Big History Spotlight: Juan Carlos Afonso
Big History Spotlight: Juan Carlos Afonso
Dr Juan Carlos Afonso is based in the Department of Earth and Planetary Sciences and works with the GEMOC ARC National Key Centre. His research focuses on geophysics and geodynamics, and spans many different geophysical processes. Dr. Afonso is also a contributor to the Opening REAL Science Project. Read more about his work in the profile below, and check out his web page here.
What is the current focus of your academic work?
My current research integrates different disciplines such as mineral physics, petrology, geodynamics, lithospheric modelling, nonlinear inversion, and thermodynamics, to explore and improve our understanding of plate tectonics (yes, it's a lot of fun!). More specifically, I am interested in the evolution of the lithospheric mantle, the mechanical and geochemical interactions between tectonic plates and the sublithospheric mantle, and their effects on small and large-scale tectonic processes. The lithosphere is critical to humans because it is the reservoir of most of the natural resources on which modern society depends, as well as the locus of important geological and biological process such as seismic activity, CO2-recycling, mineralisation events, and volcanism.
During the past few years I have developed a multidisciplinary approach that gives insights into lithospheric stability, its thermal structure and possible compositional fields. This knowledge not only helps us understand the evolution of lithospheric plates but its outcomes are directly translatable into predictive exploration methods for the energy sector.
Could you briefly explain the breakthroughs you have had in your work with plate tectonics?
The European Geoscience Union has recently highlighted the work I did on combining different geophysical, geodynamic and geochemical datasets into a single conceptual framework that has become known as the "LitMod approach". This theoretical and computational framework fully integrates geochemistry, mineral physics, thermodynamics, and geophysics in an internally-consistent manner and allows researchers from different (disciplines seismology, geodynamics, petrology, mineral physics, etc.) to construct models of tectonic plates that not only satisfy one particular set of observations, but a multitude of observations. This is of primary importance because it guarantees consistency between theories and models (i.e. you can't cheat!), and results in better and more robust data interrogation and interpretation. This approach is being applied to a wide range of geodynamic and geophysical problems, from studying the water content of the Earth's mantle to inferring the thermal structure of Venus.
More recently, my colleagues and I presented the idea of multi-observable probabilistic tomography, a technique that is similar to CAT-scanning in medicine, but that we used to study the thermochemical (or thermo-chemical-mechanical) structure of lithospheric plates and upper mantle. We showed that it is a feasible, powerful and general method that makes the most out of available datasets and helps reconcile disparate observations and interpretations. This unifying framework brings researchers from diverse disciplines together under a unique holistic platform where everything is connected to everything else and it will hopefully help understand the workings of the Earth in a more complete manner. But there is a lot of work yet to be done to achieve this!!
What attracted you most to the study of geophysics?
My first inspiration was my father, who always had a theory for how natural processes work (and still has!). He inspired me to learn more about the planet we live in, where we come from, and to question everything. At the same time, I was always attracted to quantitative explanations of natural processes. I was never really satisfied with stories about how things work. I remember sitting in Geology classes and listening to the nice "stories" about how glaciers move, how mountains are built, how the interior of the Earth's is in constant motion.
But what I really wanted to understand was the quantitative aspects of these processes (the magnitude of the forces involved, the root causes for them, etc) and to be able to model them and make predictions, etc. I used to tell to my university lecturers that if we could not model it in a computer we did not really understand it. Later in life I found out that the great physicist Richard Feynman had said something similar many years before I was born ("What I can't create, I don't understand"), so now I quote him all the time!
My second inspiration, and what really crystallise the idea of becoming a geophysicist, came after reading the book "Rheology of the Earth" by Giorgio Ranalli when I was at uni. I became so obsessed with understanding everything in that book that I ended up doing my PhD under Giorgio's supervision. We remain great friends until today.
How is the field of geophysics changing?
A colleague recently said "Each single discipline within the geosciences has progressed tremendously over the 20th century; the problems now lie at the interfaces between the sub-disciplines and ensuring that all geoscientific data are honoured in integrated models. We are well beyond the time when scientists can present their interpretations based on mono-discipline thinking. We absolutely must think of the Earth as a single physico-chemical system that we are all observing with different tools." These sentences capture very well the driving force behind a new revolution in Geophysics.
The new generations of geophysicists are becoming increasingly more interested in understanding the Earth as a complex, "living" physical entity rather than a static object described by "stiff" physical parameters such as mean density, coefficients of thermal expansion, etc. And when we pay attention to these complexities, to the great variety of links between physical and chemical processes within the Earth (and on the surface!), we start realising that the boundaries between traditional disciplines such as geophysics, experimental petrology, geochemistry, etc are nothing more than semantics.
Geophysicists are starting to realise the importance of working under a more holistic framework. Of course, the ever-increasing quantity and quality of global datasets (satellite-derived gravity, global seismic arrays, etc) plays an important role, as they provide the necessary data to derive models of the Earth. We still see models of the Earth derived from a single dataset that are incompatible with other observations. Some are better, some are worse. To have a model that explains all observations does not imply that the model is correct, but it does minimise the chances of being wrong! Plate tectonics and science in general use this concept to advance our knowledge of the Earth.
What advice would you give to students looking to pursue geophysics and/or geodynamics professionally?
Go for it!!! You will not regret it! It is a truly all-embracing discipline that allows you to pursue your own interests, whatever they are. Whether you like chemistry, or physics, or mathematics, or you are interested in global warming, geophysics will give you the tools to understand these processes and make informed decisions... and the future generations will have to make some tough decisions regarding our planet! All you need is to want to discover how the universe works!. Incidentally, geophysicists are very-well paid in the industry sector... ;)
How could Big History be applied within your field?
One of the biggest challenges for Earth Science students is to get an appreciation of the time scales involved in geological processes. This is not only of academic importance, but a fundamental prerequisite to understanding how the Earth works, how we humans interact with our planet, and therefore how we can deal with natural hazards, manage natural resources, and protect our environment. Interestingly, recent studies in climate science, geology, archaeology, anthropology, and history have concluded that the correlation between the "random" episodes in geoscience (e.g. volcanism, ocean current oscillations, seismicity, fluctuations in solar output, etc.) and the timing of major events in human history are statistically significant. Although the actual causes for such correlations may be difficult to isolate, they clearly imply a close connection between humanity and geoscience that too often is overlooked in geophysics courses. As American poet Will Durant put it: "Civilization Exists by Geologic Consent...subject to change without notice". Big History is the perfect platform to deliver this appreciation for "natural time scales", the role they play in human history, and on the development of ideas about our planet.