numerical modelling

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.

NetherMod Day 2 – The science starts

NetherMod Day 2 – The science starts

Yue Zhao

Today’s NetherMod update is written by Yue Zhao. She did her MSc at Utrecht University and is now a PhD at Vrije Universiteit Amsterdam. To study the thermal evolution of the Moon, she incorporates high temperature and pressure experimental results from her group into numerical models of lunar mantle convection.


After a wonderful ice-breaking evening in the glimmering setting sun over Lake Veluwemeer, today we started off the first day of science!

Today’s talks followed the theme of crust/lithosphere modelling. The topics ranged widely from the rifting of mechanically heterogeneous lithosphere to the generation and destruction of flat slabs, from continental rifting modelled at a global scale to renewed computational methods for two-phase flow. Even though these are not exactly the topics I focus on in my PhD, it was great fun to hear about what other cool work my fellow geodynamicists are doing.

What I really like about this conference is that the talks are one hour long, so the speakers really have the time to provide the background and build up their stories. Unlike the common ten-minute presentations at most other conferences, which are only meant for people who are already familiar with the topic, the long talks at NetherMod are meant to properly introduce problems and invite discussions. They are meant for everyone in the room to understand!

What is the future of geodynamics? It is in the advances of mathematical and physical understandings of natural processes, in better software, in more realistic parameters, in more accurate observations with which we can evaluate our models. The future of geodynamics is what WE create. So, stay tuned to this community!

NetherMod Day 1 – Breaking the ice

NetherMod Day 1 – Breaking the ice

This week the EGU Blog Team is attending Nethermod, so we will give you daily updates! Nethermod is the XV International Workshop on Numerical Modelling of Mantle and Lithosphere Dynamics. The 2017 workshop is held at a lakeside hotel near Putten, The Netherlands. The meeting is co-sponsored by the Utrecht University, the Oslo University Centre for Earth Evolution and Dynamics (CEED), the European Geological Union (EGU), and the Computational Infrastructure for Geodynamics (CIG).