUbl9K

Geysir

The Geysir geothermal field is a 6 square-km active geothermal area in south-western Iceland. The area is home to many geysers and hot springs, including two well-known geysers named Geysir and Strokkur. The name Geysir was first used to describe the erupting columns of water in the hot springs in 1597 and means “gusher” or “one who rages” in Icelandic.

Geysir is the largest hot spring in the geothermal field. It is first mentioned in literature following an earthquake in southern Iceland in 1294. It consists of a 3 m wide and 22 m deep shaft which opens into a 2 m deep and 15 m wide vent pool at the surface. Geysir’s discharge apron extends about 200 m from the vent and is made up of alternating units of siliceous sinters and ash beds containing a record of nearby eruptions. Sinter is a hard encrustation precipitated from the hot, mineral rich waters in the hot springs. Interestingly, Geysir is generally more active after a period of increased seismic activity in the surrounding area. Seismic activity can alter the path of water flow in the subsurface by blocking and creating channels. In extreme cases this can result in the formation or destruction of hot springs.

Geysir’s geothermal system is driven by heat from a magma body located 2 - 3 km beneath the surface. This magma heats a mixture of groundwater and runoff in cracks and fissures in the rocks, which drains into the shaft and is eventually brought back to the surface by an eruption. Eruptions are caused by the superheating of the water column at a depth of 10 m within the shaft. At this depth there is increased pressure due to the water volume above, and this causes the water at depth to boil at temperatures well over 100°C. As the hot spring begins to erupt, the water at shallower depths is converted to steam and starts to leave the shaft. This causes a chain reaction where pressure begins to decrease at depth, causing flash production of steam from the superheated water, which expands and travels up the shaft. This reaction is what drives the explosive nature of an eruption. One can tell when an eruption is imminent as a low rumbling noise coupled with expansion and bubbling of water at the surface. After an eruption, the vent pool empties and the water level drops between 16 and 22 m into the shaft. Water then rises at a rate of 2 m per hour until the shaft and vent pool are refilled. The water in Geysir is alkaline and has temperatures between 200 - 250°C at depth and between 71 - 80°C in the vent pool.

The frequency of Geysir’s eruptions is highly unpredictable. In the late 1700’s, during Geysir’s prime, its eruption columns would be 30 - 80 m high and occur in 5 to 10 minute bursts. The frequency of eruptions has been in decline since 1916. Due to the tourist industry in Iceland, several techniques have been used in the past to increase the frequency of Geysir eruptions. This included excavating the shaft and ‘soaping’ the geyser which causes bubbles to form and induces boiling. These methods are no longer being used as they negatively affect the natural balance of the hot spring. During periods where Geysir is active eruptions occur every 6 hours to 3 weeks. Today, Geysir is nearly completely inactive. It is common to see water continuously flowing out of the vent pool instead of building up to an eruption.

Another well known hot spring near Geysir is Strokker; “the churn”. Strokkur is currently one of the most active geysers in the Geysir geothermal field, with eruptions occurring every 10 to 15 min and eruption columns up to 40 m high. A unique feature of Strokker is the clarity of the water in the vent pool, which allows the steam to be seen bubbling to the surface before an eruption (pictured below).

Sources Thordarson, T., Höskuldsson, A. 2002. Iceland. Classic Geology in Europe. https://bit.ly/2IApDCO https://bit.ly/2DTtSrz https://bit.ly/2KD7tRe (paywall) https://bit.ly/2rWx6pl (paywall)

Image Sources https://bit.ly/2IyG6LT https://bit.ly/2rUbl9K

Let’s do Strokkur geyser with a chill in the air for New Years

Strokkur geyser bursts, with a very nice winter steam cloud

Original caption:

Drone tour of Iceland

Excellent capture of eruption at Strokkur Geyser, Iceland - watch how the steam and bubble build before eruption.

Burst from Iceland’s Strokkur Geyser

Strokkur geyser erupting. Some time back we covered the rising bubble of this geyser about to erupt (http://tinyurl.com/kucd2pz). We wanted to share this image of the ensuing eruption. Loz Image credit: Auslandsoesterreicherflickraccountinhaber

Slow motion capture of Strokkur geyser, Iceland