Hot and Cold Topography: Volcanic Processes on Venus and Airy Isostasy in Icy Shells of Ocean Worlds

Geologic activity, largely driven by outward movement of internal thermal energy, forms an intricate link between the characteristics of a planetary body’s surface and its internal dynamics. This work explores this relationship using a range of proven methodologies. In the first project, I investigate lava flows associated with two quasicircular volcano-tectonic features on Venus, known as coronae. Despite the ongoing debates over their formation mechanism and the difficulty geophysical models face in reproducing these features, my research offers new insights into their formation. Through geospatial analysis of synthetic aperture radar and altimetry data, I quantify the alterations in the topographic orientation since the emplacement of lava flows. My findings reveal significant changes in topographic orientation resulting from shifting magma sources. Expanding on this work, the second project involves a global survey of coronae on Venus, particularly focusing on those with lava flows within their fracture annulus that diverge from the downhill direction. The spatial distribution of these unique coronae offers insights into whether flow divergence is a widespread phenomenon, exclusive to a specific region, or randomly found throughout the coronae population. Utilizing spherical harmonic analysis, I compare the spectral power of divergent coronae with that of the entire coronae dataset, and the distribution of coronae to a comprehensive catalogue of volcanoes and topography. I find that the phenomenon of lava flow divergence is not regional but is nonrandom, and it follows the same distribution as the full corona population. Furthermore, I find that coronae and volcanoes share the same characteristics in their long-wavelength distribution. This comparison further emphasizes the volcanic nature of coronae, supporting the conclusions drawn from the first project. In the final project, I explore the ability of icy shells to support topography via Airy isostasy. Buoyant support of topography is often assumed to be the prevailing mechanism in icy shells of ocean worlds across the entire spectrum of wavelengths. I simulate the evolution of topography from short to hemispheric wavelengths over geologic time scales. I find that buoyant support is only applicable for topography at the longest wavelengths. The nuanced relationship between buoyant support and topography involves contributions from lithospheric strength and channelized flow that need to be considered when estimating shell thickness at regional and local scales.