Prof Hugh O’Neill

Evaluating the chemical composition of the Bulk Silicate Earth

The chemical composition of our planet, Earth, is the essential starting point for understanding how it formed, differentiated and evolved. For example, what are the concentrations of the “Heat Producing Elements”, Th, U and K, the radiogenic heat from which help drive the plate-tectonic cycle? Why has the Earth been able (with the help of early life) to produce an oxygen atmosphere conducive to the development of higher organisms? What aspects of the composition may be pre-requisites for life elsewhere, and how special are these aspects? Constraining the Earth’s composition requires a number of theoretical assumptions combined with a lot of geological, geochemical and geophysical observations, and brings together many branches of “Geology”, construing the subject in the broadest sense.

I shall describe briefly how current estimates of the Bulk Silicate Earth composition have been arrived at, and then discuss possible errors and uncertainties in this paradigm, and where future improvements may come from.

Biography

Hugh O’Neill is an earth scientist whose career has focused on experimental petrology and geochemistry — the study of the composition of rocks, their minerals, and how they came to form. His work has been crucial in advancing our understanding of how rocky planets form, and how the detailed study of Earth materials can solve large-scale geological problems.

He has greatly improved our understanding of key questions relating to our planet, including: the chemical composition of Earth and how it differs from other planets; the origin of the Moon; and the history of Earth. His work stands out due to his use of careful laboratory measurements to address big problems.

Hugh is an Australian Research Council Laureate Fellow at the Research School of Earth Sciences (RSES), the Australian National University — one of the foremost research groups worldwide concerning experimental investigation into deep Earth petrology. As well as being a Fellow of the Royal Society, he is a Fellow of the Mineralogical Society of America, the Geochemical Society and the Australian Academy of Sciences.