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Eruption mechanism plays a large part in the level of hazards a volcano can produce and can also have a tremendous effect on the climate when an eruption column reaches into the stratosphere. The purpose of this study is to refine and produce a methodology using Scanning Electron Microscopy (SEM) and image processing software to characterize ash particle morphology and use that to determine the fragmentation mechanism of any ash deposit. A quantitative method of determining ash morphology and linking it to eruptive styles can be applied to volcanic deposits worldwide and may be used to predict future hazards.The ash samples that are used in this study were collected from tephra deposits on Mount Erebus, Antarctica (< 15 ka), Mt. Redoubt, Alaska (2009), and Taupo, New Zealand (1.8 ka). The Taupo and Redoubt ash represent endmembers of phreatomagmatic and magmatically fragmented plinian eruptions, respectively. The fragmentation mechanism for the Mount Erebus ash is unknown but has been postulated to be a mixture of both phreatomagmatic and magmatic activity (surtseyan and strombolian, respectively). The ash was carefully hand-sieved to ~1mm diameter and imaged by SEM and then processed for morphological properties including rectangularity, circularity, compactness, elongation, solidity, etc. These morphological parameters were used in several statistical analysis to evaluate similarity and differences between deposits and to help constrain fragmentation mechanism.Discriminant analysis on all morphological parameters was found to be the best in separating the data and showing a linear trend between the two fragmentation mechanisms. The separation however, was only achieved after including parameters that are somewhat dependenton vesicle amount, size, and distribution on the particle surface. This analysis also gave further insight to the Erebus tephra which was formed by both mechanisms during a single eruptive pulse. Other separations based on eruption style can also be inferred from this analysis. Regions of wet and dry strombolian style eruptions dominate the right quadrants; whereas, the left quadrants are dominated by phreatomagmatic and magmatic plinian style eruptions. Future deposits could not only verify these regions, but also expand the classification to include other eruption styles (vulcanian and vesuvian).