The Long Term Tectonics Working Group aims to provide numerical tools to researchers who investigate the behavior of the lithosphere and upper mantle over time scales on the order of 10^4-9 years. Studies undertaken by the LTT community commonly focus on subduction of the tectonic plates, creation and evolution of mid-ocean ridges, upwelling and self-spreading of sub-lithospheric mantle plumes, and large-scale continental deformation. Such simulations are complex and involve multiple scales of interaction between materials of widely varying rheologies, from linear/non-linear viscous to brittle faulting, as well as other multi-physics problems like two-phase flow of melts or other fluids and chemical evolution during the above processes.