1. A method of generating a horizon surface based on multiple candidate horizon surfaces, the method comprising: selecting seeds that represent different starting locations within a desired horizon surface; generating a plurality of candidate horizons from the selected seeds; generating the horizon surface by combining, for each point on the horizon surface, depth values from corresponding points on the plurality of candidate horizons into a single representative depth value; computing an uncertainty for each point on the horizon surface based on a difference between two or more depth values from the plurality of candidate horizons that create the single representative depth value, respectively; and creating a model of the subsurface region using the horizon surface.