The planet venus displays a panoply of striking volcano-tectonic structures, including broad volcanic edifices and radiating fracture systems. In previous NASA-supported efforts, we have explored…

This is a grant awarded by the National Aeronautics and Space Administration (NASA) Shared Services Center to the Universities Space Research Association (USRA), a nonprofit organization, to conduct research related to planetary volcanism on Venus. The contract has a potential value of $424,235.20 and was awarded on January 1, 2018, with a completion date of September 2, 2022. The research aims to improve understanding of the mechanics of magma transport, storage, and emplacement on Venus, and the resulting volcano-tectonic structures, by developing advanced finite element numerical models. The proposed work involves two main tasks: 1) constructing models of volcanic edifices and their supporting lithospheres to understand how the time-dependent emplacement of volcanic units controls stress history, and 2) evaluating the stress states generated and their implications for magma storage, ascent, intrusion, and extrusion. This research is directly relevant to NASA's Science Mission Directorate goals of understanding planetary interiors, lithospheres, volcanism, and surface evolution.

The planet venus displays a panoply of striking volcano-tectonic structures, including broad volcanic edifices and radiating fracture systems. In previous NASA-supported efforts, we have explored the mechanics of magma transport, storage, and emplacement on venus in relation to lithospheric stress states from flexural loading. This work has yielded fundamental new insights into the evolution of volcanic systems, such as the first scenario for producing venus s radiating dike systems from realistically loaded magma chambers. However, our investigations have focused exclusively upon reservoirs located in the sub-edifice substrate (the lithosphere), and have revealed a critical obstacle that inhibits our ability to understand volcano-tectonic features on venus. Elastic models of large edifices that induce substantial lithospheric flexure require first-order assumptions concerning the edifice stress state that, in combination with flexural loading stresses, inhibit transport of magma to the surface and creation of the types of circumferential and radial tectonic structures seen on volcanoes on venus. To better understand the evolution of stresses within and beneath an edifice as IT grows, we need to move beyond these limitations. To this end, we propose an advanced program of finite element numerical modeling designed to examine the time-dependent stress and deformation of lithosphere subjected to extrusive and intrusive modes of volcanic loading. The proposed work comprises two tasks. In the first task, we will construct finite element models of volcanic edifices and their supporting lithospheres, in order to understand how the time-dependent emplacement of predetermined volcanic units at the surface (via in-progress additions to finite element meshes) controls the stress history within and beneath the edifice. Of necessity, this process must incorporate stress-mitigating effects such as faulting (via plasticity), and time-dependent ductile flow (via viscoelasticity). While initial models will be developed without eruptible magma reservoirs, reflecting the brevity of such features within long-lived volcanic systems, the mechanical and thermal effects of intrusive bodies will be incorporated later via appropriate adjustments of model domains and boundary conditions at specific time steps, simulating transition from a stable thermal mush to an eruptible, mostly liquid magma. In the second task, we will evaluate the stress states generated in the first task and their implications for magma storage (chambers), ascent, intrusion (sills and dikes) and extrusion (e.g., edifice construction), and thermal state. Stress fields from task 1 and magma properties (density, viscosity) will be inputs to equations for magma movement velocity in dikes and sills, in order to determine magma movement paths within the lithosphere, and these magma pathways will in turn dictate where (if) material erupts and hence the surface loading that occurs, which feeds back into the stress state controlling subsequent eruptions. In this way, we will let the magma decide how growth of the edifice, and thereby the stress history, evolves. We will interpret specific models from task 1 in terms of sustainability of magma pathways and changes in intrusion geometry or edifice shape. By comparing the results to existing venusian volcano-tectonic features e.g. conical and flat-topped volcanoes, various coronae we can constrain the effects of parameters such as lithosphere thickness, magma supply rate, and magma source dimensions on the eruptive, intrusive, and thermal histories of the resulting systems, with implications for the geological and geophysical history of the host regions of venus. The proposed work is relevant to SSW program goals of understanding phenomena affecting the surfaces and interiors of planets, specifically addressing called-out research areas in interior structure, lithospheres, volcanism, and evolution and modification of surfaces.