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Geodynamics

Geodynamics

The Sassy Scientist – Managing Monsters

The Sassy Scientist – Managing Monsters

Every week, The Sassy Scientist answers a question on geodynamics, related topics, academic life, the universe or anything in between with a healthy dose of sarcasm. Do you have a question for The Sassy Scientist? Submit your question here.

Aminta asks:


How do you deal with bad co-authors (i.e. people who make writing papers more complicated and unpleasant than it needs to be) that are also senior scientists?


Dear Aminta,

Annoy them as much as possible. Relentlessly, but politely. Haunt their dreams. In case they are located within the same university, don’t just start emailing them willy-nilly. You can do so much more. Knock on their door every single day. Invite them for a coffee or join ‘em for lunch. Use casual conversations to fortuitously steer the topic towards your manuscript. Conveniently leave the office at the same time as your co-authors and come back in the morning when they do. Simply butter them up as much as possible, without presenting yourself too needy or a suck-up. It should be their idea to respond quicker to your requests. For those not in your institution, other rules apply. Try to set deadlines several weeks in advance of your actual goal, and up the ante in terms of email check-ins the days building up to their deadline.

Trust me. This is the only way that may turn out fruitful. I’ve tried to cross the only other path: patience. Just utter patience. Problem being that you cannot actually do that much. You’ll end up frustrated anyway. Tread carefully though; if your co-authors have some big toes and cannot be too bothered with your progress, the best way is to simply wait and see. A long wait may result in a finalized manuscript, while a short wait will result in tears. There are three grades of co-authors; 1) happies [quick responders with real constructive comments], 2) fickles [oftentimes tardy with the same comments on repeat], and 3) grumpies [no explanation needed]. Your job is to push every co-author into that first grade by smooching and appearing to be interested in whatever they’re up to. Preferably done before you start writing a manuscript. Remember that you do actually need them. Turn that frown upside down and start grinning like a Cheshire cat.

Yours truly,

The Sassy Scientist

PS: This post was written with some sore cheek muscles.

Adaption

Adaption

As temperature records have continuously been broken all over the world, many of us scientist had to endure extreme conditions in our overheated offices. Climate change is happening, and faster than we’d like to think, but how does this play a role in the scientific community? In this week’s blog post, geodynamicist Nicolas Coltice (professor at Ecole Normale Superieure de Paris) shares his passionate opinion on the matter and sheds light on several important topics that may easily be overseen by enthusiastic scientists. 

 

Nicolas Coltice is a professor in the Laboratoire of Geology of Ecole Normale Supérieure de Paris.

I took my last flight for work in May 2017 to go to a meeting of the Deep Carbon Observatory in Moscow. I had started evaluating my carbon footprint a couple of years before, and flying to do science on carbon questioned me. The first flight I ever took was when I was about 14, to go to a place close to Chernobyl (in the U.S.S.R. at the time), a few years after the catastrophe. It seems that Russia brings me back to environmental questions. In the context of climate change today, many scientists give their opinions on the future. Civilization will collapse, or science will magically save us all. There is so much abstract agitation and noise in the debates. Both the exploitation of nature and pollution impact landscapes and the living so quickly. What will the world be like in 30 years? Who can guess rationally?

 

Climate countdown

When I started to write this blog post, it was June 13th. The temperature in Delhi was about 48°C and the Monsoon did not seem to start. Water shortages led to fights with people being killed. In Poland, temperatures reached over 30°C. But in France, temperatures were cooler and close to those occurring in Greenland. A few weeks later, we had the highest temperatures ever recorded in the South of France. Particles and pesticides are all over the place and we eat and drink litters of them every year. Climate will continue to change: even if we stop emitting carbon and methane, the ocean will keep on doing so for centuries.

 

Surface temperature of some European countries on June 27th 2019 (European Space Agency).

 

The IPCC and diverse agencies have given a very simple recommendation: by 2030, we have to lower our carbon emissions by 50%. That is 11 years from now, soon to be 10, soon to be 9… In the next 10 years, there is minimal chance that humanity has developed new energy sources for the billions of people all over the world. For example, building a nuclear power plant takes years, and it can only distribute energy about 10 years after completion. Besides blaming politics and big companies, what can one do here and now? Because the shift of society does not seem to start in comfortable offices, it has to start everywhere. It is now. What actions can we take as geodynamicists? In geodynamics we tackle problems with a large vision, including long-range dependencies, evaluating the forces at play.

Because the shift of society does not seem to start in comfortable offices, it has to start everywhere.

I started to think about our job as a scientist. Many carbon footprint tools help us identify how to mitigate our carbon emissions. The Tyndall Center for Climate Change Research proposes guidelines for low-carbon research, that are quoted here: ”

    • Monitor and reduce. I will keep track of the carbon emissions of my professional activities, and set personal objectives to reduce them in line with or larger than my country’s carbon emissions commitments (…).
    • Account and justify. I will justify my travel considering the location and purpose of the event, my level of seniority, and the alternative options available.
    • Prioritise, prepare and replace. For activities that I organise, I will choose the location giving high priority to a low carbon footprint of travel of the participants, and I will encourage, incorporate and technically support online speakers and webcasts to reduce unnecessary travel.
    • Encourage and stimulate. I will resist my own FOMO (Fear Of Missing Out) from not attending everything and work towards sensitizing others to the need of the research community to walk the talk on climate change.
    • Reward. I will work with my peers, Institute and Funders to value alternative metrics of success and encourage the promotion of low-carbon research as a realisable alternative to a high-carbon research career.”

The Tyndall Center for Climate Change Research also provides a Travel Strategy (link to PDF) that aims to help individual researchers to reduce their emissions through time.

Emit carbon or perish

This is essentially dealing with travel, clearly the main source of scientists’ carbon footprint. Let’s identify the forces at play that make us using tons of carbon every year on average. I identify a major shift in our practice between 2000 and 2010, with digital doping of the old “publish or perish”. It would be easy to blame computers. Private companies build publication databases with our work to compile performance indicators of individuals. Now a handful of business groups own most of the journals, questing increasing financial profit (Elsevier and Springer operated a better profit margin than Apple in 2014, 37% and 35% respectively). What was common (not state-controlled but controlled by the scientific community) became increasingly private and marketable. Growth of publication numbers generates billions of euros of dividends for stakeholders, at the expense of public money. Every year subscriptions cost more to the scientific community (see for instance the website of the University of Virginia Library). And we are now productive workers in a globalised science-market. It is for granted that competition is the source of good science… or in any case good money. Therefore, scientists have to publish more, be everywhere to “sell” their results or see which ones they “buy”, and hence travel all over the world.

Journal and articles figures for 2018 by the STM association. Profit data for the Scientific, Technical & Medical division of Reed-Elsevier only (Larivière et al., 2015) .

 

Competition-strategy modifies the science itself, introducing loss of integrity (Fanelli, 2010), and of course dramatically increasing our environmental impact. We are pushed to acquire the most powerful machines, generate the biggest datasets, do large-scale analysis, publish as many papers as we can, and travel the world to disseminate the results. Or perish. Bigger machines often require less energy to obtain the same performance as the old ones. However, the energy gain of new technology becomes more than compensated by accentuated use of it. This is the rebound effect. New technology is not a substitute but an addition. Hence we need more energy and more natural resources. Can we substitute instead of add? Can we identify when it is so easy to use machines instead of our brains, but somewhat irrelevant to do so?

Scientists have to publish more, be everywhere to “sell” their results, or see which ones they “buy”, and hence travel all over the world.

Although planes are getting more carbon-efficient, travel for science has become intensive. Some colleagues like their job because they can travel, which I understand. The number of conferences and workshops exploded. The increase in attendance of worldwide meetings like AGU (11,422 attendees in 2004 and 21,702 in 2012) questions their role in terms of scientific relevance and impact on the planet. What shall we do with all these gatherings? Mobility looks like a necessity today. However, research has shown that limiting the use of planes to travel has barely any impact on scientific careers (Wynes et al., 2019).

(Lower-carbon) Science as a common

Competing, publishing as much as possible, privatising science and transferring public money to the stakeholder of publishing groups constitute a dead-end for our job. This is a dead-end for science. This is a dead-end for knowledge and humanity. Exponential growths of h-index, publication rates, data collection and conference travel are not sustainable. The rebound effect often kills the gain of progress for production gain. Can we make a transition as a community, building our commons and collaborative organizations? Can we start to teach new research ethics and practices so the new generation will be ready to do this job in a sustainable way? We have 10 years, soon to be 9.

 

Larivière, V., Haustein, S., and Mongeon, P. (2015). The Oligopoly of Academic Publishers in the Digital Era. PLoS ONE 10(6): e0127502

Fanelli, D. (2010). do Pressures to Publish Increase Scientists' Bias? And Empirical Support from US States Data. PLoS ONE 5(4): e10271

Wynes, S., Donner, S. D., Tannason, S. and Nabors, N. (2019). Academic air travel has limited influence on professional succes. Journal of Cleaner Production 226: 959-967

The Sassy Scientist – Pull The Plug, Or Persevere?

The Sassy Scientist – Pull The Plug, Or Persevere?

Every week, The Sassy Scientist answers a question on geodynamics, related topics, academic life, the universe or anything in between with a healthy dose of sarcasm. Do you have a question for The Sassy Scientist? Submit your question here.

Georgia asks:


One of my friends recently left the PhD program with some severe emotional and motivational issues. I’m having doubts too. What shall I do?


Dear Georgia,

It’s the summer holidays. No more teaching duties. A lot of his colleagues are out of the country. Even his office mate is gone hiking in some mountain range no-one has never heard of. “Preferring that solitude over my company”, he murmurs as he slouches behind his computer. Blue skies outside. No sunshine in this office; there’s a dark cloud stuck inside. A whirling fog of desperation. Bashing away at the keyboard, heaving at the sight of failure. It hasn’t worked all morning. “Just like last week. Just like last month”, he sighs. The music might as well be turned off. Even Sweet Caroline can’t push his spirits today. Time for a coffee. Oh yeah … out of order, that’s right. ‘Cause maintenance is also off-duty. Why not? It’s not like anyone’s working to a deadline. Returning to work, the only sound piercing the airy silence is a fly. Buzzing carelessly towards an empty mug. Two souls in a square, concrete dungeon of solitude. Scratch that … only one left. The fly did not return from its journey. Wondering what that would feel like, he hears a noise outside. His heart beat increases as he recognises the waddle. That’s his supervisor! In his eyes a glimmer of hope returns. Maybe she has some ideas to fix all problems. She’s always so busy with the other students, but they’re all away now. “I’am the only one. She must come to talk to me!”, he concludes. He sits up straight, closes emails and puts away his phone. There she comes! Just a couple more steps.…. No! What’s she doing? She hurdles past his door, straight into the bathroom. “Why do I even bother? She’s not coming back”, he groans disappointed. She never does. How much longer ‘till this dream of a research project is over? Not so much a dream as it has become a waking nightmare…

I suppose you recognise this sentiment, don’t you? Unfortunately, an increasing number of your colleagues also intersperse their daily work routine with such day dreams. Well, that’s what I presume considering the increasing amount of articles in Nature about mental health and depression over the past two years. Fairly recent studies by Levecque et al. (2017), Evans et al. (2018) and Sverdlik and Hall (2019) even suggest a “mental health crisis”, especially for PhD students (Sohn 2016, Woolston 2018) but also beyond this stage (Reay 2018). I’m certain that by now you’re thinking: “You must be talking about people in the humanities or (bio)medical sciences. I never noticed anyone in geodynamics slip into a depression”. Well, that’s exactly the problem. Even though you’re a “good scientist” when working 14 hours a day, including the weekends, check and answer your email ’til the early hours and attend as much conferences as you can, something may not be that good: your state of mind. The constant pressure to perform so that you can stay in science, and an environment of “strong personalities” provide the perfect ingredients for a swirling depression cocktail. Who needs help, right? We can manage ourselves. The shrinks can stay in their own lane.

So, why has mental health become an increasing problem in science then? Why do you have doubts? I mean, didn’t these problems exist a couple of decades ago, when the people now in charge of the research groups, universities and funding agencies started their own careers? Are you part of a PhD pool that has grown to include a majority of snowflakes who are not able to handle setbacks, rebuffs and hard work? I doubt it. Maybe the current generation of PhD’s is not managed well enough by their supervisors that are too focused on their own career to also consider the various needs of their (sometimes too many) PhD’s and post-docs. Conversely, the aptitude to (be brave enough to) ask for help may also be lacking. I mean, who wants to work with someone in doubt of their own career, who cannot even manage to comfortably meet the deadlines set by their supervisor? Well, you’re clearly way too hard on yourself. Recognising that you’re not doing well (mental health-wise) is actually a strong point; you evaluated your own well-being and came to the conclusion that something wasn’t right. I can only applaud such self-awareness and hope you’ll find a way to fight the demons. You shouldn’t leave science. Persevere, please. Have you spoken to direct colleagues or your supervisor about your doubts? Too afraid? Just do it. Usually (and there are exceptions of course) scientists are fairly social creatures, willing to help their students in any way they can. The cynical side of this is that it is also in their own best interest as you must not forget: you not making it is a stain on their record.

Whilst you’ve been brave enough to ask for help (even though it’s just little old me), the harsh reality is that you’re not alone. So, to finish this endlessly positive story, I can only ask for one thing: talk to each other. Check in on those hermits that have locked themselves away in their office or lab, and who ‘can’t talk, busy’. Reach out to the senior staff (and maybe even HR) because it’s way too late when they find out you’re having difficulties when you’re stuck at home with a major depression or have a mental breakdown in the middle of a lecture room. Not great for them, slightly worse for you. Talk people, we’re usually much better at it.

Yours truly,

The Sassy Scientist

PS: This post was written in a square, concrete dungeon of solitude.

References:
Evans, T.M., L. Bira, J.B. Gastelum, L.T. Weiss, N.L. Vanderford (2018). Evidence for a mental health crisis in graduate eductions, Nature Biotechnology, 36, 3
Levecque, K., F. Anseel, A. De Beuckelaer, J. Van der Heyden, L. Gisle (2017). Work organization and mental health problems in PhD students, Research Policy, 46, 868-879
Reay, D. (2018). You are not alone, Nature, 557, 160-161
Sohn, E. (2016). Caught in a trap, Nature, 539, 319-321
Sverdlik, A., N.C. Hall (2019), Not just a phase: Exploring the role of program stage on well-being and motivation in doctoral students, Journal of Adult and Continuing Education, 0, 1-28, doi:10.1177/1477971419842887
Woolston, C. (2018). Why mental health matters, Nature, 557, 129-131

What controlled the evolution of Plate Tectonics on Earth?

Great Unconformity - Immensity River, Grand Canyon
Stephan Sobolev

Prof. Dr. Stephan Sobolev. Head of the Geodynamic Modelling section of GFZ Potsdam.

Plate tectonics is a key geological process on Earth, shaping its surface, and making it unique among the planets in the Solar System. Yet, how plate tectonics emerged and which factors controlled its evolution remain controversial. The recently published paper in Nature by Sobolev and Brown suggests new ideas to solve this problem….

What makes plate tectonics possible on contemporary Earth?

It is widely accepted that plate tectonics is driven by mantle convection, but is the presence of said convection sufficient for plate tectonics? The answer is no, otherwise plate tectonics would be present on Mars and Venus and not only on Earth. The geodynamic community recognized that another necessary condition for plate tectonics is low strength at plate boundaries and particularly along the plate interfaces in subduction zones (e.g. Zhong and Gurnis 1992, Tackley 1998, Moresi and Solomatov 1998, and Bercovici 2003). To quantify the required strength at subduction interfaces, we have used global models of plate tectonics (Fig. 1A) that combine a finite element numerical technique employing visco-elasto-plastic rheology to model deformation in the upper 300 km of the Earth (Popov and Sobolev 2008) with a spectral code to model convection in the deeper mantle (Steinberger and Calderwood 2006). The model reproduces well present-day plate velocities if the effective friction at convergent plate boundaries is about 0.03 (Fig.1B). Low strength corresponds to subduction interfaces that are well lubricated by continental sediments (low friction; Lamb and Davis 2003, Sobolev and Babeyko 2005, or low viscosity; Behr and Becker 2018). In case of sediment shortages in the trenches (corresponding to a friction coefficient of 0.07-0.1), plate velocities would first decrease about two times (Fig. 1C) and then even more because of less negatively buoyant material having subducted into the mantle, leading to less convection driving force.

Effects of sediments on contemporary subduction according to global numerical models.

Figure 1. Global numerical model showing the effect of sediments on contemporary subduction. (A) The global model combines two computational domains coupled through continuity of velocities and tractions at 300 km depth. (B) NUVEL 1A plate velocities in a no-net-rotation reference frame (black arrows) versus computed velocities (blue arrows) for the global model with a friction of 0.03 at convergent plate boundaries. (C) Root mean square of computed plate velocities in the global model versus friction coefficient at convergent plate boundaries.

Hypothesis and its testing

Based on the previous discussion, we infer that continental sediments in subduction channels act as a lubricant for subduction. In addition, the presence of these sediments in trenches is a necessary condition for the stable operation of plate tectonics, particularly earlier in Earth’s evolution when the mantle was warmer and slabs were relatively weak. With this hypothesis we challenge the popular view that secular cooling of the Earth was the only major control on the evolution of plate tectonics on Earth since about 3 Ga. The hypothesis predicts that periods of stable plate tectonics should follow widespread surface erosion events, whereas times of diminished surface erosion should be associated with reduced subduction and possibly intermittent plate tectonics.

We test this prediction using geological proxies believed to identify plate tectonics activity (supercontinental cycles) and geochemical proxies that trace the influence of the continental crust on the composition of seawater (Sr isotopes in ocean sediments; Shields 2007) and continental sediments in the source of subduction-related magmas (oxygen and Hf isotopes in zircons; Cawood et al. 2013, Spencer et al. 2017). All three geochemical markers indeed show that just before or in the beginning of supercontinental cycles the influence of sediments is increasing, while it decreases before periods of diminished plate tectonic activity, like the boring billion period between 1.7 and 0.7 Ga (Cawood and Hawkesworth 2014; Fig. 2). The largest surface erosion and subduction lubrication events were likely associated with the global glaciation evens identified in the beginning (2.5-2.2 Ga) and at the end (0.7-0.6 Ga) of the Proterozoic Era (Hoffman and Schrag 2002). The latter snowball Earth glaciation event terminated the boring billion period and kick-started the modern phase of active plate tectonics.

Another prediction of our hypothesis is that in order to start plate tectonics, continents had to rise above sea level and provide sediments to the oceans. This prediction is again consistent with observations: there are many arguments for the beginning of plate tectonics between 3 and 2.5 Ga (see the review of Condie 2018) and, at the same time, this period is most likely when the continents rose above sea level (Korenaga et al. 2017).

Cartoon summarizing the factors that control the emergence and evolution of plate tectonics on Earth.

Figure 2. Cartoon summarizing the factors that control the emergence and evolution of plate tectonics on Earth. Enhanced surface erosion due to the rise of the continents and major glaciations stabilized subduction and plate tectonics for some periods after 3 Ga and particularly after 0.7 Ga after the cooling of the mantle. Blue boxes mark major glaciations; transparent green rectangles show the time intervals when all three geochemical proxies consistently indicate increasing sediment influence (major lubrication events); and, a thick black dashed curve separates hypothetical domains of stable and unstable plate tectonics. The reddish domain shows the number of passive margins (Bradley 2008), here used as a proxy for plate tectonic intensity.

What was before plate tectonics?

The earlier geodynamic regime could have involved episodic lid overturn and resurfacing due to retreating large-scale subduction triggered by mantle plumes (Gerya et al. 2015) or meteoritic impacts (O’Neill et al. 2017). Retreating slabs would bring water into the upwelling hot asthenospheric mantle, generating a large volume of magma that formed protocontinents. Extension of the protocontinental crust could have produced nascent subduction channels (Rey et al. 2014) along the edges of the protocontinents lubricated by the sediments. In this way, a global plate tectonics regime could have evolved from a retreating subduction regime.

What is next?

Despite of the support from existing data, more geochemical information is required to conclusively test our hypothesis about the role of sediments in the evolution of plate tectonics. Additionally, this hypothesis must be fully quantified, which in turn will require coupled modeling of mantle convection and plate tectonics, surface processes and climate.

References
Behr, W. M. and Becker, T. W. Sediment control on subduction plate speeds. Earth Planet. Sci. Lett. 502, 166-173 (2018).

Bercovici, D. The generation of plate tectonics from mantle convection. Earth Planet. Sci. Lett. 205, 107–121 (2003).

Bradley, D. C. Passive margins through earth history. Earth Sci. Rev. 91, 1-26 (2008).

Cawood, P. A., Hawkesworth, C. J. and Dhuime, B. The continental record and the generation of continental crust. Geol. Soc. Amer. Bull. 125, 14-32 (2013).

Cawood, P. A. and Hawkesworth, C. J. Earth's middle age. Geology 42, 503-506 (2014).

Condie, K. C. A planet in transition: The onset of plate tectonics on Earth between 3 and 2 Ga? Geosci. Front. 9, 51-60 (2018).

Gerya, T.V. et al. Plate tectonics on the Earth triggered by plume-induced subduction initiation, Nature 527, 221-225 (2015).

Hoffman, P. F. and Schrag, D. P. The snowball Earth hypothesis: testing the limits of global change. Terra Nova 14, 129–155 (2002).

Korenaga, J., Planavsky, N. J. and Evans, D. A. D. Global water cycle and the coevolution of the Earth's interior and surface environment. Phil. Trans. R. Soc. Am. 375, 20150393 (2017).

Lamb, S. and Davis, P. Cenozoic climate change as a possible cause for the rise of the Andes. Nature 425, 792-797 (2003).

Moresi, L. and Solomatov, V. Mantle convection with a brittle lithosphere: Thoughts on the global tectonic style of the Earth and Venus. Geophys. J. Int. 133, 669-682 (1998).

O’Neill, C. et al. Impact-driven subduction on the Hadean Earth. Nature Geosci. 10, 793-797 (2017).

Popov, A.A. and Sobolev, S. V. SLIM3D: A tool for three-dimensional thermo mechanical modeling of lithospheric deformation with elasto-visco-plastic rheology, Phys. Earth Planet. Inter. 171, 55-75 (2008).

Rey, P. F., Coltice, N. and Flament, N. Spreading continents kick-started plate tectonics. Nature 513, 405–408 (2014).

Shields, G. A. A normalised seawater strontium isotope curve: possible implications for Neoproterozoic-Cambrian weathering rates and the further oxygenation of the Earth. eEarth 2, 35-42 (2007).

Sobolev, S. V. and Babeyko, A. Y. What drives orogeny in the Andes? Geology 33, 617-620 (2005).

Spencer, C. J., Roberts, N. M. W. and Santosh, M. Growth, destruction, and preservation of Earth's continental crust. Earth. Sci. Rev. 172, 87-106 (2017).

Steinberger, B. and Calderwood, A. Models of large-scale viscous flow in the Earth’s mantle with constraints from mineral physics and surface observations. Geophys. J. Intern., 167 1461–1481 (2006).

Tackley, P. J. Self-consistent generation of tectonic plates in three-dimensional mantle convection. Earth Planet. Sci. Lett. 157, 9-22, (1998).

Zhong, S. and Gurnis, M. Viscous flow model of a subduction zone with a faulted lithosphere: long and short wavelength topography, gravity and geoid. Geophys. Res. Lett. 19, 1891–1894 (1992).