Morphometry of lava flow units over LIDAR-derived topography at Mount Etna: relationship with lava supply

High resolution, LIDAR-derived digital elevation models of volcanic areas can significantly improve knowledge of lava flow morphology and emplacement mechanisms. Here we focus on single flow units, applying a new semi-automatic procedure which provides a quantitative analysis of their shape. The method relies on the automatic processing of the elevation profiles obtained on transects orthogonal to the flow unit axis. We apply the procedure on both active and inactive lava flow units recently emplaced at Mount Etna. The main topographic datasets used are high-resolution digital elevation models obtained from multitemporal LIDAR surveys. Starting from the axis of a lava flow unit, our method yields morphometric data on the flow unit at small spacing, calculating parameters including flow width, channel width, the heights of the levees, inward and outward slope of levees, and estimating pre-emplacement slope along the axis. The procedure is embedded in a customized GIS, which allows easy processing, handling and displaying of data. Our results show that the channel width accommodates first-order trends of the pre-emplacement slope along the flow unit axis, while it is little affected by high frequency changes in slope; in contrast, flow unit width and flow unit thickness are apparently influenced by small-scale changes in slope. By processing the different time-steps of the multitemporal LIDAR acquisitions, we quantified lava supply rates within given time intervals for some of the processed flow units. Combining this knowledge with measured morphologies, we explore the existing relationship between these two features.