‘Practically useful, scientifically important, and to the honour of the country’: geological maps and services provided by the Geological Survey of Norway these past 165 years Open Access

‘If a picture is worth a thousand words, then a geological map is worth a million’. The quote is taken from a US Geological Survey Open File Report where it is concluded that the utility value of geological mapping is substantial (Cobb 2002). It is well documented that geological mapping creates and secures values. By mapping the underground, we can discover metals and minerals that we need for industrial and technological development and to build our homes, daily utilities and infrastructure. We need knowledge of the geology to see where we can find groundwater and nutrient-rich soil, and to know where the subsoil is radioactive and where the ground is unstable. We need geological knowledge to be able to predict how interventions in landscapes will affect our communities and make us vulnerable to geohazards such as landslides and floods. Further, without basic geological information, we cannot properly address any societal impacts from future climate changes and find minerals and materials for technologies needed to move away from fossil fuels and towards carbon-lean, green energy options.

As pointed out in the Geological Society of America's position statement ‘The Value of Geological Mapping’, economic studies all show a positive benefit-to-cost ratio for the geological mapping activity, spanning from 4:1 to >100:1 (Berg et al. 2019, pp. 19–23). The statement is also supported by a study carried out by researchers at Luleå University of Technology (Häggquist and Söderholm 2015), where they summarize the results of 20 years of research on the value of geological information and soil observations. One example is from Spain, where a major survey was carried out with detailed geological maps on a scale basis of 1:30 000 to 1:50 000. The survey was based on interviews with around 2200 users of geological data, and the conclusion was that for every Euro that society invests in public geodata, 18 Euros return in value creation and concrete income.

The financial returns on the investments in geological mapping cover both direct benefits and avoidance of future financial loss (Häggquist and Söderholm 2015); and collecting geological knowledge and making data and maps freely available as a public good are very profitable for society. Such maps and linked data are particularly useful when they are accessible in standardized digital formats and provided through online open public access. Geological maps and freely available geological data therefore become resources that can be used indefinitely. In addition to multiple essential direct uses, geological maps and data are an essential starting point for a series of more specialized investigations and integrated assessments of our living environments.

In Norway, mining activities are documented back to around 1170 (Akersberget Mine, a small silver mine in Oslo), while formal education in geology started with the establishment of the School for Mining Engineers at Kongsberg Silver Mines in 1757 (Fig. 1). When the University of Oslo was founded in 1811, the mining school was moved to Christiania (now Oslo), where the second Professor in Geology, Baltazar M. Keilhaug (1797–1858) became the first pioneer of regional geology with his main work ‘Gæa Norvegica’, published in 1850 (Oftedahl 1980). Keilhaug's successor, Theodor Kjerulf (1825–88) established the Geological Survey of Norway (NGU) and started the publication of a national series of geological maps. In the first years, the Geological Survey shared offices at the university in the capital Christiania. The first mapping of soil and bedrock carried by Theodor Kjerulf was conducted in different districts in southern Norway, while his assistant Tellef Dahll (1825–93) was sent out to map the remote high north. The present paper presents an overview of geological mapping carried out by the NGU since 1858 while focusing on activities and products produced in the present millennium. Historical facts and figures prior to 1983 are collected from the NGU's 100th anniversary publication by Ingvaldsen (1983), and prior to 2008, from the NGU's 150th anniversary book Kartleggerne (in Norwegian; in English, The Mappers) by Børresen and Wale (2008).

NGU was created through a Royal Resolution by King Oscar I on 6 February 1858. When Professor Theodor Kjerulf forwarded the plans for a National Geological Survey 2 years earlier, he argued to the Ministry of the Interior that such an institution would be ‘practically useful, scientifically important, and to the honour of the country’ (Smelror 2008, p. 19; see also Børresen and Wale 2008; Smelror 2020).

At the time when the systematic geological mapping began, the living conditions were very different from today’s Norway. The population was close to 1.6 million and the majority subsisted on agriculture. The road network was poorly developed and most of the communication took place on foot and by horse and cart, or by boat along the coast. The first railway connection, between Christiania (Oslo) and Eidsvold, was opened in 1854. There was little industry in the country, but the mines at Kongsberg and Røros, founded in the first half of the seventeenth century, were significant businesses (Ingvaldsen 1983).

Mapping of the bedrock in Norway was to become the main task for the Geological Survey, whereby creating new opportunities for exploitation of natural resources and economic modernization. This mission was to go hand in hand with research that could provide new knowledge on the country's geological history and bedrock formation, and strengthen the Norwegian geoscientific community. The Norwegian mainland, the coast and the continental shelf exhibit a great variety in topography and geology. For many years, the geological mapping took place in remote and basically unexplored land areas. As pointed out by Børresen and Wale (2008, p. 11):

It was therefore not without reason that literary historian Gerhard Gran claimed in 1905 that through their works, geologists, like poets and painters, had conquered community after community, so that Norwegian were finally able to say that they owned their land.

In 1905, Norway was separated from the union with Sweden. The mainland bedrock geology of Norway is dominated by rock complexes of Precambrian to Early Paleozoic age, of which, as much as 70% has been involved in the Caledonian Orogeny (Sigmond and Roberts 2007). Less than 2.5% of the mainland bedrock comprises post-Caledonian Devonian molasse, Carboniferous and Permian sediments, basalts and rhomb porphyrites (Oslo Rift) and Jurassic–Cretaceous sedimentary rocks (Andøya and basins below the seabed in Beistadfjorden, Sortlandsundet and some other areas).

According to the instructions given by the Ministry of the Interior in 1858, the main series of geological maps to be produced by the Geological Survey should be made at a scale of 1:100 000, but other scales were also accepted when necessary. In the first years, manager Kjerulf and his assistant Tellef Dahll were the only employees (Fig. 2). According to the instructions from the Ministry of the Interior, they were obliged to spend as much time in the field as the seasons allowed. In the pioneering years between 1858 and 1880, three major regional bedrock maps were completed: southern Norway (scale 1:400 000) in 1865; Trondheim diocese (scale 1:800 000) in 1876; and northern Norway (scale 1:1 000 000) in 1879 (Fig. 3). In many ways, the maps and associated descriptions answered to the main ambitions: economic (‘practically useful’), scientific (‘important’) and cultural (‘honourable to country’). We should also note that already in 1803, the Norwegian natural scientist and philosopher Henrik Steffens had made a proposal for the geological mapping of Norway. The proposal was turned down, but had it been realized, the geological map could possibly have preceded William Smith's most famous geological map of Britain (i.e. ‘The Map that Changed the World’) published in 1815 (Winchester 2001).

In addition to the three national bedrock maps mentioned above, 23 maps at scale 1:10 000 had been published by 1890. More geological mapping followed, and in 1891, NGU started its own publication series, which came to include new maps and descriptions (Fig. 4). In 1892, a committee assigned by the government recommended that the Survey concentrate on producing maps at scale 1:400 000 before continuing with rectangle maps at scale 1:100 000. The argument was that the knowledge of the country's overall geological framework was still very poor, so that one was not able to extract enough value from the more detailed geological maps. However, only four maps at scale 1:400 000 in southern and western Norway were compiled, and in 1907, Professor in Geology W. C. Brøgger argued to the Parliament that the geological maps at scale 1:400 000 overview series were not particularly useful (Ingvaldsen 1983). In the years to come, compilation of geological maps at scale 1:100 000 continued, and the map series also came to include Nordland County. The results from the geological mapping were also transformed to the national map series at scale 1:250 000, which served as a much better topographic layout than the older general maps.

People who experienced the early years of geological mapping after the turn of the century have recalled that the atmosphere was filled with high expectations (Ingvaldsen 1983). At the Jubilee Exhibition in 1914 (100 years after the Norwegian Constitution was signed), NGU presented a series of regional, as well as more detailed, maps, together with representative bedrock samples. The geological maps included southern Norway at scale 1:1 000 000, compiled by A. Werenskiold; a map of Helgeland-Salten and one of Lofoten-Vesterålen at scale 1:100 000, compiled by T. Vogt; a map of iron-ore deposits in southern Norway at scale 1:500 000 and one of Balangen mining district at scale 1:50 000, both compiled by S. Foslie; and a map of limestones and other useful rocks in northern Norway at scale 1:1 000 000, compiled by J. Oxaal. The mapping activities expanded, new geologists were hired at the Geological Survey and from 1915, they were given the new employment title ‘Geologist of the State’. The nineteenth and twentieth centuries were periods with major national and international changes, with up and downturns, but in the years between the two world wars, the Survey's publication series came to reach more than 150 items. The main geological map series was continued with sheets at scale 1:100 000.

Mapping of surficial deposits, mainly soils for agriculture, was initiated with T. Kjerulf's work in Aker, Romerike, Hadeland, Ringerike and areas around Lake Mjøsa already in 1858–62, but production of so-called Quaternary maps first took off in 1936 under the management of G. Holmsen. In the years 1949–60, six Quaternary maps at scale 1:250 000, covering areas in southern Norway were published.

The bedrock mapping expanded into the more remote and less detailed mapped areas of the country, and in 1953, a new national bedrock map at scale 1:1000 000 was presented by O. Holtedahl and J. A. Dons (Fig. 5). However, through the years between the world wars and in the years to follow, several political voices had criticized the Geological Survey for being too little oriented towards the needs of the mining industry and for not being very productive. The Geological Survey was challenged by the State Raw Materials Laboratory, and from 1934, the newly formed institution Geophysical Prospecting did the same (Børresen and Wale 2008). In 1957, the Norwegian Parliament voted ‘yes’ to the governmental proposal to merge the Geological Survey with the two above mentioned institutions to form a new united institution, and in 1961, the Survey moved from the capital Oslo to the city of Trondheim, Mid Norway.

By the end of 1961, a new national plan for the geological mapping of Norway was submitted to the Ministry of Industry and sent out to several institutions for comments and recommendations. The plan was to cover 32 geological maps at scale 1:250 000 within the upcoming 20 years. In the spring of 1965, the plan was approved by the Norwegian Parliament, but later barely provided with any financial resources. When NGU celebrated its 125th anniversary in 1983, parts of the mapping programme were still not fulfilled. In the NGU 1858–1983 commemorative publication, Director K. Ingvaldsen (1983) wrote that the series was likely to be completed in 1995. Here, we must acknowledge the many very devoted and highly qualified geologists who contributed to the mapping programme through the last century. Most of them are given due credit by their names on the published maps. Geologists involved in the mapping of Norway not only included employees at NGU, but also academics and students from domestic and foreign universities and research institutes (Fig. 6).

The 1960s also brought a new era in geological exploration and the economic history of Norway with the discovery of oil and gas on the Norwegian Continental Shelf. The Geological Survey had experience from geophysical mapping on the mainland and contributed with airborne geophysical measurements. From 1965–75, geophysicists from NGU collected 225 000 profile kilometres of aeromagnetic data from the shelf (Ingvaldsen 1983). The measurements were initiated with four profiles between Norway and Denmark in 1962, in cooperation with the University of Bergen. In the following year, 30 new profiles were measured as a contribution to the Norwegian–Danish–German Skagerrak Project. Later in 1963, aeromagnetic profiles were measured from the mainland and on the continental shelf at eight different transects from Møre to Lofoten (Mid to North Norway). All profiles revealed variable thick successions of sediments above the magnetic basement rocks. This was a clear indication of potential hydrocarbon bearing strata on the continental shelf. Between 1965 and 1977, new campaigns with aeromagnetic mapping were carried out, spanning offshore areas from the North Sea in the south towards the Russian border in the north. Some profiles were also measured across the Arctic islands of Svalbard. Thick successions of sediments, from 5 to 10 km below the seabed, were identified and the petroleum companies showed great interest in the aeromagnetic data (Ingvaldsen 1983).

However, offshore geological mapping was not a primary task for NGU. Ingvaldsen (1983) writes that the political interest in financing mapping of the shelf was limited, and the Geological Survey lacked the necessary resources. In retrospect, it is also reasonable to assume that the limited interest was caused in part by NGU itself. In a ‘famous’ letter from NGU to the Norwegian government in 1958 (Letter to the Norwegian Ministry of Foreign Affairs dated 25th February 1958), it is stated that ‘One can disregard the possibility of coal, oil or sulfur being found on the continental shelf along the Norwegian coast’, a conclusion that proved totally wrong as it was basically founded on a complete lack of data and knowledge. However, in the introduction to the letter, it was stated that,

[I]t must be emphasized that the report does not provide any thorough analysis of the complicated problems regarding the geology of the continental shelf and possible sources of raw materials along the Norwegian coast.

In 1972, the Norwegian Petroleum Directorate (NPD) was established as the government agency to facilitate long-term access to resources from the Norwegian petroleum activities on the shelf. In the following years, the Geological Survey continued with airborne geophysical surveys covering large areas of the shelf, and with integrated geological and geophysical research in cooperation with NPD and the petroleum industry. A magnetic anomaly map of Norway's onshore and offshore areas at scale 1:3 million was published in 1997 (Olesen et al. 1997), and a gravity anomaly map at the same scale, in 2000 (Skilbrei et al. 2000). Into the new millennium, new surveys were carried out. As an example, one could mention that in the year when NGU celebrated its 150th anniversary (2008), aeromagnetic measurements were conducted covering an 80 000 km² area in the Barents Sea, followed up with surveys in the Barents Sea covering 105 000 km² in 2009, an area corresponding to one-third of the Norwegian onshore land coverage. The cooperation with NPD and the industry has continued, and as more high-quality datasets are collected, new and more detailed geophysical maps and online services are generated and made public (Fig. 7).

During the years from 1970 to the turn of the millennium, geological mapping was expanded to include new purposes and target areas. In addition to bedrock and surficial (Quaternary) deposits, geochemical, hydrological and marine mapping became major tasks for NGU. Mapping of ‘sand and gravel on the shelf’ started in 1975 and included the Continental Shelf Institute and Norwegian Hydrographic Services as partners. Geochemical mapping of stream sediments in the late 1970s was carried out in parts of the Oslo Region, with a focus on molybdenum mineralization.

After the Norwegian reform of the county councils in 1976, NGU gained new and important users of geological information, and regional programmes were established in cooperation with some of the counties. The extensive mapping carried out during the Finnmark County Programme in the 1970s and 1980s in the northernmost part of Norway provided the basis for a regional bedrock map at scale 1:500 000. The bedrock mapping was supported by regional-scale airborne magnetic surveys, and the combination of magnetic and gravimetric anomaly maps with field observations and petrophysical data provided new knowledge of important regional tectonostratigraphic relationships, for example, how the Paleoproterozoic Raipas Supergroup continues underneath the Caledonian Nappes in western Finnmark.

In addition to magnetic measurements, onshore airborne measurement came to include radioactive radiation. When one of the four reactors in the Chernobyl nuclear power plant exploded on the night of 26 April 1986, radioactive iodine and cesium spread over large areas of Europe, including Norway, where high concentrations were measured in Mid Norway. Through measurements of radioactive fallout, NGU's geological expertise extended across the country as never before (Børresen and Wale 2008). Airborne mapping of fallout from Chernobyl continued in 1991, with new surveys and the production of five maps at scale 1:100 000 showing the fallout of Caesium-137 in various counties in Central Norway. The mapping of radon radiation risks was followed up with airborne gamma-ray spectrometer surveys and whole-rock chemical analyses of bedrock samples covering large tracts of Norway (Heincke et al. 2008; Smethurst et al. 2008, 2017; Watson et al. 2017; Olesen et al. 2022). A national radon risk map at scale 1:1 000 000 was compiled by Smethurst et al. (2014). More recently, a new radon risk map using Trøndelag County as a test area was published by Olesen et al. (2022) (Fig. 8).

Through the 1970s and 1980s, extensive mapping through seismic surveys and exploration drillings was carried out on the Norwegian continental shelf, and this paved the way for an integrated bedrock map covering both the Norwegian onshore and offshore areas. The compilation of such a map took place from 1986 to 1992, with a bedrock map at scale 1:3 million published in 1992 (Sigmond 1992).

In 1990, a map at scale 1:1 million showing the distribution of surficial deposits in Norway was completed (Thoresen 1990). Here, the surficial deposits were classified according to their genesis and thickness, based on all available Quaternary maps compiled by the Geological Survey. Surficial deposits represent an important non-renewable natural resource, and the latest update of the map was presented in 2013.

After finishing the Finnmark Programme in northernmost Norway, a new county programme was started in Troms. The programme lasted from 1997 to 2002 as a cooperation between NGU and the Troms County Municipality. The Troms Programme included the mapping of bedrock, surficial deposits, mineral resources and groundwater. One of the succeeding products was a popular science book of stories on the Troms Country geological history, landscape and geological resources, which included geological maps and photos of the scenic mountainous landscapes in this part of North Norway (Dahl and Sveian 2004).

Later, in 2002, an update of the 1:3 million scale onshore–offshore bedrock map became a part of a major geological map covering land and sea areas of Northern Europe (Fig. 9; Sigmond 2002; Sigmond and Roberts 2007). This map was the result of cooperation between NGU and the geological surveys of 21 other countries under the aegis of the Commission for the Geological Map of the World (CGMW). The map, at 1:4 million scale (Sigmond 2002), presented for the first time the pre-Quaternary bedrock of both land and sea areas of Northern Europe. A collection of short descriptions of the geology of countries and sea areas within the extensive region covered by the map was edited and published by Sigmond and Roberts (2007).

In combination with the development of new map products at various scales, the development of computer technology and hardware capacities presented new means and opportunities to provide geological information to the growing variety of public and private users. Development of databases and digital maps became main tasks of the Geological Survey, and the digital revolution led to a fundamental change in NGU's map production and the diffusion in and mediation of geological information to society (Børresen and Wale 2008; Smelror 2008).

With the advent of the new millennium, NGU initiated NGU Digital, a major programme with the ambition to digitalize the geological maps, reports and publications published through the history of the Geological Survey, and to make the products available on the internet. In 2001, NGU was given the ‘Special Achievements in Geographic Information Systems (GIS) Award’ at the ESRI User Conference in San Diego. In the following years, Norway became an international leader in the digital processing of geographical and geological information, with several map and geodata services made publicly available. Through the NGU Digital initiative, NGU established several geological databases and internet solutions. This was followed up through the establishment of the national programme Norge Digital and Geonorge (www.geonorge.no), the national website for map data and other location-based information in Norway.

Structural geology and mapping of major bedrock lineaments had always been an important part of the bedrock mapping programmes at the Geological Survey. In addition to field observations, aerial photos and Landsat satellite images became important tools for identification of regional delineations and structural weakness zones both on regional and local scales. Mapping of underground weakness zones and fractures in the bedrock was raised on an agenda linked to both underground tunnelling projects and identification of areas subjected to rockfalls and landslides. In 2001, NGU was given the responsibility for a national portal for maps and information on landslides in Norway (www.skrednett.no), and in 2004, NGU became responsible for the coordination of landslide mapping in Norway. In the following years, the database expanded with data provided by NGU, the Norwegian Energy Regulatory Authority (NVE), Norwegian road and railway authorities, Norwegian Defence and the Norwegian Geotechnical Institute (NGI). Two years earlier, when the International Centre for Geohazards was established in 2002 as a collaboration between the Norwegian Geotechnical Institute, NORSAR, the University of Oslo, Norwegian University of Science and Technology and NGU, the Geological Survey became responsible for the project ‘Rockslope Failures – Models and Risk’. In addition to classical bedrock mapping and geophysical measurements, GPS tracks of rock movements, investigations of permafrost, 3D laser-scanning and satellite radar measurements (i.e. radar interferometry/InSAR) became major tools for the modelling and risk assessments (https://insar.ngu.no/) (Figs 10 & 11).

To serve the constantly increasing need for geological knowledge and data for cost-effective and safe development of infrastructure in Norway's most populated areas, a new integrated regional mapping programme named Geology in the Oslo Region (GEOS), comparable to the previous programmes in North and Mid Norway, was started in 2003. Covering the most populated areas in Norway, the programme started with aeromagnetic surveys both with fixed-wing aircraft and helicopter. New baseline data were collected, and new information of relevance for areal planning, underground development, geothermal heating, supply of groundwater and environmental problems related to radon was made available to the public. The series of geological maps also included a map showing zones with deep weathering of the crustal basement, based on aeromagnetic data and covering an area of about 10 000 km² from Hadeland and Romerike in the north to Fredrikstad and Skien in the south.

In the Oslo Region, rockfalls, collapses and water leakage in several key infrastructure road and railway tunnels have led to costs increasing three-fold and more, relative to the budgets. Here, maps showing probable and potential areas of deep weathering and weakness zones became a strong advertisement for how ‘practical[ly] useful’ geological/geophysical maps and data are for planning of major infrastructure developments (Olesen and Rønning 2008). After the collapse in the Hanekleiv tunnel on the E18 south of Oslo on Christmas Day in 2006, the interest of NGU maps showing potential zones of deep weathering was raised on national television news. The question was: ‘Why didn't the tunnel contractors foresee this incident?’ In fact, this would not have been straightforward since a map of the weakness zones was only made after the construction of the tunnel was finished. Another major asset gained from the GEOS project was the new bedrock map at scale 1:250 000, compiled by O. Lutro and Ø. Nordgulen. The map, published in 2008, became a national bestseller.

As a part of the GEOS project, marine mapping of bathymetry, seabed sediments and pollution was carried out in the inner Oslo-fjord. As expected, high concentrations of heavy metals were discovered. Prior to that, NGU had started marine mapping along coastal areas and in Skagerrak, where the Skagerrak Project came to be the first major task of the MGK programme (Marine Geological Mapping of Norwegian Sea-floor Areas). The MGK programme was a joint effort of six governmental institutions with expertise in marine mapping and research (Longva and Thorsnes 1997).

In 2005, the launch of the Mareano programme followed as a major breakthrough in marine mapping in Norway (Thorsnes et al. 2020; Bøe et al. 2022; Doland et al. 2022). The Mareano programme continues today, and through this comprehensive and advanced mapping programme, data on depth, bottom conditions, biological diversity, habitat types and pollution in sediments in Norwegian coastal and offshore marine areas are collected, organized and made available to a series of end-users and to the public in general. The internet portal www.mareano.no was launched in 2004 (Figs 12 & 13). The web portal was the result of cooperation between several national institutions, including NGU, the Marine Research Institute, the Directorate of Fisheries, the Norwegian Petroleum Directorate, the Norwegian Mapping Authority, the Norwegian Environmental Agency, the Norwegian Defence Research Establishment and the Norwegian Polar Institute.

During its first phase from 2006–10, priority was given to Mareano baseline mapping in the Barents Sea and areas off Lofoten. A new national management plan for these areas was presented in 2011, and results from the Mareano programme contributed significantly with marine benthic knowledge to the management plan revision. In its second phase (2011 onwards), Mareano mapping has continued in the Barents Sea, inclusive of the new Norwegian marine territorial areas included after the agreement of the Norwegian–Russian offshore borders in 2010. Due to the scheduled revision of the management plan for the Norwegian Sea in 2014, priority was also given to the extensive shelf and deep-sea areas. Since then, the Mareano programme has expanded to also include parts of the North Sea. From its launch in 2005, the total budget of the mapping programme has grown from 5 million NOK/year to more than 100 million NOK/year. Between 2006 and 2019, more than 200 000 km² of seabed have been mapped, corresponding to about 10% of the Norwegian offshore area (Bøe et al. 2022).

In 2009, NVE became the national authority for mapping and securing areas subjected to natural hazards, like floods and landslides, and took over the responsibility for the internet portal skrednett.no from NGU. As the geological expert organization, NGU continued to map areas at risk of rockfalls and landslides (Fig. 9), now with fixed annual financial support from NVE. In the mapping programme, priorities also came to include areas at potential risk for quick clay landslides and mountain slopes at risk due to unstable soil.

By 2012, all geological maps published by the Geological Survey were digitalized. However, large land areas still remained to be mapped. At scale 1:50 000, about 55% of the mainland was covered by bedrock maps, while only 23% of the land area was covered by surficial deposit maps of the same resolution. On the first day of 2012, a major landslide at Byneset in the Trondheim area raised attention to the need for speeding up the mapping of areas at risk of similar landslides, i.e. areas with marine sediments, uplifted after the last glaciation, today being exposed to farmland and urban populated areas and subjected to rainfalls washing out the salt that had previously stabilized the Quaternary sea-floor clay deposits. Eight years later, the devastating quick clay landslide at Ask in Gjerdrum, north of Oslo, on 30 December 2020 became a new tragic reminder of the need for landslide risk maps. Here, 11 people lost their lives, 1600 people were evacuated and houses and infrastructures were destroyed (NOU 2023).

A few years earlier, in 2018, an innovative, open-access mapping service allowing users to see where both buildings and ground surfaces move throughout the country had been launched (Figs 10 & 11). The nationwide InSAR service was provided through a collaboration between NGU, the Norwegian Water Resources and Energy Directorate (NVE) and the Norwegian Space Centre. Pioneering development on the application of satellite radar measurements (i.e. radar interferometry/InSAR) to map deformation in the landscape, including subsidence in cities and movements in unstable mountain slopes, was carried out and led by John Dehls. Since its early start around 2000, the research institute Norut, now part of NORCE (Norwegian Research Centre AS), has been a key partner of NGU in the development of the InSAR technology for mapping of unstable ground.

Another risk displayed on maps is earthquakes. In general, the Norwegian mainland has not been exposed to severe earthquakes in the past decades, but neo-tectonic movements are measured and Neogene to Quaternary motion and deformation is recognized in many places both onshore and offshore (Olesen et al. 2013, 2018; Keiding et al. 2015, 2018). In 2018, results from the Neotectonics in Norway (NEONOR) programmes (Olesen et al. 2018) were presented on a neo-tectonic map of Norway and adjacent areas at scale 1:3 million (Keiding et al. 2018). The map includes information on nine major components in the covered area: ocean spreading, Neogene uplift and erosion, offshore Pliocene and Pleistocene deposition, submarine slides, Quaternary volcanism on Svalbard and Jan Mayen, glacial isostatic adjustment, the postglacial Lapland Fault Province and state of stress and seismicity (i.e. earthquake locations and magnitudes during 1980–2012 from the Earthquake Catalog of Northern Europe (FENCAT)).

Along with the development of digital maps and more user-friendly database services, NGU started to fully develop workflows from field observations and registrations to final online map services widely available to the public. The first project where all tasks were fully digitally conducted was the Vest-Agder surficial mapping project in 2014, where all observations were continuously stored on a robust laptop out in the field, and all preparatory work, data-processing, interpretations and corrections were on the same GIS platform, both in the field and in the office, before all data were made available on the internet at www.ngu.no.

In 2013, the Norwegian government presented a strategy for the mineral industry in Norway. Prior to that, in 2011, the government had allocated special funding (25 million NOK/year) for geological mapping and investigations of mineral resources in North Norway (Nordland, Troms and Finnmark counties). Compared to the neighbouring countries Sweden and Finland, mapping and studies of mineral deposits had fallen behind on the Norwegian mainland. Instead, more resources had been allocated to mapping and research on the continental shelf. While the areal coverages of airborne geophysical surveys on land areas were nearly 100% in Sweden and Finland, Norway was left with only 14%. One should note that NGU is responsible for the managing of regional databases of gravity and magnetic data for both mainland Norway and the Norwegian Continental Shelf (https://geo.ngu.no/geoscienceportalopen/search), and that the portal and its services include both these datasets.

One goal reached through the Minerals in Northern Norway programme (MINN) was increasing the geophysical survey coverage to 75% of the land areas. Through the MINN programme, 20 600 km² of high-resolution, helicopter-borne geophysical data (magnetic, electromagnetic and radiometric) were collected in the northern counties of Nordland, Troms and Finnmark. In addition, 89 100 km² were covered by fixed-wing aircraft surveying. New high-resolution aeromagnetic and radiometric surveys provided far better links between the geophysical anomaly pattern and the bedrock and geological structures. As an example, the data from the Caledonides and the Archean–Paleoproterozoic crystalline basement of North Troms and Finnmark provide very good evidence for the continuation of diverse Precambrian greenstone belts and granulite terranes beneath the magnetically Caledonian nappes (Nasuti et al. 2015).

In addition to the geophysical surveys, the MINN programme covered mapping of bedrock and surficial deposits, geochemical analyses and detailed field observations (Sandstad 2015). In some seasons, up to 60 people were engaged in the mapping. The areas of detailed bedrock mapping were expanded, older maps were revised and updated and new structural models were introduced (cf. references in Sandstad 2015). The geochemical analyses included 2200 till samples covering the whole northern Norway, combined with more detailed studies in selected areas like Nordkinn and Tysfjord, where anomalous values of rare earth elements (REE) and various other special metals were mapped (Sandstad 2015).

As part of the national mineral strategy, in 2013, the government also allocated 10 million NOK as a start-up fund for airborne geophysical surveys in South Norway and the Minerals in South Norway Programme (MINS). The goals and methods were the same as for the MINN programme. Both the MINN and MINS programmes were continued in 2014 and 2015.

In 2011, the European Commission started to assess and provide a list of critical raw materials (CRMs) for the EU economy within its Raw Materials Initiative, an assessment updated every 3 years. Nine years later, the list had grown to 30 minerals and materials, mainly used in energy transition and digital technologies. In March 2023, the EU Critical Raw Materials Act (https://ec.europa.eu/commission/presscorner/detail/en/ip_23_1661) was proposed as a framework for ensuring a secure and sustainable supply of critical raw materials. However, in Norway, the government that took over in 2013 decided to stop the MINN and MINS programmes in 2016, and geological mapping for critical minerals in Norway came to a halt. Exploration and mining companies, as well as investors, responded by reducing activities in Norway. Norway fell behind on the Investment Attractiveness Index and the Policy Perception Index in the Fraser Institute Annual Survey of Mining Companies.

Today, critical minerals are high up on the agendas of most countries. More minerals are needed to produce the materials for everyday life new and smart technological solutions, and to provide, store and distribute environmentally friendly energy. In the years to come, the extent of recycling will be higher than the supply from new resources for many metals and minerals. Until then, we need to increase our mining activities, since increased exploration and new mining are needed for a shift to greener, more environmentally friendly energy (Smelror et al. 2023). In 2016, NGU published an updated ‘Minerals Needed for the Green Economy’ (Heldal et al. 2019). As documented prior to MINN and MINS, and through the results of the programmes, Norway has proven commodities and potential resources to provide minerals and materials for ‘The Green Stone Age’ (Gautneb et al. 2022; Jonsson et al. 2022; Smelror et al. 2023).

High quality mapping of bedrock and mineral resources requires support from laboratories to provide good analytical measures; and in 2017, the Norwegian Research Council financed the start-up of new laboratories for mineral and material characterization at NGU, Norwegian University of Science and Technology (NTNU) and the SINTEF Group (the Norwegian Laboratory for Mineral and Materials Characterization – MiMaC); and with the change of government in November 2021, newly allocated fundings for mineral mapping were added to the NGU budget in 2023 (10 million NOK).

In addition to the ‘green shift’, ‘blue growth’ became a political slogan in the first decade of the present millennium. The Norwegian coast, including the Norwegian fjords and islands, stretches for more than 104 000 km from the Barents Sea to Skagerrak, and the continental shelf and deeper oceans covers more than 2 million km². Mapping through the Mareno programme was mainly carried out on the shelf, while coastal surveys were restricted to more local projects such as that in Astaforden, southern Troms. The Astafjorden project became a pilot for nearshore marine geological surveys, providing key information for the management of coastal areas and planning of marine infrastructures, including aquaculture installations. When the project was terminated in 2011, an area of 3600 km² had been mapped and sampled. At that time, Astafjorden and the surrounding areas became the most detailed mapped and best documented submarine areas of the Norwegian coast.

New marine surveys with mapping of the seafloor in coastal areas were initiated in 2016 at Southern Sunnmøre, covering the municipalities of Ulstein, Hareide, Sand and Vanylven. The maps provided new information of value for fisheries, aquaculture companies and other business and industrial enterprises, as well as for areal planners in the local and regional communities. The maps of the submarine environments were combined with new topographic data collected by the Norwegian Mapping Authority; and for the first time, maps covering areas from the shore to the deepest points of the seafloor were seamlessly combined.

The Southern Sunnmøre project was followed up with ‘Marine Base Maps for the Coastal Zone’, i.e. a new pilot project covering three coastal areas: Stavanger municipality in southwestern Norway, Ålesund-Giske in central Norway and Skjervøy-Kvænangen in northern Norway. With support from the national and local governments, the Norwegian Mapping Authority, NGU and the Institute of Marine Research (IMR) have developed 50 new maps and products, including comprehensive data on depth and seabed terrain, oceanographic data, geological maps of the seabed's physical and chemical properties, biology and observations of human impact, including pollution, trawl net marks and lost fishing gear (Fig. 12). Experience from the pilot areas has been very positive, and the three conducting national institutions hope to extend the marine base maps pilot to a national programme – a national mapping programme that will contribute to the strengthening of blue industries and will support the development of Norwegian coastal communities.

One important task resulting from the coastal mapping and Mareano programmes was the appointment of a marine working group to operationalize the criteria and use them to identify a selection of marine nature (‘nature units’) with the use of the Nature-in-Norway (NIN) System (NIN System version 2.2). The working group consisted of researchers from the Norwegian Institute for Water Research (NIVA), IMR and NGU. NiN is a common toolbox for describing nature in a standardized way. The systematic registration of nature types in Norway following the NIN system started in 2009, and a revised guide was published in 2016 (Halvorsen et al. 2016). NiN meets the needs of various sectors for a common conceptual apparatus, handles natural variation on all scales and can be adapted to many purposes, covering terrestrial, limnic and marine environments. With this approach, the system serves as a proper basis for mapping nature and nature types. NiN also provides a basis for work on red list assessment of geomorphological landscape types such as glaciers, delta plains and the Kvitskriuprestein, a group of scenic, slender natural pyramids formed in soil moraine masses by rain erosion found in Sel (Lindgaard and Henriksen 2011). Besides contributing to the development of the NiN system, NGU carried out geological mapping in Norwegian national parks, as in Rondane, from where a Quaternary geology map at scale 1:75 000 was published in 2014 (Follestad 2014). The printed map sheet also included descriptions and illustrations of landscapes and surficial deposits characteristic of the Rondane mountainous areas.

A portal with maps of ecological relevance called ‘Ecologic Base Map for Norway’ was launched in 2020. The main goal was to develop a more holistic nature diversity management system, where the ecological base map would combine existing maps of relevance for ecosystem management with new map layers showing the geodiversity in the actual areas. As initial contributions, NGU recently published two national map layers showing the distribution of carbonates and areas with enriched high-Fe–Mg. NGU is currently working on the development of several other maps with specific geological and mineralogical properties. In addition to mapping of national geotopes and red-listed landscape types, registration of geological heritage and geological sites of special interest for schools and the public has been carried out in different communities all over Norway (Fig. 14).

Traditionally, most Quaternary geology maps published by NGU have been produced at scales 1:20 000 and 1:50 000, although maps of some communities were published at different scales. In the years between 2010 and 2020, Quaternary maps at other scales were made available both as printed maps and as colour plots of different qualities (360 and 720 dpi). Examples are those of Lierne community at 1:100 000 (2017), Mjøsa Region at 1:125 000 (2017), Østfold County at 1:125 000 (2017), Rogaland County at 1:250 000 (2010) and Hedmark County at 1:300 000 (2017).

In 2021, an updated bedrock map covering the entire Norwegian mainland at scale 1:1 350 000 was published (Torgersen et al. 2021). In the years after the 2002 national bedrock compilation (Sigmond 2002), new land areas had been mapped at scale 1:50 000. In addition to a better areal coverage and more detailed field mapping, the 2021 map contains an updated legend of rock units. Given the long history of geological mapping, harmonizing legends (map units) across old map sheets is a major task. Through the history of geological mapping at NGU, application of uniform legends has been a matter of discussion, and the geologists carrying out the mapping of the long and mountainous country – with a 2562 km long border with Sweden, Finland and Russia – have had different and often somewhat conflicting views on which legends to use. Even today, artificial bedrock boundaries due to different use of legends are still common on the high resolution online digital maps.

In the present decade, the county programmes continued and came to include Trøndelag (completed in 2022) as well as Møre and Romsdal (started in 2022). New bedrock maps at scale 1:50 000 were produced, and an updated regional map covering Trøndelag at scale 1:400 000 was presented (Artsen and Gundleiksrud 2022) (Fig. 15). In addition to the classical display of the bedrock units with explanations, the map sheet also includes an overview of the compositions of different rock types and how they were formed. The Trøndelag mapping campaigns also covered airborne geophysics both onshore and offshore.

In 2022, the Geological Survey presented a new national plan for geological mapping of the land, coast and nearshore seabed. The plan provides a systematic overview of principles and criteria for which type of mapping and which geographical areas should be prioritized based on an overall socially beneficial perspective. Existing data at scale 1:50 000 are available in a production database and a script map database. The production database includes the maps that are only available in NGU's bedrock database, which now covers 60.7% (196 643 km²) of Norway's mainland and 52.5% including fjords and coastal areas.

In recent years, the Norwegian mainland and the remote island Jan Mayen in the North Atlantic have been mapped in detail by geologists from NGU (Fig. 16). In addition to conducting a major research programme on the island focusing on climatic variations and retreat of glaciers after the last glacial maximum (Lyså et al. 2021), Lyså et al. (2022) compiled a new Quaternary (surficial deposits) map at scale 1:50 000, covering the entire island. During the Norwegian Geomatics Day in 2022, the map of Jan Mayen received the People's Jury Prize to the best map. An even bigger achievement was the first prize received at the 31st International Cartographic Conference in Cape Town, South Africa in 2023.

Mapping of Svalbard and Norwegian territorial claims in Antarctica (Queen Maud Land and Peter I Island) has been carried out by the Norwegian Polar Institute. However, geologists from NGU have contributed to geological mapping and have been very active in geoscientific research programmes in both polar areas.

When Dr Hans H. Reusch (1852–1922) took over as Manager of NGU in 1888, he was given the clear instruction from the Ministry of the Interior that a main task for the Geological Survey is to ensure that the geological mapping and research would benefit business development (Ingvaldsen 1983; Børresen and Wale 2008). Throughout the history of the Geological Survey, this has been a main task but, the science and knowledge provided have also served several other societal needs. In our modern world, the need for more geoscience and higher quality geodata is constantly increasing, but the strategies to meet these growing needs and demands vary between national geological surveys. Many surveys follow the same strategic paths as NGU, keeping up the goals of being both ‘Practically useful and scientifically important’. Other surveys have outsourced science to academia, using part of their annual budget to support cooperation with universities and other scientific institutions, and some others have outsourced both geological mapping and science to external institutions. In his essay on geological mapping, Dewey (2023) writes that,

Most national geological surveys have shifted away from their initial purpose of making a detailed geological map of their country, to a useful and variety of other purposes such as contract work in hydrogeology, geo-engineering, geohazard, geochemical maps and consulting for smaller nations, to the detriment of national systematic mapping.

This is not the case at NGU in Norway, where geological mapping and management of national maps and databases still are its main tasks. Further, as a governmental institution, NGU is not allowed to carry out consulting and contract works in competition with private enterprises and companies.

As pointed out by Dewey (2023), the need for geological mapping will never end, and moving into the new millennium, the strategy of integrating geological mapping and science was kept well alive at NGU. The director at that time, Arne Bjørlykke, came from a position as Professor in Geology at the University of Oslo, and many of the geologists, geophysicists and geochemists at NGU have significant geoscientific records. In the next 2 decades, the survey participated in three National Centres of Excellence in Research (SFF) awarded by the Norwegian Research Council. These were the International Centre for Geohazards (ICG), Physics of Geological Processes (PGP) and the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE).

A question raised was if the scientific engagements drained much needed resources from basic mapping activities. This was a wrong assumption for two main reasons: (1) the research projects were basically financed by external funds provided by the Norwegian Research Council and the industry, (2) the research projects contributed new knowledge that enhanced the quality of mapping programmes.

Very often knowledge of regional geology is essential for solving geoscientific problems in the externally funded research projects, and the fact that regional geology and geological mapping are an important key for answering questions in geosciences (Meinhold et al. 2023) is well documented through the co-existence of NGU's geological maps and the publication series developed through the years. For ‘state geologists’ employed at NGU through the last 165 years, geological mapping and research have gone hand in hand.

An example: in the very first issue of the NGU's publication series, Reusch (1891) described scour marks from ice on the bedrock and moraine conglomerates (tillite) on the north side of Varangerfjorden in Finnmark, northernmost Norway (Fig. 17). Referring to works by the well-known geologists A. and J. Geikie, Reusch (1891) argued that the rocks, bedrock marks and deposits were much older than the last ice age, and could be of Cambro-Silurian age, as most of the Norwegian mountains. Later, the Bigganjarga tillite became known as a world-famous marker for the Cryogenian Marinoan glaciation (Varanger glaciation) (Henriksen et al. 2023) (Fig. 17). Today, NGU's main scientific publications series, NGU Bulletin, comprises 457 numbers, and the last issue contains an updated description of the geology of the Varanger Peninsula, including new geoscientific knowledge, revised regional geological interpretations, maps and pictures (Roberts and Siedlecka 2022) (Fig. 17). At NGU, integration of geological mapping and geoscientific research has been strengthened by international cooperation. One study that received much international attention was carried out by geoscientists from Australia, Canada, the UK, the USA and Norway, represented by Tor Grenne (NGU) (Fig. 18), presenting evidence for early life in Earth's oldest hydrothermal vents’ precipitates (Dodd et al. 2017).

International cooperation between geological surveys and different geoscientific institutions has also resulted in several new maps and services covering European regions and other parts of the world. Examples are maps and open access web portals such as EuroGeoSurveys (https://eurogeosurveys.org/research/our-experts/geological-mapping-and-modelling/), the Metallic Mineral Deposits Map of the Fennoscandian Shield (1:2 000 000) (Fig. 19) and the series of geological and geophysical maps of the circumpolar Arctic under the aegis of the CGMW (Petrov and Smelror 2015).

Today, NGU deals with a number of aspects related to the need for geological knowledge and information in society, including minerals, water and energy resources, land use and protection, engineering geology, geohazards, environmental and climatic changes, pollution and waste management, as well as education and geo-tourism. During its 165 years of existence, NGU has generated a substantial amount of information on the Earth's crust, its natural resources, its processes and the geological history of Norway, both onshore and offshore. Values are created and costs are saved when the knowledge presented on geological maps and databases become easily accessible to end-users in industry, government agencies, government institutes, public administrations, technical offices, academic and research institutes and private individuals (Smelror 2008, 2020). The development, operation and maintenance of national open access databases and maps of geological properties and processes are therefore key missions of NGU (https://www.ngu.no/geologiske-kart). From the NGU's databases, users can extract fundamental data and processed information that will help them to carry out their tasks, regardless of whether they operate within the mineral industry, the consultancy sector, the public administration or in research and education. As mentioned above, this mission is shared among several federal agencies in Norway through the Norge Digital programme and the Geonorge web services.

Norge Digital is a collaboration between institutions that are responsible for providing regional and location-based information and/or that are major users of such information. These include municipalities, counties and national agencies that are suppliers and users of geographic data and online services. There are joint technical and administrative obligations and requirements in the collaboration. The development of the collaboration is anchored in the Geodata Act and related regulations (https://www.geonorge.no/en/infrastructure/norway-digital/spatial-data-infrastructure/). The web service Geonorge (www.geonorge.no) is a collaboration between public enterprises responsible for establishing and managing map data and other location-based information. The service is developed and operated by the Norwegian Mapping Authority, and NGU contributes with the delivery of geological datasets and services. As of 2023, there are close to 7500 metadata descriptions for datasets, APIs and map viewing solutions on Geonorge.

The first geological app for mobile phones was made available in 2012. Today, the open access digital map services include maps of bedrock, surficial deposits, marine geology (seabed maps), marine limit and the potential for marine clay deposits, mineral resources, groundwater, geochemistry, radon risk, geophysics (including a geoscience portal), unstable rock slopes, subsidence and unstable slopes (InSAR Norway), underground investigations (boreholes and data; the national database for investigations of the underground, Norwegian: Nasjonal Database for Grunnundersøkelser – NADAG), permafrost (mainland and Svalbard), geological heritage, geological sites of special interest (Norwegian: Geosteder i Norge og Sverige – GNIST) and a portal providing users with an overview of the geology in their community (https://www.ngu.no/geologiske-kart). The past 2 decades, the use of digital map applications and downloads from NGU's map services have increased steadily and significantly. When the first digital maps were presented online, almost 2 decades ago, only a handful of weekly users were registered. Today, the number of users is between 20 000 and 30 000 per week through www.geonorge.no and/or www.ngu.no. In 2022, most visits and downloads were from the National Bedrock Database, followed by radon risk and underground investigations (NADAG). Making the geological maps and databases accessible and readable to planners and developers with limited geological knowledge has significantly increased the number of users, whereby raising the ‘practical usefulness’ of the geological information.

The introduction quote ‘If a picture is worth a thousand words, then a geological map is worth a million’ should be widened to also include geological data as such. With reference to the NGU's NADAG database, Vista Analyse has calculated that this national database of basic underground surveys and drilling reports (http://geo.ngu.no/kart/nadag/) – which has an annual cost of 2.5 million NOK – translates into annual savings of at least 16 million NOK. As for maps, money is saved through the reuse of information, reduced time to obtain information, reduced planning time, better plans and less expensive development projects, as well as better preparedness and handling in the event of natural hazards.

During its 165 years of existence, NGU has generated a substantial amount of information on the Norwegian crust, its natural resources, its processes and the geological history of Norway, both onshore and offshore. Mapping and collecting geological knowledge and making data and maps freely available as a public good is very profitable for society. Values are created and costs are saved when the knowledge presented on geological maps and databases become easily accessible to end-users in the industry, government agencies, government institutes, public administrations, technical offices, academic and research institutes, as well as private individuals. Through the past 165 years, the maps and associated descriptions have answered to the main ambitions presented to the government along with the proposal to create a Geological Survey in Norway in 1858: to be of economic (‘practically useful’), scientific (‘important’) and cultural (‘honourable to country’) value. Geological maps and linked data are particularly useful when they are accessible in standardized digital formats and through online open public access. Develop, operate and maintain open access national databases and maps of geological properties and processes are therefore key missions of NGU. According to the Chinese philosopher and reformer Confucius (551–479 BC), ‘the essence of knowledge is to have it and to apply it’. We believe it is essential also to share it.

We should all acknowledge the valuable contributions from all those who have spent time of their lives mapping the geology of Norway; and those who have contributed to make knowledge available on maps, in reports and databases and through web portals and services publicly available to everyone. Thanks are due to Hugh N. Rice and Graham Leslie for their constructive and helpful reviews of this contribution.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

MS: writing – review & editing (lead).

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.