HOW DO CHANNELIZED LAVA FLOWS PROPAGATE IN THE VENUSIAN ENVIRONMENT?

Volcanism was (and potentially still is) an important process that shapes the Venus surface. This is evident by the diverse assortment of volcanic features and lava flow morphologies observed globally during the Magellan and Venus Express missions. Specific lava flow morphologies (channelized flows with levees, canali, and lobes) have been identified in several volcanic regions (e.g. Mylitta Fluctus, Tuli Mons, and Turgmam Fluctus). These Venusian flow morphologies are similar to those observed on Earth and Mars. However, one key difference is the extreme environment of Venus. How does such a hot and dense atmosphere influence the emplacement of Venusian lava flows?

In this study, we quantify the impact of Venusian planetary (gravity) and environmental conditions (atmospheric temperature, composition, and density) on the propagation of a channelized lava flow using the PyFLOWGO thermorheological model for channelized flows. Using the model and a starting example composition (the 1975 Tolbachik eruption, Russia), we incrementally adapt that basaltic lava flow to Venus conditions. At each step, model parameters that affect the flow’s thermorheologic evolution are changed and their impact quantified.

The lower gravity, the higher atmospheric temperature, and CO₂-rich atmosphere all promote the formation of longer lava flows where compared to the equivalent terrestrial flow. The increase in flow length is primarily due to less convective and radiative heat loss into the surrounding atmosphere. The environmental condition that has the largest impact on a channelized lava flows progression, however, is the atmospheric density. The high atmospheric density of Venus improves the efficiency of conductive heat loss by ~15 times more than the equivalent flow on Earth. The increased heat loss caused by the high atmospheric density has the opposite effect, resulting in a faster-cooling flow that is ~50% shorter. Results of the modeling suggest that flows on Venus will cool more rapidly than those with the same scale and effusion rate on Earth.