Lava Flow Lobation and Margin Analysis

Graduation date: 2010Comparative investigations based on volcanic morphology suffer from the lack of a large terrestrial baseline for comparison. To fill this gap, the Lava Flow Morphology Database (LAMDA) was proposed as a GIS based central clearinghouse for remote and field investigations of volcanic morphology. This study presents an analysis of LAMDA’S inaugural morphological feature: flow margin lobation. This study measures the margin morphology including the diameter, arc length, lobe height, cleft rate, bulbousness, and cleft angle of 1218 margin flow lobes across 30 lava flows of varied composition. While some lobe features are shown to proportionally increase as compositions become progressively more silicic, other features do not appear to correlate with compositional changes. The ultimate controlling factor behind these morphological changes is flow viscosity and calculations show an excellent correlation with lobe diameter, arc length, and lobe height, as well as a moderate correlation with flow cleft rate. The influence of local dynamics is also examined and local ‘lobe level’ slope, vent distance, and erosional setting are all shown to be only mildly responsible for final margin morphology. This study also examines a hierarchy of margin lobation by measuring margin lobes at multiple scales using a variety of spatial resolution data. Basaltic lava shows lobation at three spatial scales (25m ± 2, 173m ± 16, and 1027m ± 76) while rhyolites only show a single mode of lobation (435m ± 68). Finally, as an example of the utility of this dataset, it is used in three case studies: (1) to inductively compare yield strength equation predictions, (2) to calculate aspect ratios by composition, and (3) to successfully predict the composition of four ‘unknown’ lava flows