50 Years Ago Today in Geology…

Fifty years ago the world looked very different to geologists. Not only was most television still in black and white, but the Grand Unifying Theory of Plate Tectonics had not yet been unified.

It was still a network of ideas that would converge by the end of the 1960s into the conceptual model of the Earth we know today: distinct chunks of Earth’s rigid outermost layer move over the more malleable mantle below, with complex interactions at the chunks’ edges.  The fact that tectonic plates exist and move has become as familiar as color TV at home, but that was not always the case.

Today marks the 50th anniversary of one of the seminal publications that changed the way we see the world.  The author, Canadian Geophysicist John Tuzo Wilson, grew up at the forefront of global change culturally, politically, and scientifically.  His big-picture thinking and international experience allowed him to pull together many observations and weave them into descriptions of the workings of our planet.  Some of his big ideas turned out to be wrong; others continue to be supported by modern findings with much more advanced research tools.

What Wilson published exactly 50 years ago today was one of his less famous but still paradigm-setting contributions: his conceptual model for opening and closing of oceans.  Alfred Wegener had already suggested in the early 1900s that continents move around the surface of the earth, specifically that there had been a super-continent (Pangaea) where now there is a great ocean (the Atlantic).  In his paper called “Did the Atlantic Close and Then Re-Open?” (published in Nature, 13 Aug. 1966), Wilson explained the geological evidence that North America and Europe were once separated across an ocean before the Atlantic Ocean.  This ocean closed in stages as the continents that used to be separated by the ocean converged by subduction and eventually collided in a mountain-building event.  The combined continent was then sliced apart and the continents drawn away from each other once more as the modern Atlantic Ocean opened.  The paper combined the nascent ideas of divergent and convergent plate boundaries into a conceptual model that matched observations of geological features around the world.  The tectonic cycle he described now goes by “the Wilson Cycle” or the “Supercontinent Cycle” and still governs how we think of the evolution of tectonic plates through time.

One way we can study the evolution of tectonic plates and their motions is by investigating the seafloor!  Right now, the JOIDES Resolution is doing exactly that!  The sediments we collect from the seafloor—thousands of kilometers away from where they were eroded from land—can tell us about how the Himalayan Mountains grew, about when volcanoes in Indonesia erupted before people recorded their history, and how the Indian Plate and Sunda Plate have interacted in the past and how they might in the future.

Further Reading:

Delightful 2-page biography by the Geological Society of America: http://www.geosociety.org/gsatoday/archive/11/9/pdf/i1052-5173-11-9-24.pdf

Character sketch in a series about Pioneers of Plate Tectonics from the Royal Geological Society (UK):  https://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/John-Tuzo-Wilson<

The paper itself, whose ideas generally still hold though details have been revised by more recent studies: Wilson, J.T., 1966, Did the Atlantic close and then re-open?:
Nature, v. 211, p. 676–681. http://www.nature.com/nature/journal/v211/n5050/pdf/211676a0.pdf<

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