Geologists create volcanic hazard maps using scientific data to portray potential future geological events; the end users are principally public safety officials. Typical maps use a few simple polygons to outline areas of potential inundation or cover by a few categories of flows based on past frequency and size. Uncertainties in data regarding flow characteristics complicate the construction of accurate hazard maps. Generally, there are inadequate exposures of good sections, poorly known extents of units, and imprecise volumes for deposits. Crisis conditions limit the time available for field and laboratory work. Computer models can simulate possible scenarios, but the volumes,...