Paper No. 3
Presentation Time: 8:45 AM
INTERPRETING THE EVOLUTION OF EARTH'S SURFACE TOPOGRAPHY IN TERMS OF MANTLE CONVECTION
FORTE, Alessandro M.1, MOUCHA, Robert
2, ROWLEY, David B.
3, GLISOVIC, Petar
1, MITROVICA, Jerry X.
4, SIMMONS, Nathan A.
5 and GRAND, Stephen P.
6, (1)Geotop, Département des Sciences de la Terre et de l'Atmosphère, Université du Québec à Montréal, CP 8888, succursale Centre-Ville, Montreal, QC H3C 3P8, Canada, (2)Department of Earth Sciences, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244, (3)Department of the Geophysical Sciences, The University of Chicago, 5734 S. Ellis Avenue, Chicago, IL 60637, (4)Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, (5)Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, CA 94550-9234, (6)Department of Geological Sciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, forte.alessandro@uqam.ca
The present-day topography of the Earth may be interpreted as the superposition of two long-term contributions: the first originating from the isostatic compensation of lateral changes in crustal thickness with minor contributions from density and the second from the dynamic vertical stresses on the surface generated by the convecting mantle. Short-term transient topography changes due to isostatic disequilibrium, particularly from glacial adjustment (i.e. GIA), represent a third contribution. While changes in crustal structure (mainly through tectonism, erosion and deposition) will produce time-dependent changes in the first contribution, we will focus here on the temporal evolution of the second contribution: namely the changing vertical stresses generated by the highly time-dependent convective circulation in the mantle.
Our ability to understand the impact of convection dynamics deep inside the mantle on time-dependent surface topography has made substantial progress over the past few years (e.g. Moucha et al., EPSL 2008; Spasojevic et al., GRL 2008). Recent progress has been achieved thanks to advances in tomographic imaging of the 3-D structure in the Earth's interior by simultaneously inverting global seismic, geodynamic and mineral physical data sets (Simmons et al., GJI 2009, JGR 2010). The most recent tomography-based simulations of mantle convection reveal the surprisingly large and crucial role of large-scale hot, active upwellings in controlling not only the heat flow across the mantle but also the topographic evolution of our planet. These tomography-based convection models are providing new views on how deep-mantle dynamics affects the surface evolution of our planet (Glisovic et al., GJI 2012). As we demonstrate, the convective contributions to surface topography are large and rapidly changing: generating as much as 2 km of topography in the East African Rift over the past 30 million years (Moucha & Forte, Nat. Geosci. 2011). These rapid changes due to the buoyancy of hot mantle are also shown to be fundamental to the interpretation of the topographic evolution of the U.S. East Coast since the mid-Pliocene (Rowley et al., Sci. 2013).
