WEATHERING OF VOLCANIC ASH FROM DIFFERENT CLIMATES USING SECONDARY ELECTRON ANALYSIS

Volcanic ash begins to weather upon deposition, a complex process resulting in the devitrification of glass and the deposition of clay minerals within the pore spaces of volcanic material. In order to categorize the degree of weathering, a sample can be compared to a classification scheme. The existing weathering classification scheme developed by Almquist (2011) and O’Dowd (2017) consists of volcanic material analyzed by SEM and XRD from the Waipaoa catchment in New Zealand, the 1980 eruption of Mount St. Helens, and Cobble Cuesta, NV. This scheme shows not only the variation in weathering between terrestrial and marine deposits, but also length of time since eruption. We are examining four additional samples consisting of material from the San Francisco Peaks, AZ; San Pedro Mountains, Chile; Mount St. Helens, OR (pre-1980); and the Bandelier Tuff, NM. Samples were collected, prepared, and analyzed on an SEM. These results were then compared and related to their depositional environments and time of deposition. This allows a broadening of the classification scheme in order to enhance it as a tool for researchers to categorize the extent of weathering of volcanic materials.