Gravity and elevation changes caused by magma movement beneath the Krafla Caldera, Northeast Iceland
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Prior to the present activity of the Krafla volcano, which started in 1975, levelling and gravity surveys had been carried out in the area. The network has since been extended, and measurements are carried out about every second month. The measurements reveal a quasi-periodic behaviour of the tectonic activity, characterized by slow inflation of the caldera for several weeks or months at a rate of 6–10 mm/d, interrupted by sudden subsidence events lasting for one or a few days. Elevation changes within the caldera are described by a deflation-inflation swelling with its apex near the center of the caldera. Calculations. using a model of a spherical chamber with varying pressure at 3 km depth, show good agreement with the measured elevation values. Comparison of gravity and levelling data, using a Bouguer type relationship, suggests that inflation and deflation of the floor of the caldera is caused entirely by in- and outflow of magma. Some discrepancies between the levelling and gravity data immediately after subsidence events can be explained by additional mass flow of groundwater.
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Bjornsson, A., Johnsen, G.V., Sigurdsson, S., Thorbergsson, G., Tryggvason, E. (1979) Rifting of the plate boundary in North Iceland 1975-1978. J. Geophys. Res. 84 (In press)
Bjornsson, A., Saemundsson, K., Einarsson, P., Tryggvason, E., Gronvald, K. (1977) Current rifting episode in North Iceland. Nature 266:318-323
Brandsdottir, B., Einarsson, P. (1979) Seismic activity associated with the September 1977 deflation of the Krafla central volcano in NE-Iceland. J. Volc. Geotherm. Res. (In press)
Einarsson, P. (1978) S-wave shadows in the Krafla caldera in NE-Iceland, evidence for a magma chamber in the crust. Bull. Volcanol. 41:1-9
Gerke, K. (1974) Crustal movements in the Myvatn- and the Thingvallavatn-area, both horizontal and vertical. In: Kristjansson, L. (Ed.) Geodynamics of Iceland and the North Atlantic area, pp. 263-275. D. Reidel Publishing Company, Dordrecht, Boston
Gerke, K. (1977) Uber neuere horizontale und vertikale Krustenbewegung in Island. Mitteilungen der Technischen Universitat Carolo-Wilhelmina zu Braunschweig XII, Heft III/IV
Gerke, K., Moller, D., Ritter, B. (1978) Geodatische Lagemessungen zur Bestimmung horizontaler Krustenbewegungen in NordostIsland. In: Festschrift fur W. Hopcke, Wiss. Arb. d. Lehrst. f. Geodasie, Photogramm. u. Kartogr. an d. T.U. Hannover, Nr. 83, Hannover
Hunt, T.M. (1976) Recharge of water in Wairakei geothermal Field determined from repeated gravity measurements. N. Z. J. Geol. Geophys. 20:307-317
Ito, K., Kennedy, G.C. (1971) An experimental study of the basaltgarnet granulite-eclogite transition. In: Heacock, J.G. (Ed.) The structure and physical properties of the Earth's crust, Vol. 14:303-314. Washington, D.C. Geophys Monogr. Am. Geophys. Union
Longman, J.M. (1959) Formulas for Computing the tidal accelerations dueto the Moon and the Sun. J. Geophys. Res. 64:2351-2355
Moller, D., Ritter, B. (1980) Geodetic measurements and horizontal crustal movements in the rift zone of NE-Iceland. J. Geophys. 47:110-119
Mogi, K. (1958) Relations between the eruptions of various volcanoes and the deformation of the ground surfaces around them. Bull. Earthq. Res. Inst. 36:99-134
Niemczyk, O. (1943) Spalten auf Island. Wittwer, Stuttgart
Palma son, G. (1971) Crustal structure of Iceland from explosion seismology. Soc. Sci. Islandica, Rit XL
Palmason, G., Nilsen, T.H., Thorbergsson, G. (1973) Gravity base station network in Iceland 1968-1970. JOkull 23:70-125
Saemundsson, K. (1974) Evolution of the axial rifting zone in Northern Iceland and the Tjornes Fracture Zone. Geol. Soc. Am. Bull. 85:495-504
Saemundsson, K. (1978) Fissure swarms and central volcanoes of the neovolcanic zones of Iceland. In. Crustal evolution in Northwest Britain and adjacent regions. Geol. J. Spec. Issue 10:415-432
Schleusener, A., Torge, W. (1971) Investigations of secular gravity variations in Iceland. J. Geophys. 37:679-701
Schleusener, A., Torge, W., Drewes, H. (1976) The gravity field of Northeastern Iceland. J. Geophys. 42:27-45
Sigurdsson, O. (1976) Natturuhamfarir i Thingeyjarthingi (In Icelandic with English summary). Tyli 6:3-20
Spickernagel, H. (1966) Hohenmessungen in Nord-Island. Mitt. Markscheidewesen 73:139-152
Torge, W., Drewes, H. (1977a) Gravity variations with time in Northern Iceland 1965-1975. J. Geophys. 43:771-790
Torge, W., Drewes, H. (1977b) Gravity changes in connection with the volcanic and earthquake activity in Northern Iceland 1975/1976. Jokull 27:60-69
Torge, W., Kanngieser, E. (1980) Gravity and height variations during the present rifting episode in northern Iceland. J. Geophys. 47:125-131