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Integration of micro-gravity and geodetic data to constrain shallow system mass changes at Krafla Volcano, N Iceland

de Zeeuw-van Dalfsen, Elske; Rymer, Hazel; Williams-Jones, Glyn; Sturkell, Erik and Sigmundsson, Freysteinn (2006). Integration of micro-gravity and geodetic data to constrain shallow system mass changes at Krafla Volcano, N Iceland. Bulletin of Volcanology, 68(5) pp. 420–431.

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DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1007/s0445-005-0018-5
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Abstract

New and previously published micro-gravity data are combined with InSAR data, precise levelling and GPS measurements to produce a model for the processes operating at Krafla volcano, 20 years after its most recent eruption. The data have been divided into two periods: from 1990 to 1995 and from 1996 to 2003 and show that the rate of deflation at Krafla is decaying exponentially. The net micro-gravity change at the centre of the caldera is shown, using the measured Free Air Gradient, to be -85 μGal for the first and -100 μGal for the second period. After consideration of the effects of water extraction by the geothermal power station within the caldera, the net gravity decreases are -73 ± 17 μGal for the first and -65 ± 17 μGal for the second period. These decreases are interpreted in terms of magma drainage. Following a Mogi point source model we calculate the mass decrease to be ~2 x 1010 kg/yr reflecting a drainage rate of ~0.23 m3/s, similar to the ~0.13 m3/s drainage rate previously found at Askja volcano, N-Iceland. Based on the evidence for deeper magma reservoirs and the similarity between the two volcanic systems, we suggest a pressure-link between Askja and Krafla at deeper levels (at the lower crust or the crust-mantle boundary). After the Krafla fires, co-rifting pressure decrease of a deep source at Krafla stimulated the subsequent inflow of magma, eventually affecting conditions along the plate boundary in N-Iceland, as far away as Askja. We anticipate that the pressure of the deeper reservoir at Krafla will reach a critical value and eventually magma will rise from there to the shallow magma chamber, possibly initiating a new rifting episode. We have demonstrated that by examining micro-gravity and geodetic data, our knowledge of active volcanic systems can be significantly improved.

Item Type: Journal Article
ISSN: 0258-8900
Extra Information: The original publication is available at www.springerlink.com
Keywords: micro-gravity; deformation; Krafla; Askja; magma drainage; InSAR; reservoir
Academic Unit/Department: Science
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 154
Depositing User: Users 12 not found.
Date Deposited: 10 May 2006
Last Modified: 09 Oct 2011 12:50
URI: http://oro.open.ac.uk/id/eprint/154
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