New Zealand Journal of Geology and Geophysics abstracts

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Emplacement of the large andesite lava flow in the Oturere Stream valley, Tongariro Volcano, from airborne interferometric radar

N. F. Stevens

Active Landscapes Section
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
email: n.stevens@gns.cri.nz

Abstract   The prehistoric eruption of an exceptionally large andesitic lava flow into a glacial valley on the eastern flanks of Tongariro Volcano, North Island, New Zealand, prompts questions about its size and emplacement behaviour. In November 1996, the area was mapped topographically to a high resolution by the NASA TOPSAR airborne interferometric radar instrument. The resulting digital elevation model (DEM), with a spatial resolution of 10 m and a vertical accuracy of 1-3 m, allowed the lava volume to be constrained by two methods: from an estimation of the mean lava thickness from the flow margins, and from low-order polynomial interpolation of the underlying valley form. The TOPSAR DEM provided uniquely detailed measurements of the surface features of the flow-most notably, the levees and surface folding-which show that the lava was emplaced in one broad channel. Analysis of the surface features, in context with the surrounding topography, shows that the surface folding in the medial area of the flow was caused largely by the topographic constraint. This is a previously unobserved cause of surface folding in andesite lava flows.

Keywords   Tongariro Volcano; Oturere Stream valley; andesite lava flow; lava volume; lava surface features; NASA TOPSAR airborne interferometric radar; digital elevation model

G01010 Received 27 April 2001; accepted 30 May 2002; published 27 September 2002
New Zealand Journal of Geology & Geophysics, 2002, Vol. 45: 387-394
0028-8306/02/4503-0387 $7.00/0 © The Royal Society of New Zealand 2002

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