YOU KNOW WHAT YOU DO WHEN YOU ASSUME: MODELING BASALTIC ERUPTION PROCESSES (Invited Presentation)

Active volcanic eruptions are rarely observed within our Solar System: even on Earth, most volcanic eruptions occur in remote locations (including underwater) where eruption processes cannot be witnessed in real time. Volcanologists have developed countless models that translate the morphologies of volcanic deposits (lava flows and pyroclastics) into eruption and emplacement parameters, including the rheology and composition of the erupting magma. Best practices require that model results be tested against field data, but even the most basic field data can be difficult to obtain.

All extraterrestrial volcanic deposits, and most terrestrial submarine ones, must be understood through remotely collected data. Data sets that volcanologists use to interpret volcanic deposits include visible imagery, compositional data through spectroscopy (using visible, infrared and ultraviolet wavelengths) and topography (although knowledge of pre-eruption topography is rare); less commonly, such as for the surface of Venus, radar data are used. Even as technologic advances improve spatial and spectral resolution, volcanic morphologies may be obscured by regolith, dust, sediment or soil. The surfaces of all solid bodies undergo some type of weathering that modifies primary morphologies with time. Can we be certain, for example, that the deposit observed on Mars is composed of eroded, variably indurated ignimbrites—or could it be a stack of weathered lava flows?

Volcanologists have used countless models to constrain eruption and emplacement parameters from the resulting deposits and morphologies. Many commonly used models require debilitating assumptions (e.g., a single width applied to a lava flow whose width clearly varies over distance, or a “Newtonian fluid” for a lava flow displaying deformation of a solid crust) or general assumptions about composition or rheology (e.g., “tholeiitic basalt”). Extraterrestrial data are sufficiently incomplete that the existing models—even sophisticated computational fluid dynamics models—need assumptions. Well-documented terrestrial eruptions and laboratory simulations are essential for testing the accuracy and sensitivity of available models so that these models can be applied (with appropriate restraint) to improve our understanding of volcanologic behaviors on Earth and other planetary bodies.