HR: 08:30h
AN: V31F-03    [Abstracts]
TI: Deformation of Torfajokull Caldera, Iceland
AU: Scheiber, S C
EM: Stephanie.Scheiber@students.wits.ac.za
AF: University of the Witwatersrand, School of Geosciences Private Bag 3, Johannesburg, PA 2050, South Africa
AU: * LaFemina, P
EM: plafemina@geosc.psu.edu
AF: Penn State, Dept. of Geosciences 406 Deike Bldg, University Park, PA 16802, United States
AU: Sturkell, E
EM: sturkell@hi.is
AF: Nordic Volcanological Center, University of Iceland Askja, Reykjavik, FL 101, Iceland
AB: The Mid-Atlantic Ridge, the plate boundary between the North American and Eurasian tectonic plates, is expressed in Iceland as neovolcanic zones consisting of central volcanoes and fissure swarms. The Mid-Atlantic Ridge becomes subaerial here due to its position above the North Atlantic mantle plume. In south Iceland plate motion is accommodated across the western and eastern volcanic zones. The eastern volcanic zone (EVZ) is thought to have formed approximately 2-3 Ma and is propagating to the southwest into crust formed during the Tertiary in the western volcanic zone. This has resulted in the formation of more evolved volcanic systems of the eastern volcanic flank zone (EVFZ). Torfajokull caldera is located at the intersection of the EVZ and EVFZ, has been active since late Quaternary time, with the most recent eruption in 1477 AD, and is the largest rhyolitic complex in Iceland. The caldera hosts the largest geothermal field in Iceland and therefore has been the focus of ongoing geophysical and geologic investigation. This study investigates the complex interplay between plate spreading and volcano deformation at this caldera using space geodetic and modeling techniques. We present horizontal and vertical velocity fields based on episodic GPS measurements collected between 2000- 2006. In a stable Eurasian reference frame the horizontal signal is dominated by plate spreading through the caldera, in agreement with known Holocene fissuring northeast and southwest of the caldera and the results of LaFemina et al. (2005). The horizontal velcoity field also indicates the interaction of Hekla volcano, 20 km west- northwest, which has been uplifting since erupting in 2000. Vertical rates on average exceed 15 mm/yr and may indicate glacio-isostatic adjustment. Nevertheless, colocated GPS and dry tilt in the center of the caldera indicate subsidence at up to 10 mm/yr.
DE: 1032 Mid-oceanic ridge processes (3614, 8416)
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 6929 Ionospheric physics (1240, 2400)
DE: 8440 Calderas
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting