Introduction: The Magellan mission to Venus [1] revealed the presence of at least 144 large volcanic edifices (i.e., those with flows extending > 100 km in diameter; Figure 1) [2-4]. Numerical models of coupled edifice growth and lithospheric flexure on Venus [5] revealed that horizontal compression in the upper lithosphere gets transmitted into the edifice, tending to halt magma ascent (and th...

Venus, a planet similar to Earth in heat budget lacks plate tectonics, yet displays ample evidence of extensive volcanic and tectonomagmatic processes, including regions large enough to be considered LIPs. Thus Venus provides an excellent opportunity to examine large-scale magmatic processes outside a plate tectonic framework. I discuss four groups of Venus’ largest tectonomagmatic provinces: v...

A long-standing question is whether old oceanic lithosphere continues cooling as the boundary layer of a halfspace or approaches thermal equilibrium, as modeled by a finite thickness plate. Although the latter is the most direct inference from seafloor depths and heat flow, other explanations have been proposed. We investigate this issue using published results for the derivative of the oceanic...

A new shear wave velocity model offshore Southern California is presented that images plate boundary deformation including both thickening and thinning of the crustal and mantle lithosphere at the westernmost edge of the North American continent. The Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment (ALBACORE) ocean bottom seismometer array, t...

S U M M A R Y We use the apparent change in mantle structure beneath the Sierra Nevada since ca. 10 Ma, which suggests convective removal of eclogite-rich mantle lithosphere, and scaling laws developed for Rayleigh–Taylor instability to place constraints on the average viscosity coefficient of the mantle lithosphere. By treating the lithosphere as a non-Newtonian fluid obeying power-law creep w...

S U M M A R Y We describe a method to invert surface wave dispersion data for a model of shear velocities with uncertainties in the crust and uppermost mantle. The inversion is a multistep process, constrained by a priori information, that culminates in a Markov-chain Monte-Carlo sampling of model space to yield an ensemble of acceptable models at each spatial node. The model is radially anisot...

Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmati...

[1] The boundary of the Martian crustal dichotomy in the eastern hemisphere is one of the most striking topographic features on the planet. The long wavelength topography of much of the boundary is expressed by a broad rise and an arched ramp that slopes downward from the southern highlands into the northern lowlands and often ends in a steep scarp. Lithospheric flexure of the southern highland...

Numerical experiments reproduce the fundamental architecture of magma-poor rifted margins such as the Iberian or Alpine margins if the lithosphere has a weak mid-crustal channel on top of strong lower crust and a horizontal thermal weakness in the rift center. During model extension, the upper crust undergoes distributed collapse into the rift center where the thermally weakened portion of the ...

We examine a number of first order features of Pannonian basin evolution in terms of the feedback relation between passive far-field induced extension and active Raleigh-Taylor instable upwelling of the asthenosphere. We show that active mantle upwelling following a phase of passive extension are viable mechanisms explaining the Pannonian basin formation. The dynamic interplay between far-field...