Alessandro Forte

Fellow: Awarded 2013

Field of Study: Earth Science

Competition: US & Canada

Website: http://www.geotop.ca/en/le-geotop/membres/reguliers/74-forte-alessandro.html

Alessandro M. Forte was born in Rome, Italy, but pursued his university studies in Canada, where he graduated with a Ph.D. in geophysics from the Department of Physics at the University of Toronto in 1989. Although he initially completed an engineering degree in Toronto, and was subsequently engaged in graduate studies in theoretical physics, it was the application of physics to the Earth that provided the ultimate and enduring lure. His doctoral thesis focused on numerical models of how hot, solid rocks, deep below the crust, creep slowly over geological time and how this movement of mass and heat—a process called "thermal convection"—is manifested at the surface in the horizontal motions of Earth's tectonic plates and the associated "drift" of the continents. Understanding how our entire planet functions, as a dynamic system that spans all depths from the innermost core to the external crust, has provided an immensely fertile and passionate avenue of research that has animated his research and teaching activities for more than two decades.

In a perhaps fitting testament to the Greek root for 'planet' (planetes: wanderer), Alessandro Forte has travelled the globe to follow his vocation. After his doctorate, he moved to Boston to begin a new phase of work on global imaging of the 3-D structure deep inside the Earth, using a technique called "seismic tomography" that is analogous to CAT-scanning the innards of the Earth. This research, carried out at Harvard University in collaboration with renowned seismologist Adam Dziewonski, opened the door to a comprehensive new understanding of both the structure and dynamics inside our planet. After nearly five years in Boston, he relocated to France to take up a faculty position at the Institut de Physique du Globe de Paris, where he was privileged to interact with world-class scientists for five years. After returning to Canada, he worked at the University of Western Ontario (UWO) for another five years until finally moving to Montreal, in 2003, to take up his current position as Canada Research Chair at the University of Quebec at Montreal (UQAM). An inveterate scientific traveller, he has also been a visiting professor at universities in Japan (Tokyo), Netherlands (Utrecht), France (Paris, Grenoble), and Switzerland (Zurich).

Over this two-decade period of travel and research, Alessandro Forte has dedicated himself to developing a detailed physical model of how movements of mass and heat (i.e., thermal convection) deep inside the rocky mantle, extending from the bottom of the crust down to the Earth's core, exert a profound control on the surface geological evolution of the Earth. Some highlights of this work include a demonstration of how changes in Earth's shape driven by convection in the mantle could alter the tilt and spin of the Earth's rotation axis as it orbits the sun and thus perturb the climate of our planet ("A Resonance in the Earth's Obliquity and Precession over the Past 20 Myr Driven by Mantle Convection", published in 1997 in Nature). Subsequent work revealed that the immense, plume-shaped regions of hot rock below Africa and the Pacific Ocean are actively rising upwards to the surface and provide at least half the driving force for the convective movements inside the mantle, as well as providing a major push to the tectonic plate motions and variations in Earth's gravity field ("Deep-Mantle High-Viscosity Flow and Thermochemical Structure Inferred from Seismic and Geodynamic Data", published in 2001 in Nature). A crucial control on geological evolution at the Earth's surface comes from the changes to the topography of continents and the depths of ocean basins that are driven by mantle convection. This link between topography and internal dynamics was clarified in a number of studies (including, for example, "Geodynamic Evidence for a Chemically Depleted Continental Tectosphere", published in 2000 in Science, and "Changes in African Topography Driven by Mantle Convection", published in Nature Geoscience in 2011) that all stemmed from initial work published in 1993 in Geophysical Research Letters (entitled "Dynamic Surface Topography: A New Interpretation Based Upon Mantle Flow Models Derived From Seismic Tomography").

Alessandro Forte has recently focused on developing a significantly revised model of mantle convection that will imply a major shift of a long-standing paradigm, or standard model, of how plate tectonics is related to, and driven by, the flow deep inside the Earth. His newest work reveals the surprisingly large role of super-plumes in the convecting mantle, in particular below Earth's fastest spreading midocean ridge (the East Pacific Rise). This discovery, coupled with new findings of large amounts of heat that enter the mantle from the core, suggests the current standard model of mantle convection mainly driven by the descent, or "subduction," of tectonic plates into the mantle is no longer tenable. This exciting new work will be at the center of Alessandro Forte's research activities during his tenure as Guggenheim Fellow.

Among the honors received by Alessandro Forte are appointments as Senior Fellow in the Canadian Institute for Advanced Research and as a Canada Research Chair at UQAM.


Profile photograph: Alessandro Forte in native Roman habitat.