PLATE MOTIONS, BOUNDARY FORCES, AND HORIZONTAL TEMPERATURE-GRADIENTS - IMPLICATIONS FOR THE DRIVING MECHANISM

Largely because of the wide variety of observational constraints which must be satisfied, the search for a viable driving mechanism is perhaps the most perplexing problem related to plate tectonics. The mechanism must be compatible with the rigid behavior of lithospheric plates, and with a wide range of plate sizes, shapes and motions. It must be consistent with complex configurations of plate boundaries and equally complex boundary interactions, such as the destruction of ridges at subduction zones. The objectives of this paper are to show that plate velocities can be predicted and that directions of absolute plate motions are apparently related to temperature gradients, and to point out that the notion that plates tend to move down horizontal temperature gradients under the influence of gravity offers plausible explanations for other phenomena which have not been explained previously.