Erik Sturkell

University of Gothenburg | GU · Department of Earth Sciences

An advance has been made towards a method for forecasting earthquakes several months before they occur. The method relies on changes of groundwater chemistry as earthquake precursors. In a study published in 2014, we showed that changes of groundwater chemistry occurred prior to and were associated with two earthquakes of magnitude 5 and higher, wh...

Unrest began in July 2021 at Askja volcano in the Northern Volcanic Zone (NVZ) of Iceland. Its most recent eruption, in 1961, was predominantly effusive and produced ∼0.1 km³ lava field. The last plinian eruption at Askja occurred in 1875. Geodetic measurements between 1983 and 2021 detail subsidence of Askja, decaying in an exponential manner. At...

Recent interest in microplastic pollution of natural environments has brought forth samples which confirm the pollutant’s omnipresence in a variety of ecosystems. This includes locations furthest removed from human activity. Atmospheric transport and deposition are suspected as the primary transport pathway to these remote locations. The factors mo...

Very few impact craters on Earth have preserved proximal ejecta (ejecta blanket), which when present help us to better understand the cratering processes when asteroid hits Earth. The 458 Ma old Lockne impact structure consists of a 7.5‐km wide nested crater in the crystalline basement surrounded by an approximately 3‐km wide brim developed in the...

The Rochechouart impact structure, located in the western part of the Massif Central in France, has been suggested to be one of the largest impact structures in western Europe. Various age datings have placed the event in a span from the Late Triassic to the Early Jurassic, but the most recent works favour a Late Triassic age. Very little is known...

The submarine tufa columns of Ikka Fjord in Southwest Greenland have been studied during multiple field campaigns since 1995. The fjord contains close to thousand columns previously shown to consist of the metastable carbonate mineral ikaite (CaCO3·6H2O), which requires near-freezing conditions to remain stable over longer periods of time. During a...

Ikka Fjord in SW Greenland is world famous for its submarine, cold-water craving ikaite (CaCO3·6H2O) tufa columns. Due to the uniqueness of the columns, Ikka Fjord is declared a protected area by the Greenlandic authorities. In the summers of 2018–19, multibeam sonar bathymetry and aerial drone photogrammetric surveys were made in Ikka Fjord mappin...

We present repeated radio-echo sounding (RES, 5 MHz) on a profile grid over the eastern Skaftá cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is a ∼ 3 km wide and 50–150 m deep ice cauldron created and maintained by subglacial geothermal activity of ∼ 1 GW. Beneath the cauldron and 200–400 m thick ice, water accumulates in a subglacial lak...

We present repeated radio-echo sounding (RES, 5 MHz) on a profile grid over the Eastern Skaftá Cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is ~3 km wide and 50–150 m deep ice cauldron created and maintained by subglacial geothermal activity of ~1 GW. Beneath the cauldron and 200–400 m thick ice, water accumulates in a lake and is releas...

The intensive scientific studies of the unique submarine mineral columns in Ikka Fjord began in 1995 and involved biological, geological and geophysical programmes of research. The columns were identified to consist entirely of the cold-water mineral, ikaite (CaCO3·6H2O), which is only stable below 6°C. A total of 678 columns in the height of 1-20...

Hundreds of tufa columns composed of ikaite (CaCO3 · 6H2O) stand at the bottom of Ikka Fjord in SW Greenland. Why these cold water tufa columns form only at this site is not known. Nepheline-syenite and carbonatite rocks, part of the Grønnedal-Ika igneous complex, surround the fjord and an association with the columns has been suggested. Sodium-car...

The mineral ikaite (CaCO 3 · 6H 2 O) was first discovered as tufa columns in Ikka Fjord, southwest Greenland 1,2. More than 700 columns stand at the bottom of this fjord. Why these columns form only at this site is unknown. Nepheline-syenite and carbonatite rocks surround the fjord and an association with the columns has been suggested 2. Here we i...

The marine Ikka Fjord in southwest Greenland is famous for its remarkable and unique submarine columns made of the cold-carbonate ikaite (CaCO3·6H2O). Here, natural processes lead to fast-precipitating ikaite at low temperatures (< 6°C) when carbonate-bearing groundwater seeps through fractures in the seabed of Ikka Fjord and mixes with seawater. W...

Two boreholes in North Iceland have been monitored for groundwater changes on a weekly basis since 2002 and 2008, respectively. One borehole, HU-01 is located close to the town of Húsavík, whereas the other borehole, HA-01 is located close to the school in Hafralækur. The long time series thus obtained have provided a unique data set that has shown...

Hydrochemical changes before and after earthquakes have been reported for over 50 years. However, few reports provide sufficient data for an association to be verified statistically. Also, no mechanism has been proposed to explain why hydrochemical changes are observed far from earthquake foci where associated strains are small (<10⁻⁸). Here we add...

The mineral ikaite (CaCO3·6H2O) precipitates from a mixture of spring water and seawater as tufa columns which grow at a rate of up to 50 cm per year reaching heights of up to 18 m in Ikka Fjord, SW Greenland. In the fjord, column formation occurs only at the base of a nepheline syenite‑carbonatite complex that flanks the fjord and an association h...

Drill core petrography from the Rochechouart impact structure.

Geologiskt forum nr. 100: Under vattenytan i Ikkafjorden på Grönland gömmer sig ett stort antal mystiska pelare av mineralet ikait. Dessa pelare är till och med omnämnda i sagor som härstammar från vikingatiden. Följ med på en resa både under och ovanför vattenytan för att förstå hur dessa pelare bildades och varför.

Petrogenetic studies of carbonatites are challenging because carbonatite mineral assemblages and mineral chemistry typically reflect both variable pressure-temperature conditions during crystallization and fluid-rock interaction caused by magmatic-hydrothermal fluids. However, this complexity results in recognizable alteration textures and trace el...

Groundwater monitoring in North Iceland near the municipality Hafralækur has been ongoing since September 2008 by sampling of water on a weekly basis from borehole, HA-01. The motivation for carrying out this monitoring is the borehole’s proximity to the Húsavík-Flatey Fault (HFF), which runs across the Tjörnes peninsula. The HFF and the Grímsey Li...

The marine Ikka Fjord in Greenland is well known for its remarkable submarine columns made of the cold-carbonate ikaite (CaCO3ꞏ6H2O). Here, natural processes lead to fast-precipitating ikaite at low temperatures (< 10°C) when carbonate-bearing groundwater seeps through fractures in Ikka Fjord and mixes with seawater. Within an area of 0.75 km2, 678...

När vi reste till Australien i oktober 2017, vår första vistelse i den delen av världen, hade vi uppfattningen att vi kom till en gammal kraton där man kan finna de äldsta zirkonerna och där den magmatiska aktiviteten är obefintlig. Det första vi gjorde var att besöka området kring Mt. Macedon med Hanging Rock i delstaten Victoria och vandra i de n...

The hydrated carbonate mineral ikaite (CaCO3 · 6H2O) is thermodynamically unstable at all known conditions on Earth. Despite this, ikaite has been found in marine sediments, as tufa columns and in sea ice. The reason for these occurrences remains unknown. However, cold temperatures (<6 °C), high pH and the presence of Mg2+ and SO42- in these settin...

Målingen is the 0.7 km wide minor crater associated to the 10 times larger Lockne crater in the unique Lockne–Målingen doublet. The craters formed at 458 Ma by the impact of a binary asteroid related to the well‐known 470 Ma Main Belt breakup event responsible for a large number of Ordovician craters and fossil meteorites. The binary asteroid struc...

Geologiskt forum nr. 97 2018, 4-5. Efter ett systematiskt arbete har vi nu en bra överblick om geologen i filmer – men hur många geologer finns avbildade på sedlar? Under en resa på världens undersida besökte vi ett fantastiskt museum i Hobart som uppmärksammade en australisk polarexpedition 1911–1914. Expeditions ledaren var geolog och han har hed...

Geologiskt forum nr. 97 2018, 20-24. I samband med en vulkanologisk konferens i Portland i USA hade jag förmånen att få delta i en exkursion till Mount St Helens som inkluderade en 8 km lång vandring i området. Exkursionen leddes av geologer och geofysiker från Cascades Volcano Observatory som tillhör USGS. Texten om vulkanen bygger på material frå...

First results from the Rochechouart impact crater drilling campaign.

Dating of the Grønnedal-Íka igneous complex in Southwest Greenland is important to understand the continental rifting event – the Gardar episode. In this study, three different methods have been applied to rock specimens and previously published data to better constrain the age of the complex: a) U-Pb dating of zircons extracted from hand specimens...

Petrogenetic studies of carbonatites – carbonate-dominated igneous rocks – are challenging because carbonatite mineral assemblages and mineral chemistry typically reflect variable pressure-temperature conditions during crystallization, and fluid-rock interaction caused by magmatic-hydrothermal fluids. However, this complexity results in recognizabl...

Sommaren 2014 inledde svenska och danska geologer ett nytt forskningsprojekt i en av Grönlands geologiska skattkammare. Detta inriktades mot Gardarintrusionens bergarter i sydvästra Grönland och speciellt Grønnedal-Íka-karbonatiten och nefelinsyeniten nära flottbasen Grønnedal. Dessutom företogs flera besök till kryolitförekomsten i den närliggande...

In a narrow fjord in southwest Greenland, impressive columns composed of the rare mineral ikaite (CaCO 3 ·6H 2 O) are forming and can grow up to 0.5 m/year. They form from a mixture of seawater and carbonate rich spring water high in pH emanating from underlying alkaline magmatic rocks at the bottom of the fjord. Why metastable ikaite forms instead...

Located on the mid-Atlantic ridge, Iceland allows for direct measurement of crustal deformation. Global Positioning System (GPS) data from the Eastern Volcanic Zone (EVZ), Iceland, and crustal deformation of the rift near its southern end at 64°N show a spreading rate of 13.8 ± 1.8 mm yr− 1. About 90% of the deformation occurs in an 80 to 90-km wid...

GPS measurements spanning 2008 to 2014 are used to derive the surface velocity field across the Northern Volcanic Zone (NVZ) of Iceland, a subaerial part of the divergent boundary between the North-American and Eurasian plates. No volcanic activity nor magmatic intrusions were detected in the zone during this time-period. We infer an extensional ra...

The local geology at Kloxåsen is characterised by ejecta deposits from the 458 Ma Lockne marine impact. The Kloxåsen ejecta are located on a Caledonian parautochthonous unit, approximately 7 km from the centre of the 7.5-km-wide Lockne crater structure. The ejecta were deposited on the seafloor and were covered with seawater immediately after the i...

Geologen på film – vilka egenskaper har hon eller han egentligen? Här presenteras en uppföljning av undersökningen om filmgeologer från 2013. Fler filmer med geologer har hittats. Har bilden blivit en annan eller består resultatet?

The Mid Atlantic Ridge (MAR), the divergent boundary between the North American and Eurasian plates, is exposed on Iceland, with relative plate spreading rate of ~19 mm/yr. Modeling studies of the divergence in north and south Iceland, including the study of postrifting relaxation, have fit geodetic data well using elastic half-space and finite ele...

The Surtsey Island was built from the seafloor at 130 m depth during the period 1963–1967. Two tephra cones formed above the sea level up to a height of 170 m. They were later partly covered by a lava shield when the magma conduit became isolated from the seawater and the activity changed into lava effusion. The final volume of Surtsey was 0.8 km3...

Since October 2008, groundwater samples have been collected on a weekly basis from a bore hole (HA-01), which is situated near Hafralækur, approximately 30 km south of Húsavík. This bore hole taps a series of aquifers, which are at approximate depths ranging from 65 to 100 m. The water has a low content of dissolved solids (240 ppm), which is typic...

Studying the use of stone over time gives in-sight into the development of architecture and infrastructure alike. A study of just over 2000 buildings in central Gothenburg found that 1224 buildings dating from 1800–1944 have stone plinths. Thereafter concrete became the predominant material. The prevalence of stone in buildings varies over time, th...

The origin of Dimmuborgir, a shield-like volcanic structure within the Younger Laxá lava flow field near Lake Mývatn, in northern Iceland, has long been questioned. New airborne laser mapping (light detection and ranging (LiDAR)), combined with ground-penetrating radar results and a detailed field study, suggests that Dimmuborgir is a complex of at...

Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northern Iceland from October 2008 to June 2015 revealed 1) a long-term decrease in concentration of Si and Na and 2) an abrupt increase in concentration of Na before each of two consecutive M > 5 earthquakes which occurred in 2012 and 2013, both 76 km from Hafralækur...

North America-Eurasia relative plate motion across the Mid-Atlantic Ridge in south Iceland is partitioned between overlapping ridge segments, the Western Volcanic Zone (WVZ) and the Eastern Volcanic Zone. The Thingvellir graben, a 4.7km wide graben, lies along the central axis of the WVZ and has subsided >35m during the Holocene. An ~8km long level...

The 1300 Ma Grønnedal-Íka igneous complex in southwest Greenland comprises nepheline syenites and carbonatites. It belongs to a suite of intrusions formed 1300-1100 Ma ago referred to as the Gardar period. In modern time (the last ca. 8000 years), fluid-rock interactions involving the nepheline syenites and carbonatites gives rise to about one thou...

Chemical changes in groundwater before and after earthquakes have been compared with analyses of drill cuttings taken from a borehole in northern Iceland. Groundwater samples were taken on a weekly basis from September 2008 to June 2015 from a 100 m deep borehole at Hafralækur which is situated in the seismically-active Tjörnes Fracture Zone (TFZ),...

För 470 millioner år sedan inträffade en av de största kosmiska kollisioner som skett i solsystemet sedan planeterna bildades. En cirka 200 kilometer stor asteroid, i asteroidbältet mellan Mars och Jupiter, krossades i miljontals bitar varav många fick banor som kom att korsa jordens.

Geodynamic process as advection-convection of the Mid-Atlantic Ocean Ridge (MAR), that is exposed on land in Iceland is investigated. Advection is considered for the plate spreading velocity. Geodetic GPS data during 2000-2010 is used to estimate plate spreading velocity along a profile in the Eastern Volcanic Zone (EVZ), Iceland striking N102˚E, a...

When geologists gather for a beer after work or around a campfire after a long day in the field, the conversation sometimes turns to how our profession is portrayed on film. Are geologists heroes or villains? Do they appear only in supporting roles – their parts limited to entering an office, uttering "Drill here," and promptly leaving the scene –...

Gravity and magnetic surveys were conducted in a 4 x 4 km2 area in the Hackås Municipality, Jämtland County, central Sweden. The fieldwork took place in three successive summer field campaigns 2010-12. The target for the surveys was a suspected impact structure centered at Målingen, a crescent shaped bay in the larger Lake Näkten (Ormö et al. 2014a...

Analysis of a time series of ground deformation measurements at active volcanoes can provide an improved understanding of sub-volcanic and sub-aerial processes; including those related to magmatic, hydrothermal and structural development. Interpreting a long time series may also help determine background behavior, and identify any deviations from t...

The overall objective of the presented study is to explore the impact of groundwater fluctuations on greenhouse gas (GHG) emissions from peatlands and in particular from drained organic soils. The hypothesis is that drained organic soils react sensitively to changing water content, i.e. that frequent changes of groundwater level enhance the emissio...

Several studies of meteorites show that a large disruption of an asteroid occurred ca. 470 Ma in our solar system's asteroid belt. As a consequence, a large number of meteorite impacts occurred on Earth during the following few million years. The finding and characterization, for the first time, of planar deformation features in quartz grains from...

Ön Hawai’i har mycket för alla och speciellt för geologer: aktiva vulkaner, lavalandskap, vackra stränder och paraplydrinkar, men inga metamorfa bergarter (förutom i bardiskar). Vill du studera basalter så ligger Island mycket närmare, men om du önskar att ha det lite varmare och dessutom vill skåda en frodig växlighet ovan basalten – då är Hawai’i...

Introduction: The Hummeln structure (57°22'N, 16°15'E) is located in the Småland province, in south-ern Sweden. It consists of an over 160 m deep and 1.2 km wide depression in the Precambrian crystalline basement, within Lake Hummeln. The origin of the circular depression has puzzled the geological commu-nity for nearly 200 years (see below). Here...

Crust at many divergent plate boundaries forms primarily by the injection of vertical sheet-like dykes, some tens of kilometres long1. Previous models of rifting events indicate either lateral dyke growth away from a feeding source, with propagation rates decreasing as the dyke lengthens2, 3, 4, or magma flowing vertically into dykes from an underl...

Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering ra...

Supplementary Table 1

Groundwater chemistry has been observed to change before earthquakes and is proposed as a precursor signal. Such changes include variations in radon count rates1,2, concentrations of dissolved elements3–5 and stable isotope ratios4,5. Changes in seismicwave velocities6,water levels in boreholes7, micro-seismicity8 and shear wave splitting9 are also...

Based on hydrochemical monitoring, petrological observations and geochemical modelling, we identify a mechanism and estimate a timescale for fault healing after an earthquake. Hydrochemical monitoring of groundwater samples from an aquifer, which is at an approximate depth of 1200 meters, was conducted over a period of ten years. Groundwater sample...

Grímsvötn Volcano is the most active volcano in Iceland, and its last three eruptions were in 1998, 2004 and 2011. Here we analyze the displacement around Grímsvötn during these last three eruptive cycles using 10 GPS stations. The observed displacements in this region generally contain a linear component of tectonic and glacio-isostatic origin, in...

Iceland is located on the mid Atlantic ridge, where the spreading rate is nearly 2 cm/yr. The high rate of mag-matism in Iceland is caused by the interaction between the Iceland hotspot and the divergent mid-Atlantic plate boundary. Iceland hosts about 35 volcanoes or volcanic systems that are active. Most of these are aliened along the plate bound...

Iceland is a subaerial part of the Mid-Atlantic Ridge, where the divergent plate boundary between the North- American and Eurasian Plates can be studied. The Northern Volcanic Zone (NVZ) of Iceland, comprised of several volcanic systems, is particularly well suited to study interplay between volcanoes, geothermal areas and plate spreading, as the z...

The Målingen structure in Sweden has for a long time been suspected to be the result of an impact; however, no hard evidence, i.e., shock metamorphic features or traces of the impactor, has so far been presented. Here we show that quartz grains displaying planar deformation features (PDFs) oriented along crystallographic planes typical for shock me...

The Målingen structure is an approximately 700 m wide, rimmed, sediment-filled, circular depression in Precambrian crystalline basement approximately 16.2 km from the concentric, marine-target Lockne crater (inner, basement crater diameter approximately 7.5 km, total diameter in sedimentary strata approximately 13.5 km). We present here results fro...

Of the few known putative doublets on Earth, the Lockne and Målingen craters are the first to be dated with enough precision to be considered unequivocal.

Magma flow during volcanic eruptions causes surface deformation that can be used to constrain the location, geometry and internal pressure evolution of the underlying magmatic source1. The height of the volcanic plumes during explosive eruptions also varies with magma flow rate, in a nonlinear way2,3. In May 2011, an explosive eruption at Grímsvötn...

The Concentric Impact Structure Project (CISP) focuses on the two best-known craters on the Scandinavian Peninsula - Siljan and Lockne. They are primary models for concentric impact structures, i.e. craters with a shallow, outer crater developed in a weaker/less dense upper layer surrounding a deeper crater in the crystalline basement. The effects...

Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidenc...