here - ETH Zürich

The dynamics of magma in a convecting mantleR. F. KatzDepartment of Earth Sciences, University of Oxford, UKrichard.katz@earth.ox.ac.ukI will derive and review a standard formulation of the "magma dynamics" equationsgoverning conservation of mass and momentum for the magma/mantle system. To buildinsight into the behavior of the system, I will review the results of a series of modelcalculations of increasing complexity. These calculations will focus on wave and localizationphenomena in magma dynamics. I will then show how a thermodynamic formulation adaptedfrom the metallurgical literature (the Enthalpy Method) can facilitate the solution of tectonicscaleproblems in magma-dynamics. Enthalpy Method-based simulations of magma genesisand transport beneath a mid-ocean ridge will be presented as an illustration of the power ofthis approach.Tectonics and geodynamics of the AlpsE. KisslingInstitute of Geophysics, ETH Zurich, Switzerlandkiss@tomo.ig.erdw.ethz.chThis presentation aims to serve as an introduction to geology, tectonics, andgeodynamics of the Alps in combination with the proposition of a few plate tectonichypotheses testable by geodynamic modeling that are based on current knowledge of deepstructure and orogen evolution. By modeling Alpine lithospheric structure with simplifiedgeneric plate-tectonic processes we aim to further our understanding of current and pastorogenic driving forces.The Alps are the product of a classical Wilson cycle that begun with the opening of theAlpine Tethys between Eurasia in the north and Africa -with Adria attached- in the south inmesozoic times. In contrast to the wide ocean further east, by mid cretaceous time the westernTethys consisted of a series of relatively small ocean basins of different ages interconnectedby even narrower channels largely underlain by oceanic and sometimes by extendedcontinental lithosphere. Furthermore, the region between the two large plates over the pastfew 100Ma contained a number of small-sized and micro-continental plates that variablyseparated from and amalgamated with the larger plates similar to the current situation in theMediterranean. Convergence between the two large plates Africa and Europe since latecretaceous lead to subduction of oceanic lithosphere and subsequent collision of continentallithosphere in the tertiary. A number of peculiarities, however, distinguish the Alpine orogenyfrom others and they left their specific marks clearly visible in current deep lithospherestructure and tectonics. Presently, the Alps exhibit an uplift rate of about 2mm/y, a similarerosion rate and in relation to this vertical motion a very slow convergence rate of only 1-2mm/y. This slow convergence corresponds with relatively short and small lithosphere mantleslabs that exert only limited pull to the Adriatic micro plate in the south and negligable pull tothe large Eurasian plate. Furthermore, geometry of the two slabs and lower crustal indentationstructure in the Central and Western Alps suggests the subduction-collision zone is largelylocked. The two almost opposing slabs correspond well with surface geology where in the east17