Modeling the dynamics of dense pyroclastic flows on Venus: insights into
pyroclastic eruptions
Abstract
On Venus, relatively young deposits near volcanic and coronal summits
with unique radar characteristics have been proposed to be emplaced by
pyroclastic density currents (PDCs). The proposed units are laterally
extensive, long-runout deposits showing moderate to high radar
backscatter and circular polarization ratio in 12.6 cm wavelength
synthetic aperture radar data. Previous studies have hypothesized that a
recent resumption in volcanism activity in the form of PDC-forming
eruptions could have emplaced these deposits. We model the dynamics of
dense PDCs using a 2D, depth-averaged framework focusing on regions
where stereo-derived topography coverage is available; this includes the
flanks of Irnini Mons, Anala Mons, Didilia Corona and Pavlova Corona.
Two different mechanisms of initiation— impulsive collapse of an
eruption column and sustained pyroclastic fountaining — are
considered. The results emphasize the importance of pyroclastic flow
fluidization via high pore pressure in emplacing long-runout deposits
along gently sloping (< 2°) volcanic flanks. We also show that
collapse of columns >1.2 – 1.4 km tall as well as
pyroclastic fountains lasting >400 s with fountain heights
of 50 m are capable of generating pyroclastic flows that could emplace
some of the smaller deposits studied. For the large deposits at Irnini
Mons, more energetic flows resulting from taller column heights would be
necessary; the dynamics of such flows under Venus’s conditions are not
well understood. Distinguishing between the two initiation styles —
column collapse and sustained fountaining — is not feasible with
currently available datasets and would require higher resolution imagery
and topography data.