Lukas models salt tectonics

2016-05-13

The salt diapir in the Zagros mountains. Photo: Hemin Koyi.

One of the big challenges in the geosciences is how to study the slow geological processes that take thousands or even millions of years. In other words, how can we possibly understand deep time, firmly rooted in our short human perspective on time? 

The classic method for studying deep time in geology is to observe similar geological formations at different stages of their evolution, in different places on the planet. Then, it's matter of piecing together the geological processes and the evolution over time, a bit like assembling a motion picture from short film sequences scattered all over the planet! Another method is to construct numerical models that simulate geological processes over millions of years under controlled and variable conditions. This is the method doctor Lukas Fuchs employed in his PhD thesis, that was successfully defended earlier this month.

- By using our numerical models where each individual particle has defined thermodynamic and physical properties, we can model how each particle would behave under deformation, Lukas explains. The point of all of this is to explain how existing salt diapirs have formed, and perhaps more importantly, how they will behave in the future. 

An example of Lukas' modelling of salt tectonics. 

Why is understanding salt tectonics important? 

- Salt deposits behave very differently from other geological units, such as sandstone and limestone, Lukas says. While a sandstone deforms in a brittle way in the upper crust, salt deforms plastically. So, when you deform e.g. a sandstone together with salt, it is like you are squeezing bee's wax mixed together with bricks! This, in turn, leads to interesting salt tectonics and formations. 

The plastic deformation of salt also means that it is more resistant to destructive events such as earthquakes. For that reason, several countries are interested in storing their nuclear waste inside salt diapirs, thinking that they will be safe in the case of a major earthquake in the future. The most famous such example is the Gorleben salt diapir in Germany, that is already used for this purpose.  

- Salt does definately provide a good protection against for example earthquakes, but this doesn't necessarily mean that it is wise to store nuclear waste inside them for thousands of years, Lukas tells me. By modelling salt deformation in deep time, we improve our understanding of salt tectonics and our ability to predict whether salt diapirs such as Gorleben can be good sites for storing our nuclear waste in the long term.  

If you want to read more about Lukas' research, you can download the thesis on this link. Besides salt tectonics, his research also includes studies of deformation in the upper mantle, beneath the oceanic crust.  

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