The Canadian geophysicist John Tuzo Wilson (1908-1993), professor at the University of Toronto, helped completing the picture. By the end of the 30s, Wilson met Hess in Princeton, where he was working at his doctorate program. Hess’ ideas fascinated him deeply. Wilson contributed to the development of the Plate Tectonics theory by confirming Diez’s studies on the Hawaiian hot spot.

But Tuzo Wilson is renown for having described a third type of plate margin, which connects ocean rifts to ocean tranches: the transform margin. Ocean ridges appear displaced by long fracture zones almost perpendicular the the rift axis.

Wilson suggested they were a particular kind of strike-slip faults, faults with horizontal displacement. Their peculiarity, apart from being a plate margin, is they are seismically active only within the portion between the two sectors of rift they dislocate. This because it is the only portion along the transform faults where the lithosphere is moving in opposite directions.

Actually, the real transform fault is just the portion between the two rift segments. Outside it is just a fracture zone, no relative motions.

The infamous San Andreas fault in California, the one who inspired Herny Reid‘s elastic rebound theory and the fault displacement, is an example of transform fault whose movement has been transmitted to continental crust: The North American plate as it moves to the west is overriding the Pacific Plate, so underlying transform fault displacement has propagated to the surface, resulting in the right-lateral strike-slip fault movement between the two sectors of Pacific mid-ocean ridge

Tuzo Wilson also gave the name to the Wilson Cycle, which describes how the Earth’s continent are continuously aggregating and separating because of tectonic motions.