Features / History

#PlateTecStories: Shifting theory at the Royal Institution

A guest blog from The Royal Institution

The Royal Institution (By Gryffindor – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14730818)

The Royal Institution has been at the forefront of science communication in the UK since it was founded in 1799. We are a charity that has allowed communicators from around the world to come, speak and educate about the science that has helped to shape our lives, culture and the world around us. We have achieved this in a number of ways, through general public lectures, ‘Friday Evening Discourses’, Christmas Lectures and in recent years, award winning digital films and animations. All of these tools have been used to communicate the science and importance of the story of plate tectonics.

A relatively young theory, based on an idea developed in the early 20th century by German meteorologist Alfred Wegener, plate tectonics relies heavily on the use of modelling to demonstrate the concept of continental drift.

The most significant lecture given at the Ri on this fascinating topic was a Discourse which took place in 1963, given by a young physics professor from the University of Newcastle upon Tyne, S.K. Runcorn, who delighted the gathered audience with his contribution to the theory.

Keith Runcorn (far left) with William Bullerwell, Dan McKenzie and members of the Chinese Academy of Sciences. c Geological Society (archive reference LDGSL/1107/C/5)

Runcorn began to study aspects of the Earth’s magnetic field while at University of Manchester undertaking his PhD in the 1940s. He soon developed an interest in palaeomagnetism, the study of the residual magnetisation that is evident in ancient rocks. Runcorn’s analyses of rocks in Europe provided evidence of periodic reversals of the Earth’s field (geomagnetic polar reversals) over geologic time. His data suggested that the Earth’s north magnetic pole had moved and wandered across the planet over hundreds of millions of years.

Royal Institution Proceedings – How the Continents Drift_SK Runcorn 1963 page 1

Runcorn’s heavily illustrated lecture was based on his previous years of research. In it he outlines Wegener’s original hypothesis that the continents had once been grouped into two land masses of Laurasia and Gondwanaland and the limited evidence that Wegener had to his hands at the time. Delving into the subject he comments on the latest research and explains that the continents float on the mantle of the earth.

‘To displace the continents over thousands of kilometres, it is necessary to postulate flow patterns of similar dimensions in the mantle. Convection could be caused by the heating of the Earth’s interior by radioactive decay or by the release of energy by chemical separation, the heavier elements moving to the centre and the lighter silicates moving upwards to the continents. Probably both processes contribute to the convective motions. There will be a tendency for the continents to move towards the places where the flow is descending and for the ocean basins to be over the rising columns. This patter seems at the present time to be in accord with the observations that have been made of the world wide oceanic ridge system.’

The mapping of the first oceanic ridge in the Mid-Atlantic was undertaken by Marie Tharp who is the subject of a Ri animation voiced by Helen Czerski. This short film describes the pioneering work of Tharp who transformed a barren and flat ocean floor into a three-dimensional space with valleys, trenches and mountains. This vital work helped provide key clues in supporting the theory of continental drift.

 

By the Ri’s 1995 Christmas Lectures given by Dr James Jackson entitled ‘Planet Earth, and Explorer’s Guide’, the theory of continental drift was well established. Jackson explained the theory in lecture 4 of the series; The puzzle of the continents. The lecture then went on to state that although plate tectonics is good at describing what happens on the ocean floor and the changing distribution of the continents, it does not help to describe what happens when the continents themselves deform.

Professor James Jackson speaking at the Geological Society’s ‘Plate Tectonics at 50’ meeting in October 2017.

James Jackson’s 1995 Christmas Lecture series will be available to watch later in the year on the Ri website, where the entire catalogue of known recorded lectures are being uploaded.

Runcorn, Czerski and Jackson are just a few scientists who feature in the ongoing story of plate tectonics. It is still an area of intense study today adding insight into how the planet was formed. Runcorn ended his Discourse by stating ‘by studying the ancient magnetic field of the earth, the geophysicist has a powerful method of investigating quite fundamental questions concerning the origin of the earth. In particular the interesting problem of whether the Earth began as a cold or hot body should finally be resolved.

The Royal Institution

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