Expanding the database on basaltic volcanic ash: single explosion samples from Stromboli in 2002

Past work on vesicle textures in lapilli collected at Stromboli during different time periods highlighted a link between vesiculation dynamics and small scale variations in explosion intensity (Lautze and Houghton, 2005, 2007, 2008). Our more recent work has looked at the characteristics of smaller, ash-sized, tephra that are more accessible for real-time sampling and holds complementary information. The quantitative parameterization of ash particle textures is relatively nascent, because its small size has made it inherently difficult to analyze quantitatively. Modern analysis software, linked to a Scanning Electron Microscope (SEM) at the Istituto Nazionale di Geofisica e Volcanologia (INGV) in Rome, has enabled efficient gathering of morphoscopy and surface chemistry data for 100s of individual ash-sized particles. Such data has been presented for, e.g., Etna and Stromboli volcanoes (Lautze et al., 2012; in press). Here we present data from individual explosions at Stromboli in May and Sept 2002, which is compared to similar data (in press) on ash collected at Stromboli in Oct 2009. Our observations suggest May 2002 explosions were relatively weak, ash-rich, Sept 2002 explosions were more powerful and mostly spatter-rich, and Oct 2009 explosions were the most frequent and powerful explosions with a mixture of ash and spatter. Differences in shape, texture and surface chemistry among the ash samples collected from the different time periods at Stromboli can be linked to parameters such as variable supply of gas-rich magma, openness of the conduit system, and atmospheric transport dynamics. The data presented will contribute to a growing database on volcanic ash, which in the future should be expanded to include information on more silicic systems as well.