What is a fault, and how does the existence of faults support the theory of plate tectonics?​

“Many of the objections are long standing but apparently unknown to many geophysicists, while some are peculiar to the new global tectonics. The conclusions drawn, in order of probability, are (1) the continents have almost certainly not moved with respect to each other; (2) convection is not active throughout the whole mantle; (3) even if convection is active in the upper mantle it cannot account for drift; (4) pole positions derived from paleomagnetism, and results of this method of investigation in its global form generally, are afflicted with an unknown cause of error and are in any case too inexact for drift reconstructions.”

(Wesson, 1972)