Figure 9

Relative proportions of simple and complex ash particles as a function of distance from source for the May 18, 1980 Mount St. Helens samples. Blue diamonds represent the simple ash particles while red squares represent the complex ash particles. Although both simple and complex ash particles exist in all locations, the weight fraction of complex ash particles falls from 90% to 40% at the most distal collection location due to their generally larger size compared to simple ash particles. The grey curves indicate the probability distribution function of the two morphological types with distance from source.