Thermal maps of Ireland
Geological Survey Ireland has produced a new suite of deep temperature maps for onshore Ireland. The maps represent two dimensional slices through the crust at depths of 2 km, 2.5 km, 3 km, 3.5 km, 4 km and 5 km. From the brochure produced, and I quote;
The maps have been prepared as part of Geological Survey Ireland’s National Geothermal Database project. Geological Survey Ireland provides geological advice and information to support the understanding of Ireland’s geothermal resources, the development of Irish geothermal energy policy and the growth of the Irish geothermal industry. Geological Survey Ireland, as a division of the Department of the Environment, Climate and Communications (DECC), has published these maps in fulfilment of a commitment under the All of Government Climate Action Plan. These maps are based upon a probabilistic thermal model of the Irish crust and as such, there is a degree of uncertainty inherent in the dataset (see Mather et al., 2018; Mather & Fullea, 2019). The temperature values mapped here should be viewed as guideline only and not as absolute values. The actual temperature at depth may vary from the temperatures shown in these maps. Nevertheless, the dataset is the most up-to-date and realistic representation of Irish crustal temperatures that is currently available. These maps are an important first step in the development of a fit-for-purpose National Geothermal Database. More technical information on how the maps were produced can be found using these 2 references: B. Mather, T. Farrell, J.Fullea, Probabilistic Surface Heat Flow Estimates Assimilating Paleoclimate History: New Implications for the Thermochemical Structure of Ireland Article, 2018 Journal of Geophysical Research: Solid Earth 123(12):10,951 - 10,967. DOI: 10.1029/2018JB016555 71 B. Mather and J. Fullea, Constraining the geotherm beneath the British Isles from Bayesian inversion of Curie depth: Integrated modelling of magnetic, geothermal, and seismic data Article, 2019 Solid Earth 10: 839–850. DOI: 10.5194/se-10-839-2019
These excellent maps and the report itself can be downloaded from here: https://www.gsi.ie/en-ie/publications/Pages/New-deep-temperature-maps-for-Ireland.aspx
Source Geological Survey of Ireland (GSI) - Deep temperature map at 2.0 km.
Temperatures in degrees Celsius. Scale approx. 1:2,000,000. Values range from 70°C to 230°C.
Source: Geological Survey of Ireland (GSI) - Deep temperature map at 4.0 km.
Temperatures in degrees Celsius. Scale approx. 1:2,000,000. Values range from 110°C to 280°C The maps as inferred from the journal titles above have been dominated by inversion techniques mainly from Magnetotelluric surveys. Ireland doesn’t have a lot of onshore wells or seismic surveys as the oil and gas madness never took off here. Is that good? Not sure, because we don’t know a lot about the subsurface of Ireland . The only thing that is guaranteed is a thermal gradient from the surface to the centre of the earth, which is approx. 60000 C (surface of the sun temperatures). The maps imply temperature gradients of 100 C/km in the top 2 km in the North. These are comparable to gradients in Iceland above the Hengill geothermal field and twice the temperature gradient in the active geothermal energy site in the Taupo Volcanic Zone where you can see steam rising from the ground. Measured values from borehole temperatures in the top km are rarely > 35 C/km in Ireland. I suspect there could be an issue with the inversion of the Curie Depth based on the magnetics which is screwed by the presence of highly magnetic basalts, but I would have to chat with the map creators. Maps look damn good though and give us a low resolution indication of some juicy sites.
(Magnetotellurics (MT) is a passive geophysical method which uses natural time variations of the Earth's magnetic and electric fields to measure the electrical resistivity of the sub-surface. More information can be found googling any university geophysics textbook, this is a particularly well read one: https://www.amazon.com/Applied-Geophysics-W-M-Telford/dp/0521339383?asin=0521339383&revisionId=&format=4&depth=1
About the Author
Dr Brian O’Connell
Having just returned to Ireland after 15 years around the world in the Oil & Gas Industry, I see a future for Geothermal Energy in Ireland.
Quick description, Physics degree in UL, PhD in Geophysics In NUIG, worked oil & gas industry around the world for 15 years & just completed a MSc in Smurfit, Renewable Energy and Environmental Finance. Degrees are easy, geoscience is not.