SALTGIANT Short Course 3 – Numerical and analogue modelling in the Earth Sciences

Author: Ronja Ebner (Utrecht University, Netherlands)

This short course will give all ESRs an insight into the philosophy, methods, and applications of numerical and analogue modelling in the Earth Sciences.

Two months after having spent 10 days in the sunny South at the Mediterranean Sea to learn about seismological signals, we meet again a colder and wetter part of Europe to learn about a different method used in this project. The third ShortCourse dealt with numerical, analytical and analogue modelling and was held in the beautiful city of Utrecht, The Netherlands.

The course started with an introduction to the basics of programming using some matchboxes, MATLAB and the thought model of a desiccated Mediterranean Basin. After two hours we not only had figured out what kind of data and which laws of physics we need to calculate the resulting basin depth, but we also had implemented an algorithm to show the development of a drawdown over time. Those first results were immediately rewarded by lunch and a visit in the Earth-Simulation-Lab. There we not only learned why analogue modelling and cooking are closely related (hint: its not because some of the intersected models look like spekkoek) but we also started a new experiment on Halokinesis. Ok to be honest, we watched, while Jeroen Smit covered the silicon layer with silica grains, but we concentrated hard while doing so. The aim of this experiment was to visualize salt flow and the creation of diapirs and a graben.

After this excurse into analogue modelling and the geology of the Netherlands (the Zechstein Layer consists of 5 evaporitic cycles and has developed graben and diapirs), we resumed modelling with computers. Now Paul Meijer took over and gave a simple and understandable introduction to the theory behind a 1-box model for the Mediterranean and how the exchange with the Atlantic can be implemented for this.

The following days were not less informative and educational. Hanneke Haida and Paul Meyer introduced us to the concept of back-stripping to reconstruct paleo-bathymetries by taking the buoyancy of the lithosphere into account. This knowledge was then used to do some back-stripping reconstruction on our own. Another process, that has influence on the bathymetry is of course erosion. Using the example of the strait of Gibraltar Hanneke Heida introduced us to a simplified version of the model that was used by in Garcia-Castellanos, D. & Villaseñor, A. (2011). At this point we turned to another program to calculate and print results. The model was already preimplemented in Excel and hence we had time to experiment with its parameter space to get a feeling for its limitations and changes in behaviour. Hector Marin Moreno used the same software, but a different approach. He first taught us about the complex nature of liquids under overpressure and then showed us, that we can do the calculations by ourselves by using a excel dataset derived from a real core. This then led us to the first colour-plots of the course. Using a more complex, predefined matlab script we explored the influence of numerical methods on the results. We compared the outcome for different types of boundary conditions and parameter ranges. This helped to understand, that the numerical processes must be treated with the same care as the physical processes and always have to fit the system one wants to model.

The next block, taught by Giovanni Aloisi, used Mathematica and a analytical approach. We thus did not have a look at the evolution of a system over time, but at the steady state for given conditions. Here, we resorted to the 1-box model, that was introduced at day one. This time we focussed on the chemistry of the water and how a change in the mixture of Atlantic ant river waters could influence precipitation of evaporites.

Although the aim of this course was to learn more about modelling and this aim clearly was met, the highlight of the course were the presentations of two former members of the MedSalt project. Walter Capella and Dirk Simon, who both were based in Utrecht during their PhD, gave us valuable insight into how they felt during that time. We learnt how we can make collaboration work and that criticism can be a vital part of science.

Utrecht has even more to offer than just knowledge. The culinary evening programme almost ended every discussion about which country has the best food to offer. A glamorous dinner in one of the old werfkelders was followed by a variety of the best fried potato sticks we had all week, almost drowning in source. To finish the Dutch experience, the last dinner of this workshop was an indinesian rijsttafel that left no one hungry and the discussions ongoing till late at night.

I want to thank Paul Meijer for organising this workshop and everybody else for making it a great week.

List of people who held a workshop, alphabetical:

  • Giovanni Aloisi, PI of ESR6
  • Ronja Ebner, ESR 7
  • Hanneke Heida, ESR 2
  • Hector Marin Moreno, PI of ESR 12
  • Paul Meijer, PI of ESR 7

List of invited speakers:

  • Dirk Simon, Godwin (Laboratory for Paleoclimate Research, University Cambridge).
  • Walter Capella (Postdoctoral Researcher at Royal Holloway, University of London).

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