Evidence for a Locally Thinned Lithosphere Associated With Recent Volcanism at Aramaiti Corona, Venus

Abstract

Heat flow estimates of terrestrial planets and icy satellites are important for exploring their thermal evolution. Topographic signatures of flexure can be used to estimate the effective elastic lithospheric thickness, he, and heat flow. Here, we use high resolution stereo topography and axisymmetric elastic flexure models to investigate lithospheric flexure around Narina Tholus, a steep‐sided volcanic dome ∼40 km across that superposes the tectonic annulus of Aramaiti Corona. Our results indicate a best‐fit elastic thickness he = 3.9–9.1 km, for values of Young's modulus, E, ranging from 65 to 5 GPa respectively. This suggests a thinned lithosphere locally around Narina Tholus, compared to regional estimates for he. The lower values of E are appropriate to the heavily fractured environment of the corona annulus, and we find that they predict flexural stresses compatible with the limited fracturing observed around Narina Tholus. A global survey yielded 13 additional tholi (or tholi groups) at coronae and with stereo coverage, none of which showed evidence for flexure. We find, that locally at Narina Tholus, the heat flow is elevated by a factor of 2–4 relative to that inferred from a previous study of flexure at Aramaiti, consistent with late‐stage, possibly recent, volcanism focused at, and facilitated by, the fracture annulus. Our results further strengthen arguments for a currently volcanically active planet and demonstrate the role that high‐resolution stereo topography can play in elucidating the current thermal state of Venus.

A Global Survey of Lithospheric Flexure at Steep‐Sided Domical Volcanoes on Venus Reveals Intermediate Elastic Thicknesses

“…The elastic thickness at the location of dome 2 is low: ∼3 km using Cartesian geometry and ∼4 km using axisymmetric geometry. Our low estimate of elastic thickness for the dome agrees with the values of ∼2–3 km from Russell and Johnson (2019, 2021).…”

“…In our analysis, Narina Tholi is referred to as dome 2. We trimmed our profiles to extend ∼100 km from the flexural moat to avoid interfering topography and to match the profiles shown in Russell and Johnson (2019, 2021). These topographic profiles also show signs of lithospheric flexure.…”

“…We reproduced the results around Narina Tholi from Russell and Johnson (2019, 2021). This dome is directly on the margin of Aramaiti Corona and thus has a low elastic thickness.…”

“…Russell and Johnson (2019, 2021) previously studied lithospheric flexure at one steep‐sided dome. Specifically, they obtained topographic profiles radiating from a flexural moat around Narina Tholi.…”

Effects of a Weak Lower Crust on the Flexure of Continental Lithosphere

“…For example, seismic tomography indicates that old, cold, and thick mantle lithosphere does not exist at Lake Bonneville (Austermann et al., 2019; Shen et al., 2013). We propose that the presence of a weak lower crust could be partially responsible for the low inferred values of T e at coronae (Russell & Johnson, 2021) despite the stagnant‐lid convection style of Venus, but future missions will be required to test this hypothesis using seismic tomography.…”