Fast plumeheads: Temperature‐dependent versus non‐Newtonian rheology

In a series of two‐dimensional Cartesian simulations with high resolution, on the order of 2 km, we have compared for the same effective Rayleigh number, around 106, the dynamics between Newtonian and non‐Newtonian rheologies. A viscosity contrast due to temperature of 1200 has been employed throughout with surface dissipation numbers varying between 0.05 and 0.2. Peak velocities for non‐Newtonian plumes are at least 50 times faster than the peak Newtonian velocities and reach magnitudes in excess of m/yr. Upon impinging the surface, plume head structures of the non‐Newtonian rheology contain much greater complexity in the thermal‐mechanical structure than for Newtonian plumes.