A Multi-instrument Investigation of Volcanic Lava Flow Structures and the Effects on Satellite Derived Products

Volcanism is a lower-frequency, high-consequence geologic event affecting an increasing number of populations in proximity to active volcanoes. With the collection of higher spatial resolution satellite data, the evaluation of the topography, structure, and properties of lava flow surfaces, which can be highly variable and difficult to access, provides the detail necessary to improve our understanding of these events and the potential propagation paths. This multi-instrument approach combines WorldView-2 visible imagery, ASTER visible and thermal data, and ICESat-2 ATL08 land and vegetation products to investigate the flow properties in the Mauna Loa, Kilauea, and Mauna Ulu flow fields of Hawaii. The goals focused on investigating (1) the ICESat-2 lidar signal response over lava flows accounting for reflectance and roughness parameters, (2) the effect of flow structures such as roughness on ASTER thermal derived products, and (3) the ability to quantify the presence and effect of vegetation on surface characterization. Visible data were utilized to evaluate the reflectance properties and identify vegetation on the flow surfaces or along boundaries, while apparent thermal inertia (ATI) and temperature products were derived from thermal data. ICESat-2 ATL08 (version 5) ground labeled photons were evaluated to separate flow morphologies and quantify the average surface roughness of each flow. The identified photon density (per m along-track) for each flow reveals a strong correlation between ICESat-2 signal response and flow age/morphology due to differences in reflectance and surface structure. Comparison of the ICESat-2 derived roughness and topographic characteristics with ASTER derived temperature and ATI establishes unique trends such as lower temperatures for rougher surfaces. ICESat-2 ATL08 labeled ground and vegetation photons used to quantify the physical extents of any vegetation present, including height, photon density, and coverage percentage, on or around these surfaces demonstrated an effect on the derived thermal products. This multi-instrument remote sensing application provides a unique opportunity to advance the current extraction methodology for flow surface structure, which are critical to evaluate eruption characteristics and future flow propagation modeling.