Top-Down Tectonics?

Geophysicists disagree whether Earth's mantle is a single convective cell or whether it is divided into convective layers. In his Perspective, Anderson reviews the evidence and concludes that the case for layered convection is strong. He also argues that plate tectonics may be driving upper mantle convection, rather than the other way around as traditionally believed. Sophisticated convection simulations will be needed to test this hypothesis.