Surface unit characterization of the Mauna Ulu flow field, Kilauea Volcano, Hawai′i, using integrated field and remote sensing analyses

Investigation of surface units in the Mauna Ulu flow field, Kilauea Volcano, Hawai′i, was conducted through field and remote sensing analyses. Recently acquired Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and MASTER (MODIS/ASTER airborne simulator) datasets, which cover the visible- through thermal-wavelength region, have been analyzed and correlated with a field-based characterization of Mauna Ulu flow-unit surfaces. Field observations were made of unit morphologies (decimeter- to decameter-scale) as well as small-scale (millimeter- to centimeter-scale) surface textures. Estimates were made of the extent of surface crust spallation, as well as the abundance of vesicles and phenocrysts on the surface crust and spallation surfaces. The field-based characteristics were compared with remote sensing data, including visible and near-infrared reflectance spectra, thermal infrared emissivity spectra, and emissivity-derived small-scale roughness. Visible-wavelength characteristics are controlled primarily by color, luster, and decimeter- to meter-scale surface irregularities, whereas thermal-wavelength characteristics are primarily controlled by the abundance of small-scale roughness elements such as vesicles. Although individual data pixels are not of sufficient resolution to identify typical individual lava flow units using point spectra, mean spectra allow characterization of unit surface crusts. Flow-unit morphologies and surface textures are related to differences in emplacement and post-emplacement modification of ′a′a and pahoehoe lobes. Pahoehoe surface properties reflect the flow regime during emplacement and the history of cooling, degassing, and crystal formation/settling. The nature of pahoehoe surface crusts indicates that within the wide range of emplacement conditions expressed within the flow field, two sets of conditions are dominant, producing a bronzy, smooth crust or a dark, rough crust. The former makes up the majority of the pahoehoe surfaces and reflects minimal cooling and degassing prior to emplacement, whereas the latter reflects cooling and crystallization during storage within the flow field. This study provides a detailed characterization of Mauna Ulu surface units, and presents an integrated field and remote sensing approach to mapping and interpreting the emplacement of lava flow fields.