Table 1: The total volume and mass of the August 19, 1992 Crater Peak/Spurr volcanic cloud as determined by the two methods outlined in this paper. Both methods assume a constant eruption rate and that the eruption lasted for 3.5 hours. The extent of the volcanic cloud was determined by using a scattering index threshold value of 10. The theoretical method uses a lognormal particle distribution with a mean of 0.9 mm, a standard deviation of 0.74, and a particle fall out time of half an hour. The empirical method is based on a modified rainfall rate with a correction factor of 0.42. The last column lists the estimated volume and mass based on ground sampling of the ashfall blanket[Neal et al., 1995].