| 24 Mar 2026
LaScape 1.0: An open-source module for three-dimensional thermo-mechanical and landscape evolution modeling
Abstract. The feedback between tectonic events and surface processes fundamentally shapes landscapes and lithospheric deformation. However, the quantitative interaction remains poorly constrained. While numerical simulations offer powerful insights, 3D numerical models that couple thermo-mechanical processes with landscape processes remain uncommon due to the mismatches in temporal and spatial scales. Here, we present a 3D coupling methodology that integrates the thermo-mechanical code LaMEM with the landscape evolution code FastScape. A finite-difference marker-in-cell technique solves the thermo-mechanical processes, and a sticky air layer at the top boundary, combined with an internal mesh, effectively and stably simulates the free surface. Each timestep is synchronized with a finite-difference landscape evolution model. The timesteps of LaMEM are read by FastScape, which then subdivides them into smaller, iterative intervals to simulate surface processes. We demonstrate that the coupled model operates efficiently and stably. We validate our couple model by applying it to three classical tectonic regimes: oceanic subduction, continental collision, and continental extension. These cases converge quickly and align well with geologically realistic results. This approach provides a powerful, quantitative tool for exploring the bidirectional feedback mechanisms between the deep Earth and its surface, offering insights into the genesis of complex geological structures and landscapes.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Geoscientific Model Development.
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In this paper the authors coupled the geodynamics model LaMEM with the landscape evolution model FastScape. They present in this paper this coupling as a separate code coined LaScape1.0. In the first part of the paper they briefly explain how LaMEM and FastScape work. Then they explain how LaScape1.0 achieves the desired coupling between the two models. Finally the authors show two examples of the coupling, one subduction models, which later goes into continental collision and one continental extension model. The authors claim that their works shows the importance of fully 3D coupled models and that their models show that the impact of surface processes on geodynamic processes is limited to relatively small spatial scales.
Since the article type is a "Model description paper", I will use the description from https://www.geoscientific-model-development.net/about/manuscript_types.html as a guideline.
- "The publication should consist of three parts: the main paper, a user manual, and the source code, ideally supported by some summary outputs from test case simulations."
Besides a small readme in the Zenodo repository, I could not find a user manual. The source code is available in the Zenodo repository. It contains LaMEM, the code for the coupling FastScape to LaMEM, and the input files to run the models shown in the paper. So, besides the missing manual, the submission seems compliant. It is very clear tough that this is an extension of/plugin for LaMEM which allows the use of FastScape, and not a separate code or model.
- "The main paper should describe both the underlying scientific basis and purpose of the model and overview the numerical solutions employed. The scientific goal is reproducibility: ideally, the description should be sufficiently detailed to in principle allow for the re-implementation of the model by others, so all technical details which could substantially affect the numerical output should be described. Any non-peer-reviewed literature on which the publication rests should be either made available on a persistent public archive, with a unique identifier, or uploaded as supplementary information."
The introduction is generally fine, but even though the authors are aware, and used the ASPECT-FastScape coupling, as stated in their Author contributions, they do not include it in the discussion or cite the paper which implemented that coupling (https://doi.org/10.1130/G49351.1), which would seem appropriate for this kind of paper. Especially since they state the fully 3D coupled models are uncommon, with the ASPECT-FastScape coupling being a fully 3D coupling (and 2D). The original paper was actually in 3D, but was only very thin, but it was for example used in https://doi.org/10.55575/tektonika2024.2.2.75 as a real fully 3D coupling.
The paper does a decent job of describing the methods they used to implement the coupling, although I do think there could be more focus on the details of the coupling itself compared to the LaMEM and Fascape descriptions. For example, based on the text and figure 1, it is not clear to me whether all data is send to rank0 and then the surface is filtered out, or only the surface node data is send to rank0. Nor is it explained how the velocity and topography parameters are exchanged without any loss of information (no interpolation in the process at all?). Other information which might be useful to potential users might be how much extra compute time does it cost to have this coupling enabled, and how much of that time is spend in the coupling part, compared to LaMEM and FastScape? In my view the approach for the coupling is straight forward and has been done several times before. So although I am sure this is a nice addition to LaMEM, method wise there is as far as I can see nothing new here. What the paper doesn't discuss well what the limitations and caveats of the coupling are. What kind of models can and can't be run, under what conditions does the solution become inaccurate, etc.
It is not fully clear though what versions of LaMEM and Fascape they used. This should be documented more clearly in the paper. Especially since there are now multiple very different versions of FastScape. I think that they used the Fortran version of FastScape, and not the newer C++ version, but this should be documented well in the paper, which exact version numbers, to make it reproducible.Â
- "The model description should be contextualised appropriately. For example, the inclusion of discussion of the scope of applicability and limitations of the approach adopted is expected."
see point above.
- "Examples of model output should be provided, with evaluation against standard benchmarks, observations, and/or other model output included as appropriate. In this respect, authors are expected to distinguish between verification (checking that the chosen equations are solved correctly) and evaluation (assessing whether the model is a good representation of the real system). ..."
The two codes that have been coupled are standard community codes, and as far as I am aware, there are no standard benchmarks for coupling of these kind of models. Besides that the output seems, in the eyeball norm, alright, there is no verification as defined above. Technically, since the code is available, anyone could check whether the implementation is done correctly, but I don't think that is what is meant with this point.Â
- "Code must be published on a persistent public archive"
The coupling code together with the used version of LaMEM is in a persistent public archive. The user has to obtain PETSC and FastScape by themselves.
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General points:
In my view this is a plugin for LaMEM, which couples it to FastScape, not a separate model. This makes me doubt whether it make it worth it to publish in this journal. There is value to having a detailed description though to how these kind of couplings work, but this paper also seems to lack in that regard.Â
The paper tries to also present some new scientific findings with the coupling ("Model results indicate that the impact of surface processes on geodynamic processes is limited to relatively small spatial scales"), which this is definitely not the type of article for. In my opinion, besides not being the place to make these kind of statements, I do not think these kind of conclusions can be drawn from these kind of simple, low revolution proof of concept models. I would like to see significant more evidence for such claims to be made.
To add to this, the parameter study the authors do seems to be focused on investigating the effects of varying the parameters on the resulting model, not to show that the coupling works well under various types of conditions.
I would like to add that, although I generally agree with their statement that fully 3D couplings can be useful and important ("further demonstrate the advantages of using fully coupled 3D models"), if you would make such a statement, it would be great to actually add a 1 to 1 comparisons between a T-coupled model (2D LaMEM with 2D fastscape) and a fully 3D coupled model to actually compare the differences. Especially since the examples they show are basically laterally extended 2D models, and do not (initially) contain any 3D complexity.
Conclusion:
I will leave it up to the editor whether this manuscript is fitting for this journal, but even if it is, I think it would require major revisions before it can be published.