Lava flows in 3D: Using airborne lidar and pre-eruptive topography to evaluate lava flow surface morphology and thickness in Hawai'i

Until recently, lava flow maps have been restricted to two dimensions and, largely, flow outlines rather than internal features. Airborne laser swath mapping (ALSM, or lidar), with its high spatial resolution and intensity data, offers new ways to map lava flows, as demonstrated by recent work in Italy. We extend this approach to Hawai‘i and combine ALSM with preeruptive photogrammetry of the well-observed Mauna Loa 1984 and Kīlauea December 1974 lava flows to map both surface features and along-flow distributions of lava volume. Lidar intensity records progressive biological colonization of flows as a function of both elevation and flow age. Surface roughness can be used to map along-flow variations in flow type (e.g., the pāhoehoe to ‘a‘ā transition) and internal features such as channels and levees, or to develop automated classification schemes. The spatial and volumetric distributions of lava reflect the effusion rate and interactions with topography. Key observations are that the main channel serves to transport, rather than store, lava and that preexisting topography exerts a primary control on the (3D) spatial distribution of individual lava flows. In summary, ALSM data provide new tools for mapping lava flows and new constraints on lava flow emplacement.