THE LAVA MORPHOLOGY DATABASE (LAMDA)

Most of the inferences about the dynamics of extraterrestrial lava flows have been obtained through the interpretation of flow morphologies using terrestrial analogs, fluid models, and laboratory comparisons to constrain lava viscosity, temperature, and effusion rate. Even magma chamber and vent dimensions have been inferred from surface flow features. To date, however, morphological studies of terrestrial lava flows have predominantly focused on a single feature or on a limited subset of terrestrial flows and have employed a wide variety of methodologies. This project is an attempt to standardize this type of analysis through the creation of a terrestrial ‘lava morphology database’ (LAMDA). Once calibrated on sufficient terrestrial flows, this database will be a useful resource to the larger planetary volcanism community and increase the veracity of future interpretations based on lava flow morphology.

To that end, we have been measuring features visible in remotely sensed data using GIS to cross compare multiple datasets. Where visible, features measured include: vent diameter, flow distance (vent to furthest margin), surface area, aspect ratio, the radius of margin lobation curvature, height, and arc-length, flow surface ridging wavelength, local slope, etc. LAMDA’s underlying goal is to further studies that have worked to quantify the impact of slope, rheology, and effusion rate on final emplacement morphology. Proof of concept work on nine lava flows spanning the compositional range from basaltic (50% SiO₂) to rhyolitic (72% SiO₂) confirm the Wadge and Lopes (Bul. Volc, 1991) results showing that lobation size, height, and spatial density are related to each other and to flow composition through yield strength. This initial analysis also showed that flow margin lobes appeared to naturally group into a three-level hierarchy of lobation sizes (I - ~1000m, II - ~200-300m, III - ~20-70m) with only mafic compositions resulting in lobation at all levels. We will present results of the second phase of this study, a calibration dataset of 80 additional lava flows at 36 terrestrial volcanoes of similarly varied composition, as well as the results of a second field expedition to quantify LAMDA’s error margins.