Plate Tectonics – When, Why and How?

by Craig Storey

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A recent meeting at the Royal Society in London called “Earth Dynamics and the Development of Plate Tectonics. Above are (some of) the Portsmouth Crustal Evolution Research Group enjoying the debate.

It was a really lively 2 day meeting with representatives from as far as USA and Australia, picked to give their perspective on different issues. So we went from other planets (Venus and Mars) to the building blocks of our own planet, with a great talk from Maud Boyet (a certain class of enstatites can resolve BSE trace elements and a range of stable isotopes – but not major elements!). Geodynamics was a major topic of discussion, with input from numerical modellers and experimentalists and, of course, debate from geologists on the veracity of the models. An excellent summary of the geochemical and isotopic evidence for the growth and reworking of the continental crust was given by some familiar names to this group – Tony Kemp, Peter Cawood and Bruno Dhuime. A lively debate followed a presentation by Jun Korenaga, reexamining the famous crustal evolution growth curve models and proposing something controversial. The claim was based on the model representing the mantle evolution (Nd isotopes in basalts) rather than the crusal record (Hf and O in zircons). However, it would be nice to know if the Nd record presented stands up to scrutiny. Some very engaging talks on links between geodynamics and the atmosphere and biosphere kept spirits up, with Cin-Ty Lee talking about continents and their control on climate, Aubrey Zerkle introducing us to the idea of “Biogeodynamics” and giving a great talk on her work on the nitrogen and phosphorous cycles, and finally Tim Lyons illuminating us on the Proterozoic, the rise of oxygen and the possible tectonic links to climate and life. Bob Stern finished up with a summary discussion and then we all went home for jelly and ice cream.