A method of modeling a salt history for a geologic region containing a salt formation includes defining initial geometry of salt volume and sediment volume in three dimensions, changing geometry of the salt top and maintain the geometries of a top of the sediment and a base of the salt formation for a plurality of time steps, and for each change of geometry, conserving a volume of salt and a volume of sediment. The method includes initially constraining a geometry of the base of the salt during the changing geometry of the salt and sediment volumes, modeling geological activity in the geologic region and modifying the base of the salt formation during a time of the time steps, and modifying the volumes in accordance with the modeled geological activity.