Revisiting the Atmospheric Rise Heights of Volcanic Eruption Plumes on Mars

Abstract:

Amanda Meyer, Alexa R. Van Eaton, Larry G. Mastin, Amanda B. Clarke

Evidence for both effusive and explosive volcanism in the geological record of Mars has highlighted questions about the behavior of eruption plumes in the Martian atmosphere. How does the atmospheric structure of Mars (with surface pressures <1% and gravity <40% that of Earth) affect the rise height of volcanic ash and climate-forcing gases? Early modeling studies suggested that Martian plumes may rise significantly higher than their terrestrial equivalents (Wilson and Head, 1994, Rev. Geophys., 32, 221-263), but the validity of these models was called into question by Glaze and Baloga (2002, JGR, 107, 5086). Here we reevaluate the limitations of plume rise models using a steady-state 1-D model for volcanic plumes (Plumeria: Mastin, 2014, JGR, doi:10.1002/2013JD020604). We have used Plumeria to simulate plume heights using a range of atmospheric profiles representing both modern and ‘early’ Mars, and a range of volcanic eruption rates from 1 x 10³ to 1 x 10¹⁰ kg s^-1. The model assumes perfect coupling of particles with the gas phase in the plume (pseudogas assumption), and Stokes number analysis indicates that this is a reasonable assumption for particle diameters less than 5 mm to 1 micron, depending on the eruption rate. Our estimates of local Knudsen numbers support the continuum assumption for this model. Therefore, we suggest that even simplified fluid dynamics models may provide first-order insights into the rise of volcanic gases – and to some extent, fine ash particles – on Mars. Our results show that volcanic plumes in a modern Martian atmosphere may rise three times higher than those from equivalent eruption rates on Earth, potentially reaching 120 km above the surface. We provide a series of new theoretical eruption rate-plume height scaling relationships that may be useful for considering plume injection heights, climate impacts and global-scale ash dispersal patterns (e.g., Kerber et al., 2013, Icarus, 223, 149-156) in Mars’ recent and ancient geological past.