In 1967, Jason Morgan offered a groundbreaking paper on the annual assembly of the American Geophysical Union (AGU) in Washington DC. It confirmed that Earth’s floor consists of a couple of dozen inflexible plates. They’re created at mid-ocean ridges, destroyed in subduction zones the place they converge, and transfer previous each other alongside nice faults, such the San Andreas Fault in California. Different papers adopted, explaining that volcanoes happen the place plates subduct, mountains rise the place and when continents collide, and earthquakes end result from jostling and shearing at plate margins.

Inside a decade, the idea of ‘plate tectonics’ was broadly accepted. Morgan had offered the geological equal of Charles Darwin’s principle of evolution quickly after being appointed as an assistant professor at Princeton College in New Jersey and had reworked geology ceaselessly. He has died aged 87.

Morgan was born in Savannah, Georgia. After secondary college, he fell in love with physics on the Georgia Institute of Expertise in Atlanta. He spent two years within the US Navy as an teacher on the Naval Nuclear Energy College in New London, Connecticut, earlier than shifting to Princeton to review for a doctorate within the physics of relativity with Robert Dicke. After acquiring his PhD in 1964, he turned a postdoc within the geosciences division, the place he was promoted to assistant professor in 1966.

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Dicke was within the drive of gravity and, specifically, whether or not the ‘gravitational fixed’ (G; a basic parameter in gravitational principle) was truly fixed. If this drive weakened, Earth would increase like a balloon. He tasked Morgan with in search of proof of this within the sample of earthquakes throughout Earth, which Morgan was learning to seek for geophysical indicators of gravitational waves. Harry Hess, the chair of the geosciences division, had mapped the topography of the ocean flooring and found mid-ocean ridges — the nice chain of submarine mountains that wraps itself twice across the globe just like the seams on a baseball. He had proposed that new crust kinds on the ridges and strikes away, a mechanism referred to as sea-floor spreading. Ultimately, earthquakes supported Hess’s concepts and the idea of plate tectonics a lot better than they did Dicke’s balloon speculation.

In the meantime Fred Vine, a graduate pupil on the College of Cambridge, UK, had found that the ocean crust is magnetically striped: Earth’s magnetic subject modifications polarity, the north pole turning into the south pole and vice versa, on timescales from tens of hundreds to tens of millions of years. The route of the magnetic subject is frozen into the ocean flooring when the ridge lavas cool and unfold, producing stripes parallel to the ocean ridges — confirming Hess’s concept. Hess employed Vine and gave him a desk in the identical workplace as Morgan. Though the pair didn’t publish collectively, a long time later Morgan advised Quanta Journal that, of the many individuals who contributed to the idea of plate tectonics at Princeton, “the one that was most useful for me was Fred Vine”. Vine and his Cambridge supervisor Drummond Matthews are properly acknowledged for the contribution that their magnetic research made to the invention of plate tectonics.

Remembering the spherical trigonometry he had learnt in school, Morgan knew tips on how to outline the movement of the plates — as rotating round fastened factors or ‘poles’ on a sphere. The poles may change sometimes with time, however the interiors of the plates didn’t deform. His mannequin defined all of the observations. Thus, all of geology might be summarized with astounding class. He offered his findings in his 1967 AGU speak and a subsequent paper, each entitled Rises, trenches, nice faults, and crustal blocks (W. J. Morgan J. Geophys. Res. 73, 1959–1982; 1968).

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Morgan’s second essential contribution to geophysics was in investigating convection within the mantle, Earth’s scorching, fluid inside, and addressing what made plate motions doable. He interpreted chains of volcanoes when it comes to poles and plate rotation, a spectacular instance being the Hawaiian Island chain of volcanoes. An abrupt bend within the chain close to Halfway Island signifies that the adjoining plates had reorganized about 40 million years in the past.

Morgan proposed that these volcanic chains have been tracks — when scorching upwellings within the mantle (known as plumes) method the floor, they set off volcanism within the plate above it. Because the plate strikes, linear chains of volcanoes are produced. As a result of the plumes don’t transfer a lot, the historical past of plate movement could be inferred from these tracks. Morgan additionally made laptop fashions — an modern method on the time — that in contrast the place the tracks needs to be theoretically to the place they have been geologically. All of the proof was in step with inflexible plates shifting over a hard and fast set of plumes.

Jason spent his complete profession at Princeton, residing on campus together with his household and retiring in 2004. He spent his final years residing outdoors Boston as a visiting scholar at Harvard College in Cambridge, Massachusetts. Jason was awarded the Nationwide Medal of Science in 2002, and lots of different awards. It might be truthful to say that nobody in latest occasions has contributed extra to understanding geology, and he did so with such modesty. Jason all the time had time to speak and assist; he was remarkably considerate, and a extremely efficient trainer. You needed to be conscious that it might take him a minute to reply when conversing, and needed to wait patiently for his reply. However his response was all the time well worth the wait.

Competing Pursuits

The writer declares no competing pursuits.