Thick lava flows of Karisimbi Volcano, Rwanda: insights from SIR-C interferometric topography |
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| Authors: | Mary E MacKay Scott K Rowland Peter J Mouginis-Mark Harold Garbeil |
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| Institution: | (1) Hawaii Institute of Geophysics and Planetology, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822, USA Fax: +808 956 6322 e-mail: mackay@soest.hawaii.edu, US |
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| Abstract: | We use a digital elevation model (DEM) derived from interferometrically processed SIR-C radar data to estimate the thickness
of massive trachyte lava flows on the east flank of Karisimbi Volcano, Rwanda. The flows are as long as 12 km and average
40–60 m (up to >140 m) in thickness. By calculating and subtracting a reference surface from the DEM, we derived a map of
flow thickness, which we used to calculate the volume (up to 1 km3 for an individual flow, and 1.8 km3 for all the identified flows) and yield strength of several flows (23–124 kPa). Using the DEM we estimated apparent viscosity
based on the spacing of large folds (1.2×1012 to 5.5×1012 Pa s for surface viscosity, and 7.5×1010 to 5.2×1011 Pa s for interior viscosity, for a strain interval of 24 h). We use shaded-relief images of the DEM to map basic flow structures
such as channels, shear zones, and surface folds, as well as flow boundaries. The flow thickness map also proves invaluable
in mapping flows where flow boundaries are indistinct and poorly expressed in the radar backscatter and shaded-relief images.
Received: 6 September 1997 / Accepted: 15 May 1998 |
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| Keywords: | Karisimbi Virunga Viscous lava flows Lava rheology Remote sensing |
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