The Birth and Evolution of Plate Boundary Systems: The Critical Role of Strain Rate

Nicolas Roberts, Department of Geosciences, Hamilton College
Folarin Kolawole, Department of Earth and Environmental Sciences, Columbia University
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Abstract

The development, localization, and maturation of plate boundary fault systems involves complex interactions between a wide variety of geologic processes: relative plate motion drives frictional and viscous behavior of the lithosphere; lithospheric and crustal thinning, or magmatism can change geothermal gradients; rock-fluid interactions can change the frictional strength of the lithosphere; and structural inheritance can influence where localization might occur. In the viscous portions of the lithosphere, differential stress (i.e., rock strength) is proportional to strain rate and depends on the rheology(ies) of the deforming material(s). To understand how stress is distributed throughout the lithosphere, it is imperative to consider how strain rate (and strength) evolves as incipient plate boundaries localize and mature. In this talk, we consider three central questions with data and examples from the evolving East African Rift System: 1) What processes drive localization and strain-rate increase in relatively homogeneous mantle lithosphere? 2) How does this strain rate increase affect the lithospheric strength profile through time? and 3) How might continental crust of different compositions evolve in distinct ways? Central to each of these questions is the strain rate feedback between the nominally brittle and viscous portions of the lithosphere.

Session

Large-scale tectonics