HR: 0800h
AN: V21A-0397    [Abstracts]
TI: Volcano Flank Structures on Earth and Mars
AU: van Wyk de Vries, B
EM: b.vanwyk@opgc.univ-bpclermont.fr
AF: LMV, Université Blaise Pascal, Clermont Ferrand, 63038, France
AU: * Byrne, P K
EM: byrnepk@tcd.ie
AF: Department of Geology, Trinity College Dublin, Dublin, 2, Ireland
AU: Mathieu, L
AF: LMV, Université Blaise Pascal, Clermont Ferrand, 63038, France
AU: Mathieu, L
AF: Department of Geology, Trinity College Dublin, Dublin, 2, Ireland
AU: Murray, J B
AF: Department of Earth Sciences, The Open University, Milton Keynes, MK7 6BJ, United Kingdom
AU: Troll, V R
AF: Department of Geology, Trinity College Dublin, Dublin, 2, Ireland
AB: Shield volcanoes on Earth and Mars share common features, including calderas and pit crater chains. A set of structures present on the sides of several of the large shields on Mars are not regarded as having Earth analogues, however. Flank terraces are topographically subtle structures, characterised by a gentle convex profile and a distinctive "fish scale" imbricate distribution pattern. Magma chamber inflation, lithospheric flexure, flank relaxation, or gravitational slumping have been suggested as terrace formation mechanisms. Terraces on both Mars and Earth are clearly visible only in slope maps, and may thus escape visual detection in the field. We show that both Mauna Loa (Hawaii) and Etna (Sicily) display the same characteristic "fish scale" terrace pattern. This pattern delineates structures that we contend are terrestrial flank terraces. Heterogeneities in volcano geometry, due to buttressing or extension, result in terrace distributions that are not as evenly circumferential as those on Mars. Plan and cross-sectional profiles, however, parallel those of the Martian structures. These structures may also be present on Alayta (Ethiopia), Santa Cruz (Galapagos), and Tendürek Dagi (Turkey). Another type of structure, larger and steeper than flank terraces but sharing a similar plan-view morphology, is also present on Mauna Lau and Etna. These "flank bulges" appear to correlate with structures on Piton de la Fournaise (La Réunion), Cosiguina (Nicaragua), and Karthala (Comoros) on Earth, and Apollinaris Patera and Tharsis Tholus on Mars. Elsewhere (Paul K. Byrne et al., this volume) we argue that lithospheric flexure is a likely formation mechanism for Martian terraces. Flexure is active beneath Mauna Loa, and possibly under Etna, and so may also be responsible for terrestrial flank terraces. Scaled analogue models suggest that the larger flank bulges are due to magma intrusions derived from large chambers within these edifices. There is thus a strong morphological link between deformation, intrusion, and surface topography. Additionally, as these structures occur on both planets, the governing tectonic and volcanological processes are fundamentally the same for Earth and Mars.
DE: 5475 Tectonics (8149)
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 8148 Planetary volcanism (5480, 8450)
DE: 8450 Planetary volcanism (5480, 6063, 8148)
DE: 8485 Remote sensing of volcanoes
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting