GD
Geodynamics

Geodynamics

The Sassy Scientist – Jekyll and Hyde

The Sassy Scientist – Jekyll and Hyde

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.

Senna asks:


I’m torn between mantle dynamics and lithosphere dynamics as a research topic. Which shall I choose?


Dear Senna,

Could you follow my little Jekyll and Hyde routine over the past two posts, railing about lithosphere dynamics and mantle convection? Some people did not, as my inbox will testify. This is basically what it has been over the past few decades. Let’s be clear: we don’t live in the 70’s anymore. We’re capable of more subtlety and have to live in the in-between: the world is full of grey tones (yes, also shades of grey).

Numerical modelling of mantle convection systems that includes oceanic and continental lithosphere has greatly improved. Producing tessellation of the Earth’s surface and long-term supercontinent cycles in combination with realistic surface kinematics is a big step forward. Does this mean we completely understand the solid Earth system? Definitely not. Do mantle convection modellers have to realise that the relative importance of the mantle on surface kinematics may only be a transient feature on a regional scale, and that surface motions may be unrelated to mantle flow? Maybe. Do lithosphere dynamics modellers have to realise that the relative importance of the mantle on surface kinematics may only be a transient feature on a regional scale, and that this doesn’t mean that the mantle definitely always or never influences surface motion? Maybe. Does everybody involved need to realise that their idea of the truth may not be the whole truth? Definitely. Is there a place for both lines of inquiry into understanding the solid Earth system? Undoubtedly.

I’ll come back to your question. There is no mutual exclusivity between mantle convection and lithosphere dynamics. It’s all part of the same system. So whatever you choose, just realise this: do not blindly step into the mantle convection gateway or lithosphere dynamics portal to the maze of solid Earth dynamics and kinematics. Both alleyways will probably end up in the same central square of enlightenment.

Yours truly,

The Sassy Scientist

PS: This post was written after getting hammered repeatedly by the Editor-in-Chief over my previous two posts.

Let’s talk about plagiarism

Let’s talk about plagiarism

Hey you! Do you have 5 minutes to talk about plagiarism?
Have you ever wondered if some parts of a thesis that you have supervised are simply a copy-paste from another thesis or article? This week, an anonymous guest author will tell us about their personal experience with plagiarism in science and what can be done against it.

Granted, it is not the most fascinating topic. Until recently, I really thought there was nothing to say about it. Everybody agrees that plagiarism is bad, and one shouldn’t do it, right? Plagiarism is just for a pair of lazy bachelor students or maybe one or two entitled old professors who believe they are untouchable, right? Right?! Oh boy, was I naive!

For me, it all started with reading a few words that do ring a bell on a master student thesis that I had co-supervised. After some more investigation, I realized that this student did indeed copy and paste sentences and even paragraphs from my PhD thesis, as well as from other articles. He did also plagiarize in former assignments and in a scientific article he published in a journal at the beginning of the year. Uh uh.  At this point, the student had already defended his thesis and just got his master degree validated. In the process, the thesis had been evaluated by two independent reviewers and also had been read by my two PhD advisors. Nobody suspected anything. And this happened at THE top Earth science research institution of a country which is renowned for the quality of its research. No problem, I think, I contact the co-supervisor and the director of studies. For sure they’ll know what to do. Hahaha. I spare you the details, but, to sum it up, the master degree had already been awarded, so there was no way whatsoever to change anything about it.

I didn’t make friends this past few weeks by insisting and playing the self-righteous scientist card. The student still got his master and will soon be enrolled in the PhD program of the same institution. However, my complaining seems to have had some effect. In the institution in question, they will buy the rights to a plagiarism scanner software and create a special commission to deal with plagiarism cases. From now on, master students will have to include a declaration of originality for their master theses, and they will have a course on research integrity. If the same situation arises, there will be official tools to deal with it, and hopefully the education the students will receive will help prevent plagiarism.

So yes, sometimes it’s worth it to be (a bit) annoying. Here are a few other things you might want to consider in order to avoid this kind of situation.

Plagiarism and “self-plagiarism” (also called text recycling) are not allowed by most journals, however, there is quite a large part of the scientific community that does not see the problem with self-plagiarism and does it regularly in articles. Some copy whole paragraphs from former articles of theirs and, sometimes, these articles pass the plagiarism scan that journals generally do. So it is really worth it to scan for plagiarism every paper you receive to review. That’s how I gave my fastest peer review ever: 5 minutes to scan the article, 5 min to realize that a whole section was a copy and paste from another article, and 5 min to write a rejection message.

Check every thesis, every draft and every paper you receive with a plagiarism software. You might have some surprises. If you do so, you’re making students/co-authors a favour. Had I done that check with my student prior to his thesis submission, he could have had the chance to make things right, avoided cheating on an exam, and got his master degree fair and square. Instead of this, he has to walk around with a master diploma he didn’t really earn. Not a good start in one’s professional life. Same with co-authors:  if you catch their plagiarism, you save all your team the embarrassment of getting your paper rejected by a journal because of this.

It might be a good idea to check the policy of your institution on plagiarism before you’re faced with the situation I described earlier. If there is nothing planned, urge people in charge to set up some procedure. You don’t want to be in the situation of catching a student after his master has been validated and not being able to do anything about it.

Finally, to people who practice text recycling: if you want to copy a sentence from another article because it is the best sentence to describe your thoughts… Why not putting quotes? If you don’t, you’re just being dishonest.

 

The Sassy Scientist – Hyde: Lithosphere Dynamics

The Sassy Scientist – Hyde: Lithosphere Dynamics

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.

Senna asks:


I’m torn between mantle dynamics and lithosphere dynamics as a research topic. Which shall I choose?


Dear Senna,

I don’t know what came over me when writing last week’s post. Must have been something I ate. Sometimes I just get some crazy idea stuck in my head. For example, I completely misconstrued ideas on the relative importance of mantle convection over lithosphere dynamics.

Last week I was babbling on about plate tectonics, and how the focus on the lithosphere shifted attention away from mantle convection. To be clear: this was for good reason. Granted, McKenzie and Parker’s (1969) concept of rigid plates on a shell was simplified. That was also the point: it explains some first-order observations like relative plate motions and seismicity. No, plate boundaries are not necessarily narrow zones of deformation (Kreemer et al. 2014). Yes, plates can also be flexed through loads on top, or radial mantle tractions from below (Watts 2001). We know that the Earth’s lithosphere can generally be considered to be a visco-elastic plate that is primarily moved by forces acting at its boundaries. Does this preclude seismicity or deviations from principal stress directions far away from such plate boundaries? Of course not.

It is obviously a great idea to base model predictions on non-unique gravity and geoid observations, seismic tomography, and Earth’s normal mode undulations for structures 2500 km away from the surface. The surface. You know, that place where we actually have direct observations. Sure, just extrapolate some rheology measured on a rock sample down to the lower mantle using some equations of state. Should be similar, right? Do you have a kinematic plate tectonic reconstruction based on loads of geological and paleomagnetic data? Just pop it into a mantle convection model to see whether it is feasible. You measured some SKS splitting data? That’s definitely a measure of present-day mantle flow. You infer instantaneous dynamic topography at the surface in the order of a couple 100 meters? Mantle convection models predict kilometers of instantaneous dynamic topography, so you must have made a mistake in your observations.

Do you want to understand what’s driving deformation of the lithosphere? Choose lithosphere as a research topic. Do you believe in fairy tales? Look into mantle convection: it’s full of magic.

Yours truly,

The Sassy Scientist

PS: This post was written after recovering from a major headache from reading last week’s post.

PS2: I won’t be surprised if there is going to another post on this topic next week. How well do you know your Scottish literature?

References:
Kreemer, C., G. Blewitt, E.C. Klein (2014). A geodetic plate motion and Global Strain Rate Model, Geochemistry, Geophysics, Geosystems, 15, 3849-3889, doi:10.1002/2014GC005407
McKenzie, D., and R. L. Parker (1967), The North Pacific: An example of tectonics on a sphere, Nature, 216, 1276
Watts, A. B. (2001), Isostasy and flexure of the lithosphere, Cambridge University Press, 458 pp.

Iron volcanism on metallic asteroids?

Metallic asteroid

This week, Francis Nimmo, professor in the Department of Earth and Planetary Sciences (University of California Santa Cruz), tells us about volcanism on metallic asteroids! Around and after the formation of the solar system (4.5 billion years ago onwards), volcanoes on some of the gigantic bodies of the asteroid belt might have erupted … iron. Explanations.

Francis Nimmo

Francis Nimmo

One way in which we can learn about the insides of planetary bodies is by looking for signs of volcanism. Volcanism transports molten material from the interior to the surface of a body, where it solidifies. Something similar may happen on icy bodies, where cryovolcanism is thought to occur. Together with Coby Abrahams, one of my grad students, I recently wrote a paper proposing “ferrovolcanism”, which is the eruption of metallic iron. We suggested that this may have happened in the past on metallic asteroids.

 

What are metallic asteroids? Some asteroids, such as 16 Psyche are thought to be made mainly of iron and nickel, on the basis of their spectra and radar signatures. They probably originated from a catastrophic collision. The picture is that a proto-planet, which had already formed a dense metallic core, was broken apart so violently that its core was fragmented, and the fragments then cooled to form free-floating metallic bodies. Such an event would also explain the large number of iron meteorites in our collections. So far we have never seen a metallic asteroid up close, but NASA is planning to send an orbiter which will reach 16 Psyche in 2026.

Iron meteorite

Artistic view of an iron meteorite with ferrovolcanism (Elena Hartley)

How would “ferrovolcanism” work? Immediately before the catastrophic collision, the core would have been liquid (because the silicate mantle is a good insulator). After the collision, the surface of a free-floating iron blob would have initially cooled very rapidly. Analysis of iron meteorites tells us that, in some cases, the blob developed a strong, cold iron crust. The melt (liquid iron) beneath the crust would have been less dense than the crust – just like molten magma on Earth. And so, just like magma on Earth, the liquid iron would tend to rise to the surface – hence ferrovolcanism.

There are a few factors that make ferrovolcanism less likely than silicate volcanism. One is that, as the iron crust cools, it contracts, putting the whole body into compression and making it more difficult for melt-filled fractures to open up. Another is that iron is both ductile and strong, so that fracture propagation is harder. And iron is also much more thermally conductive than rock, so that melt-filled fractures will cool and solidify rapidly. Nonetheless, we don’t think any of these factors is fatal. For instance, Mercury also experiences global compression but still shows signs of volcanism. Iron eruptions might be aided by volatiles coming out of solution, just as with terrestrial eruptions, although the catastrophic impact may have removed some volatiles.

How do we test this hypothesis? One way is to wait for images of 16 Psyche! If we see things that look like iron volcanoes, that would be interesting. But identifying signs of ancient volcanism is notoriously hard – this paper documents several proposed volcanic or cryovolcanic features which turned out to be something else on further investigation. And our calculations show that the volume of erupted material will be only about 0.1 percent of the total volume of Psyche, so these features may be hard to spot – especially after 4 billion years of erosion by impacts.

Another way is to look at the iron meteorites in our collections, because ferrovolcanism should produce anomalous-looking meteorites. For instance, one might find vesicle-rich samples, or ones happening late in the crystallization sequence but showing extremely rapid cooling (because they were erupted to the surface).

How did we write the paper? It was more or less accidental. Coby was working on how iron asteroids might lose their volatiles early when one day he turned to me and said “I think they’ll erupt!”. I thought this was a neat idea, and so we started to look at how the eruptive process might work.

The strangest part of writing our paper was that at the LPSC conference someone came up to me and said “I just invented iron volcanism!”. It turned out that another group had been working on ferrovolcanism completely independently. They suggested that pallasite meteorites might be evidence of ferrovolcanism (something that I had completely missed). This simultaneous but independent development of ideas seems to be quite common in the Earth Sciences – but that is a topic for another day.