1. Using geophysical data for an intercorrelated study of marine Ikka Fjord and the Grønnedal-Íka alkaline complex, SW Greenland
The 1325±6 Ma intrusive complex of Grønnedal-Íka in SW Greenland comprises rocks of mainly nephelines syenites and carbonatites associated with continental rifting during the Gardar rifting episode at 1.3–1.1 Ga. This complex intruded into approximately 2.7 Ga gneissic rocks at a shallow depth. Later uplift, faulting and erosion have deformed the complex to its current elongated shape of c. 8 x 3 km. It forms the 500 m tall mountains on the northern shore of the inner part of the marine Ikka Fjord, and is also found along its southern shore. Thus, the bedrock underlying inner Ikka Fjord most likely consists of nepheline syenites. In direct correlation to the outcrops of the Grønnedal-Íka complex, close to a thousand submarine columns built up by the mineral ikaite (CaCO3Ÿ6H2O) are found growing over groundwater springs issuing from the bottom of the fjord. The theory is that groundwater percolating through the old and fractured Grønnedal-Íka complex dissolves minerals that lead to a sodium carbonate-enriched fluid seeping up through fractures in the seabed. When this fluid mixes with seawater, ikaite precipitates and grows upwards as the groundwater fluid has a lower density than seawater. The tallest columns grow up to 18-20 m to a few meters below sea surface, most likely limited by the ice coverage during wintertime and by a fresh water layer at the top of the water column. Ikka Fjord is the only place on Earth where these ikaite columns are found.
During fieldwork in 2018, a network of survey control points was established and drone-acquired aerial photographs of Ikka Fjord were collected at low tide, when the columns are visible. These data will be used for the design of a multibeam echosounder survey to be carried out in Ikka Fjord in June 2019 with the purpose of mapping the columns, subsurface fractures, and bedrock exposures on the fjord-bed in accurate detail. In addition, a sub-bottom profiler and further drone surveys are planed to supplement the data from 2018. We are looking for a candidate with a background in marine geophysics, who can work on the data collected both in 2018 and 2019. The successful candidate will take part in the fieldwork to Ikka Fjord in June 2019.
NordVulk collaborator: Gabrielle Stockmann
Nordic collaborator: Erik Sturkell, Professor in Applied Geophysics, University of Gothenburg, Sweden
Other collaborators: Paul Seaman, independent geophysicist, UK, and Halldór Geirsson, geophysicist at the University of Iceland
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2. Supercritical fluids around magmatic intrusions
Volcanic geothermal systems are generally associated with magmatic intrusions in the upper crust resulting in increased fluid temperature and convection of the groundwater systems. Recent modelling suggests that supercritical fluids with temperatures of >400°C exists in the roots of active geothermal systems. More than 25 deep wells drilled in geothermal fields worldwide have encountered supercritical fluids and in some cases magma. The origin and geochemistry of the fluids is at present poorly constrained. In the project we aim at addressing the question: what is the origin and chemical composition of such supercritical fluids? State-of-the-art isotope and geochemical approaches will be applied including volatile chemistry (H, O, B, Cl, Si, C) and isotope geothermometry (δD, δ18O, δ13C isotope ratios for H2O, H2, CO2, CH4) and the methods used to target potential supercritical fluid reservoirs at the Hengill volcanic system (SW Iceland) in relation to the IDDP-3 well and the IDDP-project.
NordVulk collaborator: Andri Stefánsson
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3. Petrography and geochemistry of hydrothermally altered drill cores from Hoffell, Southeast Iceland
Southeast Iceland has experienced more erosion than other parts of Iceland, leading to exposures of volcanic rocks and intrusions from greater depths than elsewhere in the country. Hoffell is in this area near the edge of Vatnajökull glacier, where erosion has removed over 2000 meters of overburden and exposed highly altered rocks in the lower greenschist facies at the flanks of Geitafell central volcano. A number of background studies are available from the field, several PhD and MSc studies, and most recently a mineralogical study within the EU-FP7 supported IMAGE project. As a part of an exploration effort to find hot water for domestic use, a number of wells have been drilled in the vicinity of Hoffell farmhouse, including two where 102 m and 140 m of drill cores were recovered. The cores are exceptionally continuous, but have not been properly studied. They show well-developed structural and mineralogical features, including secondary mineral assemblages of greenschist facies alteration, and possibly some contact metamorphism, and superimposition of zeolite facies mineralogy. The successful applicant is expected to perform a detailed petrographic study of the cores and do some geochemical analyses, an appealing and challenging study for an interested researcher. In addition to facilities provided at the University of Iceland, the applicant will have access to the drill core research lab at the Reykjanes geothermal power plant. This study is especially timely in light of the recent successful drilling of a 4.65 km deep geothermal well into amphibolite grade rocks at Reykjanes by the IDDP consortium.
NordVulk collaborators: Enikő Bali and Guðmundur H. Guðfinnsson
Nordic collaborators: Guðmundur Ómar Friðleifsson at HS Orka, Iceland and Magnús Ólafsson at Iceland GeoSurvey, Iceland.
4. Constraining post-glacial eruption rates of Icelandic lavas using palaeomagnetic secular variation
The post-glacial volcanism of Iceland is dominated by mafic effusive eruptions, with ~500 lavas emplaced over the past 11,000 years. The ages of the majority of these lavas are poorly constrained or unknown and this hinders our understanding of postglacial eruption rates. Although radiocarbon or other isotopic dating methods have been applied to Icelandic lavas, they are not appropriate in all cases and they are additionally time consuming and expensive. An alternative approach is to use palaeomagnetic dating. As lavas cool the magnetic moments of the iron oxides within them align with the direction of Earth’s magnetic field and acquire a moment (intensity) that is proportional to the strength of the field. Earth’s magnetic field varies in both direction and strength on timescales of centuries to millennia and these variations can be recorded by lavas. By determining the directions and intensities recorded by lavas of unknown ages and matching them to temporally continuous reference curves, the ages of the lavas can be estimated. However, the first step in this process is to develop reliable reference curves of direction and intensity for Iceland. This one year post-doc project focusses on obtaining new palaeodirectional and palaeointensity data from lavas that have good age control, with the overall aim of developing the first palaeomagnetic reference curve for Iceland.
This project will be primarily conducted at the Institute of Earth Sciences, University of Iceland, with the majority of palaeodirectional and palaeointensity analyses being made in the institute’s newly refurbished palaeomagnetism laboratory. More detailed rock magnetic analyses will be performed during visits to the palaeomagnetic laboratory in Lund, Sweden. Additional palaeointensity experiments using the microwave method will be made by the post-doc during a visit to the University of Liverpool Geomagnetism Laboratory.
NordVulk collaborator: Maxwell Brown and Þorvaldur Þórðarson
Nordic collaborator: Andreas Nilsson, Lund University, Sweden
Other collaborators: Mimi Hill, University of Liverpool, UK
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5. Control of repose time before Hekla eruptions on the magmatic activity
Prediction of future activity of a given volcano relies upon thorough knowledge of its past activity. Historical eruptions of Mt. Hekla volcano are relatively well known from the pioneering study of late Sigurdur Thorarinsson and following researchers. The length and intensity of the initial explosive phase is proportional to the foregoing repose time. The same holds for the SiO2 concentrations of the first formed tephra most likely due to enhanced time of magma differentiation. However, the relationships with repose time are only established for the last five centuries. Moreover, how the magma evolution is reflected in the mineral compositions has not yet been studied in detail. We propose to extend the time scale for possible repose time controlled parameters (composition, volume of tephra etc.) for the remaining historical activity of Hekla and possibly into the prehistoric period. Additionally, the project aims at examining the mineralogical evolution and associated volatile composition through detailed studies of mineral and melt inclusions compositions from the 1947 tephra, which was produced after one of the longest repose times at Hekla. The results should lead to better understanding of how fast magma differentiates and builds up excess volatile concentrations before explosive eruptions.
NordVulk collaborators: Olgeir Sigmarsson, Maria Helen Janebo and Gudrun Larsen
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6. Tephra stratigraphy in Svalbard – Distal deposition of Icelandic tephra
The aim of the project is to investigate distal deposition of Icelandic tephra (cryptotephra) in the high-Arctic by constructing a tephra stratigraphical framework using a collection of Holocene lake sediments from Svalbard. Information on distal distribution of Icelandic tephra in the high-Arctic is sparse. Therefore, a tephra stratigraphical framework from Svalbard will be an important contribution to the knowledge on explosive volcanism in the North Atlantic region and will provide a more comprehensive record on tephra distribution extent and pathways. Tephra investigation in the lake sediments from Svalbard has the potential to answer questions such as:
* Which volcanoes/volcanic provenances were the key players in tephra deposition on Svalbard during the Holocene?
* How frequent was the tephra deposition?
* Is there evidence of volcanism/tephra from other volcanic provenances than Iceland, such as Jan Mayen, the Aleutian arch or Kamchatka?
Information on distal distribution of tephra is important for understanding explosive volcanic processes, events and behavior of volcanoes as well as being of significant value for volcanic risk assessment and hazard modeling.
Furthermore, such a tephra stratigraphical study has the potential to provide a chronological framework for paleoclimatological archives in the Arctic.
Nordvulk collaborators: Esther Ruth Guðmundsdóttir and Ólafur Ingólfsson
Nordic collaborators: Anders Schomacker, UiT The Arctic University of Norway
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7. Graben subsidence in western Öxarfjörður
Graben subsidence often occurs as a result of shallow dike intrusions, such as the one from Bárðarbunga in 2014. However, it is unclear whether that is always the case, or whether some grabens form amagmatically.
The main aim of this project is to study the fault offsets in Öxarfjörður by using 3D bathymetric data and chirp seismic reflection data, both of which have already been acquired. The data will be processed using GIS applications. The characteristics of the faults and the accompanying graben structures will be studied and compared with grabens formed in rifting events on land in order to see whether they share similar characteristics.
NordVulk collaborators: Ásta Rut Hjartardóttir, Bryndís Brandsdóttir and Páll Einarsson
8. The southern Hofsjökull fissure swarms
Generally, fissure swarms emerge from central volcanoes approximately perpendicular to the plate spreading vector. The Hofsjökull volcanic system possesses three fissure swarms that emerge south of the Hofsjökull central volcano, instead of one as is commonly the case. The fissure swarms also seem to be influenced by the silicic Kerlingafjöll rhyolitic complex which is located south of Hofsjökull. This is therefore a rather unusual situation, but one which has not been studied in detail. In this project the southern fissure swarms will be mapped, both by using aerial photographs and by using detailed digital elevation models (DEMs). Field work will also be conducted to study the fractures and grabens on ground. The aim is to study the characteristics of these fissure swarms, their relationship with Kerlingafjöll, and how far the fissure swarms propagate into the Hreppar microplate.
NordVulk collaborators: Ásta Rut Hjartardóttir and Páll Einarsson
9. Volcanic influences on atmospheric circulation and climate in the North Atlantic region
Volcanic aerosols from explosive eruptions reach the lower stratosphere. Here they scatter and absorb sunlight and cool the earths surface. The direct effect of a single eruption can last of to 2-3 years. However, stratospheric volcanic aerosols also affect atmospheric circulation via changes in the meridional temperature gradient. This can have longer lasting effects due to atmosphere-ocean interaction. Sjolte et al. (2018) showed that strong equatorial eruptions of the past 800 years could have had persistent impacts of up to 5 years after the eruption by forcing the North Atlantic Oscillation (NAO) to a positive state during winter. Long lasting effects could also exist for high latitude eruptions, by forcing the NAO to a negative state (Guðlaugsdóttir et al., 2018). Sjolte is currently working on expanding the climate reconstruction used in Sjolte et al. (2018) to include summer and annual data. Furthermore, there are plans to extend these reconstructions with a larger network of climate proxy data in order to better constrain the past variability. In this NordVulk collaboration I suggest to: · Use reconstructions of seasonal climate and atmospheric circulation in the North Atlantic region (Sjolte et al., in prep.) to analyze the impact of equatorial and high latitude eruptions · Synthesize the reconstructed climate response with historical documentation of societal impact of volcanic eruptions such as crop yields, famine and drought. The NordVulk fellow would both work on the analysis of the climate signal in the reconstructions and the synthesis with historical documentation. The latter would be done in collaboration with historians and other experts on the topic.
NordVulk collaborator: Árný E. Sveinbjörnsdóttir
Nordic collaborator: Jesper Sjolte, Researcher Dept. Geology, Lund University, Sweden
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10. Chemical and magnetic signatures of iron in Icelandic tephra
Tephras are an important soil parent material in volcanic regions and contribute to rapid cycling of metals such as Al and Fe in terrestrial environments. It is generally understood that tephra weathers quickly to produce high concentrations of poorly crystalline Fe-oxides and Al-Si clays. However, the distribution and relative mobility of Fe in unweathered tephra and its influence on soil iron fractions in Iceland has not been quantified.
The aim of this project is to determine the speciation of iron in various Icelandic tephras based on chemical extractions. In particular, the proportion of labile Fe and Al will be investigated, as this fraction is likely to quickly weather out and form secondary soil minerals. These results will enable much improved estimates of secondary mineral content to be made for Icelandic soils, so that soil mineralogy can be better used as an indicator of relative soil development. Magnetic characterization will also be used to identify microcrystalline Fe-oxide phases in tephra and to evaluate the use of rock magnetic properties for tephra discrimination. Chemical and magnetic properties of Fe in Icelandic tephras will be compared across eruptions of different age and composition.
NordVulk collaborators: Jessica Till and Maria Janebo
11. Slope stability analysis on the Svínafellsheiði mountain side in SE Iceland
Since the end of the Little Ice Age (LIA) glaciers have retreated in alpine and high mountain environments worldwide. This warming trend has been detected in Iceland and has caused significant changes on and around the present day outlet glaciers, causing them both to retreat and thin, with accelerating speed during the last decades. The Svínafell outlet glaciers, located on the western side of the Öræfajökull volcano has retreated and thinned considerably from its LIA maximum extend, and from the year 1980 a proglacial lake began to form at the snout of the glacier. Recently a large fracture was detected on the Svínafellsheiði mountains slope above the southern and eastern side of the glacier. This fracture can be traced over 1,7 km from about 850 m a.s.l. down the slope to the surface of the glacier at 300 m a.s.l. It is estimated that about 1 km2 of the mountain slope is unstable, with a minimum of 60 million ton of bedrock can be mobilized. During the summer 2018 the fracture was mapped and GPS stations installed on both sides of the fracture. Two extensometers were installed on the uppermost part of the fracture and DEM made from drone images on the unstable slope.
This project will be primarily conducted at the Institute of Earth Science, University of Iceland, in collaboration with NTNU and NGU in Trondheim, Norway. The project focus on slope stability analysis of the mountain slope and participation in mapping of different geological units and fractures in the bedrock. The work require considerably fieldwork at the Svínafellsheiði Mountain.
NordVulk collaborator: Þorsteinn Sæmundsson, University of Iceland
Nordic collaborators: Reginald Hermanns at NTNU and NGU in Trondheim, Norway
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12. Shallow magma storage in Jan Mayen and it’s sensibility to ice fluctuation (physical volcanology, petrology and geochemistry)
This project seeks to understand the linkage between climatically induced glacial unloading and volcanic eruptions. Preliminary data from the island of Jan Mayen suggests that periods of deglaciation were accompanied by enhanced volcanic activity which we hypothesize were due to pressure reduction above shallow magma chambers. To test this hypothesis, three time-periods with glacial unloading and plentiful evidences of volcanic activity will be targeted; the two warming periods causing deglaciation subsequent to the Last Glacial Maximum and the Little Ice Age, and the ongoing warming causing present glaciers to retreat. The area of Jan Mayen offers unique opportunities to study this climate relationship of the earth system. The fundamental scientific outcome of the proposed research and its applied aspects have implications far beyond the study area.
Ice unloading, both total effect and rate of change, is key to investigate possible effects on shallow magma chambers.
The idea about ice sheets or ice caps being able to trigger increased melting in the mantle is not under question here. Instead, we suggest looking into ready formed magma that is stored at shallow depth, as it is more vulnerable to small pressure changes due to overlying ice sheets. Any magma body that is at equilibrium at a given depth in the crust is particularly sensitive to decrease in pressure, since it affects its ability to hold volatiles in solution. Volatiles in solution will escape if pressure drops and form bubbles. The bubble formation has the effect of lowering magma density and thus increase its eruptability. In this project we shall use petrographic and crystal chemistry to estimate depth of magma storage in Jan Mayen. Further we shall use glass chemistry and crystal inclusions to estimate volatile content of the magma prior to eruption. The aim is to define magma sensitivities to overburden pressure for erupted magmas on Jan Mayen. Further magmas stored at different depths will be used to estimate if global warming leading to continued deglaciation will increase the risk of volcanic eruptions on the Island. Two future climate-glacier scenarios are planned; One by removing half of the present glacier volume, and the second by removing all present ice. When or if this is likely to happen depends on future climate scenarios. In the 1970's the equilibrium line altitude (ELA) for glaciers around Beerenberg varied between some 950 to 600 m a.s.l. depending on glacier aspect. These ELA data, the higher ELA values of today, and climate scenarios will be used to estimate rate of future glacier change.
NordVulk collaborator: Ármann Höskuldsson
Collaborators: NGU, NUST-Trondheim, University of Bergen, Uniiversity of Stockholm, Uniniversity of Bern (Switzerland).
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