Geodynamics of continents and convergent plate margins

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Geological features, such as mountains, volcanoes and economic mineral deposits, are the result of processes occurring below the Earth's surface and depend directly on the composition, temperature, and stress. Some processes occur within minutes (e.g., earthquakes) while others take millions of years (e.g., mountain-building). My research program addresses processes that occur over long timescales, focusing on western North and South America. Both areas are characterized by large mountain belts that formed as oceanic tectonic plates descended below the continent, a process called subduction. However, the details of continental deformation and mountain-building remain poorly understood. In some places, enhanced deformation may have resulted as the oceanic plate travelled subhorizontally below the continent (termed flat-slab subduction). In addition to regional deformation, the mountain belt is affected by local gravitationally-driven deformation within the crust and rigid mantle. For North and South America, deformation occurs within 500-1000 km of the coast. The eastern limit corresponds to areas of older continent, believed to be too cold and strong to deform. My program aims to understand the dynamics of subduction and mountain-building. Over the next five years, my group will study three main topics: a) an assessment of flat-slab subduction and its effect on continent deformation b) an analysis of local-scale dynamics within mountain belts, including gravitational thinning and lateral flow of weak crust c) an examination of the east boundary of the mountain belt. Why does the adjacent continent not deform, and does the geometry of the boundary provide clues to mountain belt formation? This work will be carried out with 8 graduate students and at least 5 undergraduates. We will use computer models to study the dynamics of deformation over millions of years. The models provide quantitative predictions for the surface geological record (e.g., changes in topography) and geophysical measurements (e.g., spatial variations in seismic velocity). Comparisons with existing observations in western North and South America allow us to determine whether the model behaviours are reasonable. Conversely, the models enhance the interpretation of observations and point to areas where new data is needed. This research provides insight into mountain-building and how subsurface processes are recorded in surface geology. Our work will focus on western North and South America, but we aim to identify fundamental processes relevant to subduction zones globally. Our models also provide information about the temperature and stress conditions in the Earth. Thus, this work is relevant to understanding the conditions for short-term deformation (i.e., earthquakes and seismic hazard assessment), as well as geothermal energy evaluation, hydrocarbon potential and mineral/diamond exploration.