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Geysir Volcano - John Seach
Iceland
64.32 N, 20.30 W
summit elevation 700 m
Stratovolcano
The Geysir geothermal area in Haukadalur is located in South Iceland, about 110 km from the capital, Reykjavik and 50 km from the sea, at approximately 100 m altitude.
The geothermal field lies in a shallow valley and is elongated in a north-south direction. The Geysir hot spring is situated at the bottom of the eastern slope of the rhyolitic dome Laugarfjall, which rises to 187 m.
The geothermal system is driven by volcanic intrusions in the roots of a now extinct central volcano. Rhyolitic rocks are found in Laugarfjall and the northern and eastern slopes of Bjarnarfell mountain. The lowlands east and south of the Geysir area are made of interglacial basaltic lava flows.
The geothermal waters contain sodium chloride and bicarbonate, with a high concentration of fluoride and boron, indicating reactions with acidic volcanic rocks. The radon concentration is extremely high, 10-100 times that found in other geothermal areas in Iceland.
Chemistry and isotopic composition indicate that the fluid originates from the mixing of run-off water from the Geysir geothermal field and local cold groundwater.
The flow rate from the Geysir field was 14 L/s in 1967 and reduced to 9 L/s in 1994.
1981 Eruptions
In 1981 eruptions of Geysir were produced by clearing the ditch around the vent, lowering the water table, and adding soap.
1935 Eruptions
Geysir reactivated in 1935 after a ditch was dug around the vent, lowering the water table.
1896 Eruptions
Before the 1896 earthquake, the Geyser erupted infrequently, with months sometimes between eruptions. After the earthquake geysir eruption to a height5 of 60 m occurred up to hourly. Activity declined gradually after 1896.
1630 Eruption
In 1630 the Geysir in Haukadalur erupted violently after being dormant for 40 years.
Geysir Volcano Eruptions
No recent magmatic eruptions. Currently geothermal activity.