Hotspot Reference Frames: The “Necessity” of Mesoplates

Part of the resistance to Plate Tectonics among earth scientists in the 1960s and 1970s involved the concept of rigidity. When advocates of the new global tectonics spoke of rigid plates, they encountered an intuitive misunderstanding of mechanical rigidity rather than kinematic rigidity. The idea of mesoplates as described below is likely to encounter a similar resistance. Is the domain of the mesoplate likely to be rigid? Isn’t it more likely to behave plastically? Again, from a mechanical perspective, mesoplates, as defined below, may well consist of plastically deformable material at the pressures and temperatures at which it exists, if it is subjected to sufficient stresses. The key condition that allows for both lithoplates and mesoplates is the absence of pervasive stresses within their interiors. Deformation is restricted to the margins of plates — both lithoplates (of classic Plate Tectonics) and mesoplates.