Search

Venus is a terrestrial planet with dimensions similar to the Earth, but a vastly different geodynamic evolution, with recent studies debating the occurrence and extent of tectonic‐like processes happening on the planet. The precious direct data that we have for Venus is very little, and there are only few numerical modeling studies concerning lithospheric‐scale processes. However, the use of numerical models has proven crucial for our understanding of large‐scale geodynamic processes of the Earth. Therefore, here we adapt 2D thermomechanical numerical models of rifting on Earth to Venus to study how the observed rifting structures on the Venusian surface could have been formed. More specifically, we aim to investigate how rifting evolves under the Venusian surface conditions and the proposed lithospheric structure. Our results show that a strong crustal rheology such as diabase is needed to localize strain and to develop a rift under the high surface temperature and pressure of Venus. The evolution of the rift formation is predominantly controlled by the crustal thickness, with a 25 km‐thick diabase crust required to produce mantle upwelling and melting. The surface topography produced by our models fits well with the topography profiles of the Ganis and Devana Chasmata for different crustal thicknesses. We therefore speculate that the difference in these rift features on Venus could be due to different crustal thicknesses. Based on the estimated heat flux of Venus, our models indicate that a crust with a global average lower than 35 km is the most likely crustal thickness on Venus. Plain Language Summary: Venus is a planet that is roughly the same size as the Earth, and recent studies have debated the style of Venusian tectonics and how it differs from Earth. One such tectonic process is known as "rifting," where a tectonic plate gets extended and forms structures as in East Africa on Earth. These rift structures have been observed on Venus as well, but it is unclear how they formed under Venus' high surface temperature and pressure. Computer simulations have improved our understanding of the rifting process on Earth, so here we apply them to Venus to discover how rifting processes work under Venusian conditions. Our results show that the crust needs to consist of strong rocks in order for rifting to take place under Venus' conditions. The thickness of the crust also has a direct effect on the evolution of the rift and a thin crust favors the production of magma on Venus. We compare the surface topography of the rifts in our simulations with rift topographies observed on Venus. We find that different crustal thicknesses fit different rift observations on Venus. Therefore, we speculate that differences in rifts on Venus could be related to differences in the crustal thickness. Key Points: A strong crustal diabase rheology is required to localize strain and develop rifts in our modelsA thin crust produces the melt required to support the hypothesis of Venus being currently volcanically activeCrustal thicknesses of 25 and 35 km result in surface topographies comparable with rift topography observations of Venus [ABSTRACT FROM AUTHOR]

Passive margins may undergo multiple phases of extension with distinct structural, petrological and sedimentary processes before achieving breakup. Observations of rift axis migration through time may reflect cooling, hardening and subsequent abandonment of the rift axis during either long-term periods of slow extension or periods of tectonic quiescence. Here, we use 2D thermo-mechanical numerical models to examine rift reactivation and migration during multiphase extension where a period of tectonic quiescence separates phases of extension. Our goals are to identify the rheological mechanism(s) controlling rift reactivation versus migration and determine if cooling phases may help explain recent interpretations of passive margin architecture and evolution. Our numerical experiments indicate that the relative integrated brittle strength between the initial rift and surrounding regions, rather than the total integrated strength, largely controls rift reactivation versus migration. The tectonic quiescence (cooling) duration required to induce rift migration ranges between 20 and 60 Myr (minimum bounds). This range reflects variations in extension velocity, magnitude of shear zone healing, crustal rheology and asthenospheric rheology. Reactivated rifts after extensive (>20 Myr) cooling periods in some cases develop asymmetric margins with deformation patterns stepping toward the future rift, such as characterizing most of the Atlantic conjugate margins. [ABSTRACT FROM AUTHOR]

Detachment of the deeper part of subducted lithosphere causes changes in a subduction zone system which may be observed on the Earth''s surface. Constraints on the expected magnitudes of these surface effects can aid in the interpretation of geological observations near convergent plate margins where detachment is expected. In this study, we quantify surface deformation caused by detachment of subducted lithosphere. We determine the range of displacement magnitudes which can be associated with slab detachment using numerical models. The lithospheric plates in our models have an effective elastic thickness, which provides an upper bound for rapid processes, like slab detachment, to the surface deformation of lithosphere with a more realistic rheology. The surface topography which develops during subduction is compared with the topography shortly after detachment is imposed. Subduction with a non-migrating trench system followed by detachment leads to a maximum surface uplift of 2–6 km, while this may be higher for the case of roll-back preceding detachment. In the latter situation, the back-arc basin may experience a phase of compression after detachment. Within the context of our elastic model, the surface uplift resulting from slab detachment is sensitive to the depth of detachment, a change in friction on the subduction fault during detachment and viscous stresses generated by sinking of the detached part of the slab. Overall, surface uplift of these magnitudes is not diagnostic of slab detachment since variations during ongoing subduction may result in similar vertical surface displacements. [Copyright &y& Elsevier]

Examines the vertical surface displacement at convergent plate margins. Velocity of the surface plates; Evolution of the subduction zone system; Increase in friction along the subduction fault.

The article discusses how hot material arising from Earth's interior affected by plate tectonics produces irregularities in Earth's topography and assists in break-up of continental plates as seen in computer models.Topics discussed include break -up of continental plates, plumes , 3D computer models for plume-lithosphere interactions. Different regions like Central Atlantic Ocean, Iberia and Newfoundland and Norway and Greenland affected by this phenomena are discussed.