Mantle avalanches and the dynamic topography of continents

The dynamic topography of continents associated with mantle avalanche events are discussed. Our flow simulations involve two-dimensional axisymmetric multi-phase mantle models which incorporate compressibility and a realistic, factor of ∼ 40, increase in viscosity with depth. The surface kinematic boundary conditions involve a mix of free and rigid (i.e., no-slip) constraints, with the latter intended to mimic the influence of a spherical continental cap. We find that avalanche events support regional vertical deflections of up to ∼ 2.5 km. The horizontal length scale of the dynamic topography is ∼ 2500 km and non-negligible deflections can persist on the order of 100–200 Ma. We also find that convergence rates in regions surrounding the continents are variable but can reach rates of the order of 3 cm/a. Finally, we speculate that an avalanche event may have been responsible for the development of the large-scale intracontinental basin system in the western interior of North America from the Early Devonian to Late Carboniferous [1].