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- Gee, David G., et al.
(författare)
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Nordic Geoscience and the 33rd International Geological Congress: Introduction
- 2008
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Ingår i: Episodes. - : International Union of Geological Sciences. - 0705-3797 .- 2586-1298. ; 31:1, s. 4-8
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Tidskriftsartikel (refereegranskat)abstract
- Geology has been of profound importance for the Nordic countries since the Middle Ages. Strong economies were built on an understanding of the occurrence in bedrock of minerals containing metals, e.g., silver, copper, zinc and iron, and eventually led to the establishment of the first Geological Surveys in Norway and Sweden in the middle of the nineteenth century. The geology of Norden ranges from the oldest to youngest rocks on the planet. Based on the papers in this special issue, this introduction provides a brief summary of the geological evolution of Norden, from the Archean of Greenland and northern Fennoscandia to the on-going volcanicity in Iceland on the Mid-Atlantic Ridge. It also refers to aspects of Geoscience that are particularly important for society in Norden, including geo-resources (petroleum, geothermal energy, nuclear energy, metals, industrial minerals and groundwater) and environmental geology (including natural and anthropogenic processes, medical geology, geo-hazards and climate). Information on the early history of geology in Norden and the geological surveys is also included and, finally, an outline of the 33rd International Geological Congress with its main theme “Earth System Science: Foundation for Sustainable Development”.
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- Pagli, Carolina, et al.
(författare)
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Glacio-isostatic deformation around the Vatnajökull ice cap, Iceland, induced by recent climate warming : GPS observations and finite element modeling
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:B8, s. B08405-
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Tidskriftsartikel (refereegranskat)abstract
- [1] Glaciers in Iceland began retreating around 1890, and since then the Vatnajokull ice cap has lost over 400 km 3 of ice. The associated unloading of the crust induces a glacio-isostatic response. From 1996 to 2004 a GPS network was measured around the southern edge of Vatnajokull. These measurements, together with more extended time series at several other GPS sites, indicate vertical velocities around the ice cap ranging from 9 to 25 mm/yr, and horizontal velocities in the range 3 to 4 mm/yr. The vertical velocities have been modeled using the finite element method (FEM) in order to constrain the viscosity structure beneath Vatnajokull. We use an axisymmetric Earth model with an elastic plate over a uniform viscoelastic half-space. The observations are consistent with predictions based on an Earth model made up of an elastic plate with a thickness of 10-20 km and an underlying viscosity in the range 4-10 x 10(18) Pa s. Knowledge of the Earth structure allows us to predict uplift around Vatnajokull in the next decades. According to our estimates of the rheological parameters, and assuming that ice thinning will continue at a similar rate during this century (about 4 km 3/year), a minimum uplift of 2.5 meters between 2000 to 2100 is expected near the current ice cap edge. If the thinning rates were to double in response to global warming (about 8 km 3/year), then the minimum uplift between 2000 to 2100 near the current ice cap edge is expected to be 3.7 meters.
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- Pinel, Virginie, et al.
(författare)
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Consequences of local surface load variations for volcanoes monitoring: Application to Katla subglacial volcano, Iceland
- 2009
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Ingår i: The VOLUME Project. VOLcanoes: Understanding subsurface mass moveMEnt. Edited by C.J. Bean, A.K. Braiden, I. Lokmer, F. Martini, G.S. O´Brien. - Dublin, Ireland. - 9781905254392 ; , s. 25-39
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Surface load variations occur frequently in the vicinity of volcanoes inducing deformation and stress field perturbations that can be recorded by geophysical monitoring. It is thus necessary to discriminate these perturbations from those caused by shallow magma movement and to understand their potential influence on themagmatic plumbing system. Discrimination can be performed by modelling the deformation induced by surface load variations using integration of Green's function. This method was applied to the Katla volcano located beneath the Mýrdalsjökull ice cap, Iceland, where an annual cycle in ice load occurs as well as a gradual ice retreat. We also estimated pressure changes induced by the seasonal ice load variation within a magma reservoir, and calculated the deformation field and the Coulomb stress changes induced by the combined effect of the ice load variation and the magma pressure re-equilibration. Seismicity rate response to the seasonal perturbation strongly depends on the shape and state of the magma reservoir. Finally, introducing a rupture criterion, we conclude that, in the case of spherical or horizontally elongated reservoir and a slow magma inflow, eruptions at Katla volcano are more likely during the summer period, which is consistent with historical observations.
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