This paper provides a hypothesis to account for the two Large Low-Shear-Velocity Provinces (LLSVPs) and discusses evidence supporting this hypothesis. These features are located in the lower mantle just above the core-mantle boundary and display strikingly low seismic-shear wave speed relative to adjacent rock. They are nearly antipodal to each other, with one lying roughly beneath Africa and the other beneath the central Pacific Ocean. While secular literature does not have an explanation for how these structures arose or even why they display such low seismic speeds, we postulate that LLSVPs are a direct consequence of catastrophic plate tectonic activity during the Genesis Flood. This paper posits that LLSVPs correspond to hot lower-mantle rock that was forcibly shoved aside by subducted lithospheric slab material as it reached the core-mantle boundary during the Flood. The large contrast in seismic speed between the LLSVP material and the surrounding rock is due primarily to the large difference in temperature. The apparent paradox of why these two LLSVPs, if their low seismic speed is due to high temperature and reduced density, did not rise to the surface millions of years ago is resolved by the realities that the Flood occurred only a few thousand years ago and that mean mantle viscosity returned quickly to its present value at the end of the cataclysm. Numerical simulations with the mantle dynamics code, terra, support this scenario.