Plate tectonics is the theory that explains continental drift as the result of Earth's outer surface being broken into plates that move and slide past each other over geological time. The youngest portion of the plates are generated by seafloor spreading at volcanic ridges in the world?s oceans which replaces the older portions of the plates that get recycled back into the Earth's interior through a process known as subduction. When this theory was formulated during the 1960's, it was a scientific revolution for Earth sciences on par with the theory of evolution for biology and quantum mechanics for physics, as it provides a conceptual framework for understanding Earth's tectonism and volcanism in a unifying way. However, this initial theory was merely a descriptive set of rules for the kinematics of plate motion. Our lack of a deeper understanding is highlighted by questions such as: How does plate tectonics work? When did plate tectonics begin? And Why does Earth have plate tectonics? The answers to these questions are central for learning more about the evolution of Earth?s continents, oceans, atmosphere, and even life itself. This project will investigate the dynamical causes for unusually rapid motion of the Indian plate observed between 70 and 45 Million years ago (Ma), when the Indian plate was recorded to have drifted 1.5-2 times faster than the typical speed of subducting plates. By attempting to understand such an anomalously fast plate speed, our knowledge of how plate tectonics works, and how Earth has evolved, will be improved. A significant aspect of this project is its innovative educational component, a pilot-scale nationwide REU program in geodynamics aimed to strengthen the applicant pool of highly qualified prospective PhD students within geodynamics and increase participation from members of underrepresented groups. This program will support four undergraduate researchers each summer with one hosted by PI-Stegman at SIO and three others hosted by participating institutions across the nation. All REU participants will work on an engaging, well-designed project that directly advances the research and educational objectives of the overall project,including authorship of subsequent publications to which their work over the summer contributed. This initiative provides a framework for community building by strengthening ties between computational geodynamics groups nationally, by offering the mutual benefit of an enhanced ability to successfully attract and recruit highly qualified PhD students.
Beginning at 67 Ma, the Indian plate achieved peak velocities in excess of 16 cm/yr, or nearly double the typical velocity of subducting plates (∼6-8 cm/yr), and then sustained speeds in excess 10-12 cm/yr until 52 Ma. The start of this remarkable event is coincident with the arrival of the Deccan plume head that is thought to have produced an enormous volcanic eruption known as the Deccan traps. This project will build upon the recent discovery of a new plate driving force, the plume-push force (Cande and Stegman, 2011), which may play a role in explaining the fast motion of India in addition to slab-pull and ridge-push forces acting on the system. Current observations suggest mantle plumes influence both plate motions as well as where plate boundaries form, but the underlying physical process for how and why is not yet known. Numerical models of mantle convection will be employed to systematically investigate the motion of India, and will be constrained by a diverse suite of geophysical and geological observations. Furthermore, the physical mechanism through which the plume-push force acts will be quantitatively investigated with geodynamic models. Lastly, this project will investigate the physical mechanism that allows a plumehead to facilitate plate boundary reorganizations over short intervals of time (5-10 Myr), as indicated by the tectonic history of the Seychelles microplate between 70-60 Ma which can be used to add spatial-temporal constraints on the uplift and horizontal force-balance evolution. The outcomes of this project will advance the capability to model plate tectonics in a way yet to be achieved: as a fully-dynamic, time-dependent 3D system with self-consistently evolving plate driving forces.
