The geometric spectrum of lava domes and spines

Abstract

Extrusion of viscous lava produces domes and spines, collapses of which pose a significant local hazard. Understanding extrusion processes and probabilistic hazard estimation require comprehensive datasets of geometric parameters. We introduce Morphology of Viscous Extrusions (MoVE), a collation of 323 observations of height and width from 80 extrusions at 46 volcanoes globally with compositions spanning basaltic through rhyolitic. Filtering this dataset for sample size, age, and time series overrepresentation reduces the composition range to basaltic-andesitic through dacitic, for which we do not identify a statistically significant effect of composition on extrusion geometry. Young (<200 yr) basaltic or rhyolitic domes are either rare or underrepresented globally. Five well-resolved time series highlight various height-width evolutions and scales possible during growth. Extrusion heights and widths are well-estimated by a Weibull distribution and scale according to a truncated power law; this can guide parameter values used in probabilistic hazard models of collapse-associated pyroclastic density currents.

Keywords

• dome growth
• height
• width
• aspect ratio
• viscous extrusion
• power law