Visualising active volcanism with high spatial resolution satellite data: the 1991-1993 eruption of Mount Etna
We present seven Landsat Thematic Mapper (TM) images that document the period before, during and after the 1991-1993 eruption of Mount Etna. This episode remains the most volumetrically significant to occur at the volcano within the past 300 years. We show how TM data can be used to identify major changes in the lava flow regime, specifically the transition between channel and tube-fed flow conditions, by mapping changes in the radiant properties of the flow surface. The high spatial resolution of TM (30-m pixels) allows point sources of radiance, such as skylights and tumuli, to be distinguished from linear radiant features such as surface lava flows. Using this information we illustrate the spatial and temporal development of a major tube system that developed within the flow-field. Detailed field maps of the tube system compiled by Calvari and Pinkerton (1998) allow us to validate the accuracy of our interpretations, and lead us to conclude that TM can be used to infer the position of tubes within the active flow-field to a reasonable level of accuracy. This indicates that similar high spatial resolution data could be used as a stand-alone tool to provide timely information regarding tube formation at future eruptions, useful information given that tubes can be a major factor in determining, for a given effusion rate, how far lava flows. When draped over a digital elevation model, the thermal data not only portray the nature of the relationship between flow surface structure and regional topography, but also provide a unique visualisation of how the flow-field advanced and threatened to inundate the town of Zafferana before, ultimately, being diverted.