Dear all,
I am writing because I am trying to run a model where the lithosphere is simultaneously subjected to extension and plume impingement. In my intention, when the plumes reach the LAB, I should start the lithospheric extension and produce fast delamination.
However, I have noticed that, as soon as the extension starts, my model does not converge anymore, regardless of the solver I use for my simulation. In addition, the residual is often very large (sometimes higher than 10^18).
Here I enclose one of my input files (actually one of the most successful ones, where the residual is “only” 260). In this model, I apply extension on the sides of the lithosphere, whereas the remaining parts of the lateral boundaries are open.
original.prm (18.2 KB)
Any help would be very appreciated. Thank you very much! 
Alessio
Dear Alessio,
Thanks for posting to the forum! Indeed, a residual of 260-10^18 is too high as you have noted 
In addition to the PRM file, what would would also help to diagnose the issue is the following:
- The log.txt file that accompanies the PRM file
- Images from the model run that illiustrate the dynamics and any potential issues/features leading to the poor convergence behavior
- A history of how you developed the PRM file and at what stage things stopped “working”. For example, you note that currently the solvers break when you apply extension on the boundaries. Was there a previously model that did show good convergence when you applied extensional BC?
Cheers,
John
Dear John,
thank you very much for your quick answer and for your help. Here I attach the log.txt file and a few images of one simulation, the time step before it stops converging.
Regarding the development history of the model, previous versions had a thickness of 400 km, activation volumes for mantle materials between 18e-6 and 25e-6 J/Pa, and lower densities for the lithosphere and the mantle (around 3300 kg/m3). I realized that the model stopped converging when I decreased the activation volumes and increased the density of both the lithosphere and the mantle.
Right now I am trying to run a successful model by changing each parameter one at a time, and then I will try to combine more parameters simultaneously, in order to understand what does not work.
Another aspect to mention, the lateral boundaries were not open in my previous simulations, but I implemented a box geometry with a lateral outflow to keep the volume of the model constant. In any case, when I re-apply my old boundary condition I still do not obtain convergence.
Once again, thanks for everything.
Best,
Alessio
log.txt (5.5 MB)