John Tuzo-Wilson (1908 - 1993)

The Canadian geophysicist John Tuzo-Wilson was initially sceptical of the theory of Plate Tectonics, but eventually became one of its most famous supporters, proposing two important ideas.

While evidence for Continental Drift was mounting, the theory still hadn’t explained why active volcanoes are found many thousands of kilometres from the nearest plate boundary. In 1963, Tuzo Wilson proposed that plates might move over fixed ‘hotspots’ in the mantle, forming volcanic island chains like Hawaii.

In 1965, he followed this discovery with the idea of a third type of plate boundary - transform faults. Also known as a conservative plate boundaries, these faults slip horizontally, connecting oceanic ridges (divergent boundaries) to ocean trenches (convergent boundaries) Transform faults were regarded as the missing piece in the puzzle of plate tectonic theory. They allowed for plates to slide past each other without any oceanic crust being created or destroyed. The most famous example is probably the San Andreas Fault between the North American and Pacific plates.

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