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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 64.02°N
  • 21.17°W

  • 497 m
    1630 ft

  • 371801
  • Latitude
  • Longitude

  • Summit

  • Volcano

The Global Volcanism Program has no activity reports for Grensdalur.

The Global Volcanism Program has no Weekly Reports available for Grensdalur.

The Global Volcanism Program has no Bulletin Reports available for Grensdalur.

Basic Data

Volcano Number

Last Known Eruption



Unknown - Unrest / Pleistocene

497 m / 1630 ft


Volcano Types

Fissure vent(s)

Tectonic Setting

Rift zone
Oceanic crust (< 15 km)

Geological Summary

The small Grensdalur volcanic system (also known as the Hveragerdi system) lies at the eastern end of the Reykjanes Peninsula, SE of the Hengill volcanic system and south of the Hrómundartindur volcanic system. Grensdalur is the oldest of the three volcanic systems in the Hengill area and was last active during the Pleistocene. The Hveragerdi geothermal area contains high- and low-temperature geothermal features that include fumaroles, hot springs and pools, mud pots, and geysers, and provide heat to the town of Hveragerdi.


The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.

Clifton A E, Sigmundsson F, Feigl K L, Gudmundsson G, Arnadottir T, 2002. Surface effects of faulting and deformation resulting from magma accumulation at the Hengill triple junction, SW Iceland, 1994-1998. J Volc Geotherm Res, 115: 233-255.

Hansteen T H, 1991. Multi-stage evolution of the picritic Maelifell rocks, SW Iceland: constraints from mineralogy and inclusions of glass and fluid in olivine. Contr Mineral Petr, 109: 225-239.

Sigmundsson F, Einarsson P, Rognvaldsson S T, Foulger G R, Hodgkinson K M, Gunnar Thorbergsson G , 1997. The 1994-1995 seismicity and deformation at the Hengill triple junction, Iceland: triggering of earthquakes by minor magma injection in a zone of horizontal shear stress . J Geophys Res, 102: 15,151-15,161.

Zhanxue S, Armannsson H, 2000. Gas chemistry and subsurface temperature estimation in the Hveragerdi high-temperature geothermal field, SW-Iceland. Proc World Geotherm Cong, 2000, Kyushy-Tohoku, Japan, May 28-June 10, 2000, p 2235-2240.

The Global Volcanism Program is not aware of any Holocene eruptions from Grensdalur. If this volcano has had large eruptions (VEI >= 4) prior to 10,000 years ago, information might be found on the Grensdalur page in the LaMEVE (Large Magnitude Explosive Volcanic Eruptions) database, a part of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.


Feature Name Feature Type Elevation Latitude Longitude
Hveragerdi Thermal

Photo Gallery

Steam plumes, newly formed after a May 2008 earthquake, rise from the Reykir ("smokes" in Icelandic) geothermal area, with the town of Hveragerdi in the background. The Hveragerdi geothermal field lies within the small Grensdalur volcanic system. Grensdalur is the oldest of three volcanic systems in the Hengill area and was last active during the Pleistocene. The Hveragerdi geothermal area include fumaroles, hot springs and pools, mud pots, and geysers, and provides heat to the town of Hveragerdi.

Photo coutesy of the University of Iceland Hvergerdi Research Station, 2008.

Smithsonian Sample Collections Database

There are no samples for Grensdalur in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites

Large Eruptions of Grensdalur Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
MODVOLC - HIGP MODIS Thermal Alert System Using infrared satellite Moderate Resolution Imaging Spectroradiometer (MODIS) data, scientists at the Hawai'i Institute of Geophysics and Planetology, University of Hawai'i, developed an automated system called MODVOLC to map thermal hot-spots in near real time. For each MODIS image, the algorithm automatically scans each 1 km pixel within it to check for high-temperature hot-spots. When one is found the date, time, location, and intensity are recorded. MODIS looks at every square km of the Earth every 48 hours, once during the day and once during the night, and the presence of two MODIS sensors in space allows at least four hot-spot observations every two days. Each day updated global maps are compiled to display the locations of all hot spots detected in the previous 24 hours. There is a drop-down list with volcano names which allow users to 'zoom-in' and examine the distribution of hot-spots at a variety of spatial scales.
MIROVA Middle InfraRed Observation of Volcanic Activity (MIROVA) is a near real time volcanic hot-spot detection system based on the analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) data. In particular, MIROVA uses the Middle InfraRed Radiation (MIR), measured over target volcanoes, in order to detect, locate and measure the heat radiation sourced from volcanic activity.