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Geodynamics

nethermod 2017

NetherMod Day 3 – Secret Summary

NetherMod Day 3 – Secret Summary

The third day of NetherMod promised to be a great day full of science, until it turned into a great day full of fun activities, such as windsurfing, wine tasting, and karaoke, thanks to the Dutch weather. This meant that only the morning was filled with science, which has already been summarised expertly in our previous post.

What then, can this post add, I hear you thinking..? Well, let’s start with saying that the cooking theme is still going strong here on NetherMod 2017: John Herlund discussed the BEAMS (bridgmanite enriched ancient mantle structures) hypothesis from Ballmer et al., 2017 and ended up referring to the bridgmanite blobs as ~10,000 km sausages during the student discussion. Just let that sink in for a moment… So, now in addition to the delicious potatoes we discussed earlier, we have a nice plate of sausages. We still have two days to go, so maybe we will have a full (Dutch?) meal by the end of the conference. Who knows?

Besides that, we can report a scoop from one of our very anonymous reporters (Laetitia Le Pourhiet): the reason Wim Spakman did not attend the Monday morning talks on rifting processes was not because he was sick, but actually because he was ‘sick’ of rifting processes, as he is a subduction man through and through! However, no definite proof has been provided so far, so be aware that this might be fake news.

To conclude, your faithful NetherMod reporter has gathered for you the most memorable quotes of the day by René de Borst during his keynote lecture on plasticity and fracture in porous media. He stated that one of the most obvious solutions for dealing with the mesh dependence problem is to just accept it (I mean, he has got a point) and he noted that the devil is in the boundary conditions. However, his most beautiful quote related to the concept of continuity:

The world is neither continuous nor discontinuous. The perception of continuity or discontinuity depends on the level of observation.

With that inspirational quote in mind, I hope you are ready for yet another science day!

PS: Of course, we can’t forget Thorsten Becker’s excellent talk on subduction dynamics, but he didn’t make any obvious food references, so how am I supposed to include his talk in these secret summaries?
PPS: Martin Ruess is online

NetherMod Day 3 – Karaoke fun!

NetherMod Day 3 – Karaoke fun!

Reporting live from the NetherMod karaoke bar, Manar Alsaif, PhD student at Université Montpellier, part of the Subitop ITN, summarises her experience with geodynamical karaoke (also see this post on the relationship between the two).

Day 3 of NetherMod sizzled in a high of 29 °C, which meant the free afternoon just had to be that day. Of course, the day of the free afternoon had to round up with wine tasting and karaoke after dinner. How convenient that the wine tasting preceded the karaoke, because karaoke needs quite a bit of lubrication! It started off with a few brave, surprisingly sober souls chiming their way through the Beatles and the Eagles and the like. As more wine poured into the glasses, more people poured into the karaoke room. A group danced their way through the YMCA, everyone managed to join into a Japanese tune (TRAIN TRAIN!), and even some Nirvana found a couple of grungy throats. The range was impressive, not least some of the gentlemen’s soprano worthy falsettos. All in all, an excellent break well earned after an intensely informative day and a half.

NetherMod Day 3 – Science & Windsurfing

NetherMod Day 3 – Science & Windsurfing

Let’s keep going with the programme: today’s talks dealt with the following topics:

(1) Lower mantle rheology–what do we really know?

(2) Modelling plasticity and fractures in porous media: everything goes wrong!

(3) Complexities of subduction dynamics.

The first keynote talk was on the rheology of the lower mantle, an important part of the Earth. John Hernlund spent his 45 min describing what the lower mantle is and what it is made of. He also went over where you can find surface expressions and its importance in shaping our planet.

How can we possibly know what’s in the lower mantle if it is so far below the surface? 

Geodynamic modellers have to get creative to figure out what the lower mantle is made of.

Although uncertainties of present data preclude precise numerical predictions, several interesting achievements in this area have recently been published. So, stay tuned!

The second talk–by René de Borst–was about the mechanical behaviour of geomaterials. He gave an overview of how complex these materials are, from almost the onset of loading to shear deformation and the volumetric response. Modellers have been warned about the possibility that non-uniqueness occurs as a consequence of strain softening and plasticity. Since different options exist, we should keep discussing the physical consequences carefully!

Thorsten Becker had the last talk of the day. What did we learn from him? Very briefly, we can summarise it in three key-points:

(1) Rock rheology is a usual suspect for uncertainty;

(2) Oceanic slabs reign supreme in controlling plate motions;

(3) Two slabs are better than one!

Free afternoon – Introduction to windsurfing 

This afternoon the NetherMod crew had the chance to stop talking about slabs, rifting, plasticity, and partial differential equations. One group went to the lake for an awesome windsurfing lesson.

Why is windsurfing awesome?

After this unforgettable experience, geodynamic modellers have heaps of reasons why they would say that windsurfing is the best sport ever. All you have to do is ask any modeller “Why windsurfing?” and they will give you explanations of what makes windsurfing great.

A young geodynamic modeller ready for windsurfing!

 

Windsurfing is easy

There are tons of sports that are hard to learn: bike riding, snowboarding, rock climbing and the list goes on. Windsurfing has a great advantage in that you can make the learning environment ideal, even if you are a nerdy scientist! You only need flat water and light constant winds.

Windsurfing is a great exercise

Obviously all sports end up being good for fitness. However, the great thing of windsurfing is that the intensity varies along with your level, in the same way as you work on numerical codes!

So, do you believe it? Two more geodynamicists try to convince you:

Simon Preuss (PhD student, ETH Zürich, Switzerland):

“Wow, what a great day. I mean, usually I don’t do sports and every sport I start gets boring really quickly.
But you know… I got the feeling windsurfing is different: it’s a sport that you do alone on your own board with your own sail–sounds depressing, I know. But actually we went with a group of 20 people and everybody managed to catch the wind right away. And well, I guess after ~1 hour we were ~20 meters away from the coastline–it was great!!
If I had the chance to do it again I would do it right away. It’s just surprising how fast you can learn sports. Definitely easier then understanding geodynamic models.”

Anna Gülcher (MSc student, ETH Zürich, The Netherlands and windsurfing teacher):

“I must say the geophysicists pleasantly surprised me in how fast they picked up the windsurfing. Within half an hour everyone stood up straight and was actually windsurfing. It’s a pity the wind was not strong enough to fully challenge everyone!”

Very happy geodynamicists after their windsurfing experience

 

NetherMod Day 2 – Secret Summary

NetherMod Day 2 – Secret Summary

The first science day at Nethermod was kicked of by the crust & lithosphere modelling session, followed by the first talk in the methodological advances session. Thibault Duretz discussed how using lithospheric heterogeneities can help to form complex rifting styles without using an explicit strain weakening formulation. Switching to the subduction evolution of the Farallon plate, Claire Currie next discussed potential mechanisms to form a flat slab (or at least decrease the dip of the slab) and later remove it. She also reminded us of a truth that we’d better keep in mind for the rest of the conference:

All models are wrong, but some are useful

by the late George Box, a British statistician. Switching again to rifting processes (what a wonderful program!) Sascha Brune discussed how rifting processes can be potentially important in the global shallow carbon cycle. The last talk was given by Dave May, who talked about computational methods for two phase flow. Although a very interesting talk, Dave really got everyone excited when he showed table after table completely filled with the number 2.0, which was apparently optimal.

The discussion in the afternoon focussed on the problem of how to start your model, which was initiated (get it?) by Susanne Buiter. In the end, the main consensus seemed to be that there are two possible methods, mainly summarised by Casper Pranger: either you have a generic model for which you should determine the influence of different initial weak seeds to check how robust your model is, or you have a region-specific model for which you find the optimal initial conditions to get your desired model output. Of course, as Carolina Lithgow-Bertelloni noted, you will never know the exact initial conditions or present state of a region, so both input and output will always be inherently flawed (also see the previously mentioned quote by George Box).

Apart from this interesting discussion, we also learned what the main etiquette during a Geodynamics dinner party would be: never ever offer Laetitia Le Pourhiet potatoes, because she does not like them, although she might’ve liked them in the past. Thibault Duretz on the other hand, will feast on the potatoes and really can’t get enough of them. Although, to be fair, I’m not sure exactly what kind of potatoes he likes. Usually whenever I cook potatoes, they are not red, perfectly elliptical, on the km-scale size and/or stuck inside the lithosphere. Oh well. Each to their own.