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                  <gco:CharacterString>Í vinnslu: Hitastigull á Íslandi -- Geothermal gradient in Iceland</gco:CharacterString>
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            <gco:CharacterString>[IS] Upplýsingar um hitastigul eru fengnar með mælingum á hita í grunnum, þurrum borholum, s.k. hitastigulsholum og hefur túlkun slíkra mælinga verið mikilvægur þáttur við jarðhitaleit á Íslandi á undanförnum áratugum. Niðurstöður hitastiguls eru vistaðar í gagnagrunni ÍSOR sem gildi hita á hverja 1000 m (°C/1000m). 
Gögn um hitastigul verið vistuð í gagnagrunn ÍSOR samhliða vinnu sérfræðinga ÍSOR við jarðhitaleitarverkefni um allt land. Markvisst átak var nýlega gert við undirbúning á verkefni fyrir umhverfis- orku- og loftslagsráðuneytið sem felur í sér uppfærslu á jarðvarmamati fyrir Ísland. Þá var gagnasafn ÍSOR um hitastigul uppfært með nýjum gögnum um túlkaðan hitastigul sem birt höfðu verið í skýrslum og greinargerðum ÍSOR frá árinu 2014, alls 790 nýjum eða uppfærðum gildum.

Borholum er mjög mismunandi dreift um landið, en mest er af hitastigulsholum nálægt þéttbýlisstöðum og þar sem kerfisbundin jarðhitaleit hefur farið fram. Á hálendinu hefur því hvert gildi hitastiguls mun meira vægi þar sem borholur eru færri. Öllum skilgreindum háhitasvæðum er gefinn hitastigull upp á 220°C/km og er það gildi sett í einn punkt á miðju svæði.

Við gerð hitastigulskorts var brúað á milli gilda með „Inverse distance weighted“ aðferð og er niðurstaðan rastakort með 500 x 500 m möskvastærð. Gildi hvers reits er reiknað miðað við gildi úr þeim 25 punktum sem næstir eru. Niðurstaðan var svo flokkuð og svæði teiknuð til sem sýna nokkur hitastigulsbil: &lt;50°C/km, 50-100°C/km, 100-150°C/km, 150-200°C/km og &gt;200°C/km, það kort er sýnt á mynd 4. 
Heimild: Gunnlaugur M. Einarsson, Guðmundur Freyr Jónsson og Steinunn Hauksdóttir (2025). Gagnasafn um hitastigul og uppfært hitastigulskort af Íslandi, ÍSOR 2025/054, 10 s

[EN] Information on geothermal gradients is obtained by measuring temperature in shallow, dry boreholes, so-called gradient wells. The interpretation of such measurements has been an important component of geothermal exploration in Iceland over recent decades. The results of geothermal gradients are stored in the ÍSOR database as temperature values per 1000 m (°C/1000 m).

Geothermal gradient data have been stored in the ÍSOR database alongside the work of ÍSOR specialists involved in geothermal exploration projects across the country. A targeted effort was recently undertaken in preparation for a project for the Ministry of the Environment, Energy and Climate, which involves updating the geothermal resource assessment for Iceland. As part of this work, the ÍSOR geothermal gradient dataset was updated with new interpreted gradient data that had been published in ÍSOR reports and documents since 2014, amounting to a total of 790 new or updated values. 

The spatial distribution of boreholes across the country is highly uneven, with most gradient wells located near urban areas and in regions where systematic geothermal exploration has taken place. In the highlands, each geothermal gradient value therefore carries significantly greater weight due to the lower density of boreholes. All defined high-temperature areas are assigned a geothermal gradient of 220°C/km, represented as a single point at the center of each area.

In producing the geothermal gradient map, interpolation between values was carried out using the “Inverse Distance Weighted” method. The result is a raster map with a grid resolution of 500 x 500 m. The value of each cell is calculated based on the 25 nearest data points. The results were then classified into zones representing several geothermal gradient ranges: &lt;50°C/km, 50–100°C/km, 100–150°C/km, 150–200°C/km, and &gt;200°C/km. 

Source: Gunnlaugur M. Einarsson, Guðmundur Freyr Jónsson og Steinunn Hauksdóttir (2025). Gagnasafn um hitastigul og uppfært hitastigulskort af Íslandi, ÍSOR 2025/054, 10 s</gco:CharacterString>
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