The Formation and Stabilization of Thickened Lithosphere

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Continents, covering only ~30% of the Earth's surface, are the sole location of human habitation, yet, unfortunately are also regions of widely distributed deformation resulting in earthquakes, volcanism, landslides, etc. Ultimately, these destructive processes are the consequence of the Earth losing heat that is stored & generated (via decay of radioactive material) within its interior. How this energy translates into the processes that shape the continent's surface still remains an outstanding challenge with great significance for understanding what makes some regions tectonically "safe" versus potentially dangerous. Fortunately, the Earth provides unique insight into its tectonic evolution via areas of the continental interior called cratons. Cratons are thick (~200-300km), old (~3-4 billions of years) regions that have avoided deformation since their origin. Meaning that for the majority of Earth's history while the rest of the Earth's surface was being modified by tectonic processes, cratons resisted being split apart, broken up, compressed or remelted. This longevity and survivability of cratons provides understanding of the driving forces behind deformation over Earth's history. This study aims to increase our understanding of this problem by focusing on mapping out when, how and why thick, stable continental lithosphere forms as well as assessing the future survivability and longevity for current tectonically stable regions of the Earth.This project combines theoretical scalings with two- and three-dimensional time-dependent numerical models to quantitatively determine the dynamic conditions required to thicken and stabilize lithosphere. It will consider two different candidates to make thickened cratonic lithosphere from - buoyant oceanic lithosphere and island arc material. It will also explore the role of a secondary process whereupon the removal of a dense layer (such as eclogite or mafic cumulates) helps promote the stability of cratonic lithosphere. It will compare the generated rheological and composition structure within simulations against seismic observations of the interior of deep cratonic lithosphere. Finally, It will address the size, frequency and nature of drips potentially arising from the base of cratonic lithosphere. By focusing on a critical stage in continental evolution, this work will provide new constraints into the dynamics of the early Earth during which the cores of continental lithosphere were formed.