MOLASSES (MOdular LAva Simulation Software for Earth Science)

MOLASSES is a lava flow simulation tool designed to forecast inundation area by lava flows.

MOLASSES - At a Glance

MOLASSES stands for MOdular LAva Simulation Software for the Earth Sciences. PDF file (20MB) provides some background on the statistical modeling of lava flows. PDF file (10MB) provides some background on on the statistical modeling of volcanic vent locations. The code relies on a cellular automata algorithm to estimate the area inundated by lava flows. Check out this simplified illustration of cellular automata for lava flows. MOLASSES does not model the rate of lava emplacement or the physical dynamics of lava flows. A digital elevation model (DEM) of the volcanic region is pre-loaded on the server; lava flows are simulated using this DEM. Rheology is accounted for by specifying a modal lava thickness. The thickness of lava flows, especially their margins, is a function of the lava flow yield strength. Yield strength is a more useful rheological parameter than viscosity, since the code does not account for physical dynamics.


MOLASSES expects the following inputs:

  • volcanic vent location -- Specify location as an easting and northing in UTM coordinates, or choose a spatial density model to randomly pick a probably vent location based on the distribution of mapped vents comprising the volcanic system. Hint: The first time you run MOLASSES, specify location using spatial density to see the map area in UTM coordinates.
  • lava residual or modal thickness -- Typical values range from 2-meter -- 50-meter thicknesses. The code distributes lava accumulations (lava thickness) from cell to cell. Lava will pool or thicken in low lying areas and will thin at the flow margins. The residual thickness should be consistent with the yield strength of the simulated lava flow.
  • lava flow volume -- Typical values range from 1e6 (1,000,000) cubic meters to 1e10 cubic meters; 1e9 corresponds to one cubic kilometer. MOLASSES continues to execute until this total volume of lava is erupted on to the DEM.
  • lava flow pulse volume -- Typical values range from 1e4 (1000) cubic meters to 1e6 cubic meters. This volume is a fraction of the total lava flow volume, a volume of lava erupted from the vent cell and spread over the topograpy until exhausted. Relatively small pulse volumes tend to make the lava flow closely follow the topography; large pulse volumes allow the lava flow to bury topography by surmounting obstacles, especially near the vent.
  • Digital Elevation Model (DEM) -- MOLASSES can read in any DEM that is readable by gdal routines. Currently, users can only erupt lava flows on DEMs stored in the server DEM library. Should you have a DEM that would be a good addition to our DEM library, please contact Laura Connor or Chuck Connor


MOLASSES produces the following outputs:

  • A map, PNG file (flow0.png), showing the area inundated by the lava flow on a shaded relief DEM -- You can choose to save the PNG image by right-clicking on the map and selecting an appropriate option. Vent location is indicated by a white circle on the map; the flow will be in shades of orange, darker shades indicative of increasing thickness.
  • A text file (flow0) of flow locations in UTM coordinates and lava thickness in meters
    (file format:)
    (first line) easting northing volume pulse residual
    (...) easting northing thickness new_elevation original_elevation

Note the [Choose a file to download] button. You can select any of the input, output, or log files created by the tool and view or download them. The log files are useful if no lava flow appears on the map or no map is produced. An error situation occurs if the vent is selected outside of the map area or if the lava flow reaches the boundary of the map area. Check the log files if either of these situations are suspected.


  • The MOLASSES source code can be downloaded from GitHub
  • Original application of the proto-(perl)version of MOLASSES:
    Connor, L. J., Connor, C. B., Meliksetian, K., & Savov, I. (2012) Probabilistic approach to modeling lava flow inundation: a lava flow hazard assessment for a nuclear facility in Armenia. Journal of Applied Volcanology (1):3. DOI 10.1186/2191-5040-1-3
  • Comparison of MOLASSES output for an actual lava flow:
    Kubanek, J., Richardson, J. A., Charbonnier, S. J., & Connor, L. J. (2015) Lava flow mapping and volume calculations for the 2012–2013 Tolbachik, Kamchatka, fissure eruption using bistatic TanDEM-X InSAR. Bulletin of Volcanology 77(12):106. DOI 10.1007/s00445-015-0989-9
  • Benchmarking MOLASSES and similar codes:
    Dietterich, H. R., Lev, E., Chen, J., Richardson, J. A., & Cashman, K. V. (2017) Benchmarking computational fluid dynamics models of lava flow simulation for hazard assessment, forecasting, and risk management. Journal of Applied Volcanology 6(1):9. DOI 10.1186/s13617-017-0061-x

The development of MOLASSES was partially funded by a grant from the US National Science Foundation.